# AGM batteries: Someone using them?



## PCP (Dec 1, 2004)

AGM batteries have a big defect, they are expensive but have many advantages and mainly two that make them very interesting for cruisers:

1 – They lose very little charge so they can be let alone with minimum maintenance if you don’t use the boat in the winter.

2 – And main advantage, they charge 3 times faster than normal batteries.

Providing you have a big enough alternator this means that you have to run the engine for 3 times less hours (for charging) than with regular batteries. This is a huge advantage and will make them not expensive at all because the running hours of the engine are expensive. Of course the main advantage is that you gain a much bigger electric autonomy on your boat.

Well, this is what I have read and it is consensual but I would like to know if someone is using them and if this works out like that in reality, meaning if there really are a big difference in charging time?

..


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## Minnewaska (Feb 21, 2010)

I have them and like them specifically because they hold a charge longer when stored over the winter. I have 13 batts in total (4 house), so it's impossible to take them out and leave them on a trickle charger all winter. I head out about every 6 weeks and top off.


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## mightyhorton (Dec 3, 2006)

If you don't like running your engine to charge your batteries, the fast charge thing is huge. In the Sea of Cortez and Banderas Bay, where it is almost always cloud free, you can keep them charged just with solar panels, even running refrigeration and making ice, nav gear, lights, stereo, water makers, etc.

Their initial and replacement cost is horrible if you are retired and cruising. One of my pals is trying to figure out where he is going to come up with $6k for a new AGM battery bank.....

Ian


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## PCP (Dec 1, 2004)

mightyhorton said:


> ....
> 
> Their initial and replacement cost is horrible if you are retired and cruising. One of my pals is trying to figure out where he is going to come up with $6k for a new AGM battery bank.....
> 
> Ian


That should be a huge bank of batteries. For what I have heard they cost about 3 times more than regular batteries.

Regards

Paulo


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## Paul_L (Sep 16, 2004)

PCP said:


> ...
> 2 - And main advantage, they charge 3 times faster than normal batteries.
> ....


This just doesn't happen in practice. The acceptance rate is definitely higher, but the last 10 to 15% charge is still going to be at low rates. AGMs need to be 100% charged periodically, so you can't just stop at 90% full.


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## PCP (Dec 1, 2004)

Paul_L said:


> This just doesn't happen in practice. The acceptance rate is definitely higher, but the last 10 to 15% charge is still going to be at low rates. AGMs need to be 100% charged periodically, so you can't just stop at 90% full.


You have them or work with them and that statment results from personal experience or is just your opinion?

Regards

Paulo


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## HMoll (Sep 18, 2007)

Paulo,

I never had lead acid or lead. When I bought my boat, and studied a bit, aside from cost, AGM was a no brainer. They lasted four years, and my use was very irregular. Last year, I upsized my battery bank to (7) 105Ah battery bank, AGM. I run a 10,000BTU air conditioner with it. Love it, no genset. Turns out that my engine is quieter than my single-cylinder genset too. Another advantage is that AGMs are sealed, zero maintenance and zero gas emmissions from what I have read. Good AGM bank and large alternator. More than enough for your refrigeration. Do the numbers. Good luck!


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## HMoll (Sep 18, 2007)

BTW, cant wait till LiIon come down in cost!


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## Maine Sail (Jan 6, 2003)

HMoll said:


> Paulo,
> 
> I never had lead acid or lead. When I bought my boat, and studied a bit, aside from cost, AGM was a no brainer. They lasted four years, and my use was very irregular. Last year, I upsized my battery bank to (7) 105Ah battery bank, AGM. I run a 10,000BTU air conditioner with it. Love it, no genset. Turns out that my engine is quieter than my single-cylinder genset too. Another advantage is that AGMs are sealed, zero maintenance and zero gas emmissions from what I have read. Good AGM bank and large alternator. More than enough for your refrigeration. Do the numbers. Good luck!


AGM IS.......lead acid......... They can also vent gas if over charged, and when they do, the lost electrolyte can not be replaced.

If your bank of AGM batteries is made by Lifeline they are not maintenance free and need to be equalized occasionally, or as Lifeline calls it "conditioned", at 15.5V temp compensated for about 8 hours, especially if you are a cruiser.

My experiences with AGM, to summarize, are that:

They cost a lot more
Have shorter cycle life
Accept more current than wet lead acid
When they fail they tend to fail with little to no warning
Need to be charged to 100% SOC as often as possible

My experiences & thoughts.....

*AGM's Making The Choice (LINK)*


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## PCP (Dec 1, 2004)

HMoll said:


> Paulo,
> 
> I never had lead acid or lead. When I bought my boat, and studied a bit, aside from cost, AGM was a no brainer. They lasted four years, and my use was very irregular. Last year, I upsized my battery bank to (7) 105Ah battery bank, AGM. I run a 10,000BTU air conditioner with it. Love it, no genset. Turns out that my engine is quieter than my single-cylinder genset too. Another advantage is that AGMs are sealed, zero maintenance and zero gas emmissions from what I have read. Good AGM bank and large alternator. More than enough for your refrigeration. Do the numbers. Good luck!


Thanks! Yes I have done the math and it looks good on paper, just wanted someone that uses them to confirm that on the reality. It seems that you have done just that

Just a last question: For your 735Ah battery bank what is the power of the alternator you use to charge them, the one on the engine?

Regards

Paulo


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## chef2sail (Nov 27, 2007)

I have 6 -6 volt Lifeline AGM. 720 ah. I do "equalize or condition as Maine sail recommended. Also based on his recommendation I outfitted with an Electromax 120 with serp belt and Maxx regulator with appropruiate temp sensor. Important with the large battery bank to charge to not run the alternator at such a hig charge to get to 85% for a long time. If you go the large amp hr route make sure you also upgrade the alternor or you will burn it out.

Lifeline AGM supposed can be charged over 1000 cycle I am going on 4 years now with mine with never a problem. Also check the arrenty. I know its par rated by some is better than 0

My advantages.- 
6 volts easier to pick up than 8D.
No maintainence except equalizing- and they are in a tough sopt n the boat to get to
They can be stacked on their sides or many configuations
Somne of them (Kifeline) mastervolt have low profiles
Accept a charge more quickly

Price the Lifelines many places as the prices really vary greatly. Some have free shipping. You can by many 6 volt cheaper,,,for sure,,,but the time for maintainence and such may not be worth it for you.

Dave


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## PCP (Dec 1, 2004)

Maine Sail said:


> AGM IS.......lead acid......... They can also vent gas if over charged, and when they do, the lost electrolyte can not be replaced.
> 
> If your bank of AGM batteries is made by Lifeline they are not maintenance free and need to be equalized occasionally, or as Lifeline calls it "conditioned", at 15.5V temp compensated for about 8 hours, especially if you are a cruiser.
> 
> ...


Thanks for the link

But even after reading your comments I still think that AGM makes sense to my case.

The bank will have a max of 360-120ah and the alternator has 120amp. I plan to add a hydrogenerator good for 300/500w on most sailing conditions.

Do I need to anything more to regulate the system (letting out the hydrogenerator for now), or the 120 amp alternator will be enough?

Regarding costs, the alternative is to buy a generator and that costs several times the price of the batteries (8 000€) and has an expensive maintenance. Even with the batteries lasting 3 to four seasons I guess it will be less expensive than the generator, less noisy and will save the space needed for the generator.

I want to use them because I want to stay at anchor for about 15 days and then go to a marina for water and for 100% charge on the batteries. I don't have AC and have diesel heating so much of the energy required is for running 2 refrigerators (plus some light and eventually some music).

It makes sense? Comments please

Regards

Paulo


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## Shortman (Feb 12, 2006)

Got two 105AH Lifelines for my Pearson 34 Spring 2006 and been quite happy with them. 80A alternator & next to never run engine to only charge batteries. Trickle charge w/20W solar panel. But I am also a power miser. Biggest draw is GPS & autopilot, radar when foggy (oh, never in Maine), although fog often coincides w.motoring.
Leave in place over winter, charge fall, charge spring.


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## sawingknots (Feb 24, 2005)

i have a lifeline gpl 8dl battery and a morningstar controler pro 30 but lack enough solar panels,the controler won't allow the battery charge to get too low and when my rich uncle gets out of the poor house i'll add more panels,i have a seperate 2 battery bank for the engine and normal boat use and will be using the solar system for other things


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## Maine Sail (Jan 6, 2003)

PCP said:


> Thanks for the link
> 
> But even after reading your comments I still think that AGM makes sense to my case.
> 
> ...


The bolded part makes little sense...? That is a VERY SMALL bank if planning to be on the hook for extended periods and running refrigeration. 400Ah and up are pretty standard bank sizes these days especially if running DC refrigeration. A 400 Ah bank of wets will take about what your alt can produce so no acceptance gain with AGM.

The problem with alternators is that all batteries, wet, gel AGM but not LiIon begin drastically limiting "accepted current" at about 80% state of charge. So the area you're concentrating on is between 50% SOC and 80-85% SOC. Beyond that it makes little sense to run the engine for charging. Your 120 amp alt will likely supply about 85-90A when hot....

"Usable" battery capacity gets really small really fast...










You need CURRENT to be able to take advantage of the high acceptance rates of AGM and you really don't have it... With a small bank you could see slightly faster charging between 50% SOC and 80% SOC, but then a small bank is not very suitable for your cruising needs with two refrigerators. You really need a battery monitor and to know what you use in Ah's per day.


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## chef2sail (Nov 27, 2007)

360 ah means only 180 usable and if recharging on the hook without engine hard to get past the 85% part as you will also continue to use.

I would look at getting at least 4- 6 volt lifelines. Thats 440 or 480 depending on the ones you buy. The footprint space of the 4 6 volt will take up the room of less than 3 group 31. 3 group 31 is about 330 ah. Also you do not need battery boxes for the AGM just have to secure them although i did have the space for battery boxes. If you can get 6 in the space. I made dummies out of cardboard of the batteries and fit them into the compartment uinder my rear quarter berth to see the proper way to get them to fit. 

Lastly I would make an electrical diet to see what you usage is in an average day. That should help you figure out how many ah you will need for what you want to do. Our average ah/ day is about 80-90, 40 of which on a hot summer ( 90+) day is refrigeration. We have shower pumps, fans, labtop,as well as a C-80 chartplotter and ST-60 instruments and had gone to all LED lights...most Alpenglow.

Good luck on your choices. These batteries will last more than 4 yaers if you take care of them properly during charging and make sure you desulfate them correctly.

Dave


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## centaursailor (Nov 7, 2010)

I,m having to replace my 10 year old starter battery, won,t hold a charge, so understand I would be wise to replace the leisure at the same time. 
Have a small AGM that runs my electric outboard. Holds the charge well and charges up quickly but going up in size to a pair of 100+ Ah is expensive.
I,m thinking of a like for like replacement as I think 10 years of reliable use is hard to beat.


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## HMoll (Sep 18, 2007)

That is super useful feedback from Maine Sail. I will go back to it and read slowly, comments & links. My study of the situation is not as technical.

Here's the backround: J/35, weekend cruiser, once a month if lucky, boat in dock, two kids & wife, Puerto Rico. It rains very often during evenings in the Caribbean (short & heavy), so I got sick of getting up to close hatches and then back up to open. Then came genset, 2.5K Mase, to run A/C. It "killed" the sailboat "feel" for sleeping, no matter the soundproofing & vibration damping (which was more important but I was limited in height). Genset out, and starter studying batteries further.

Decision: high accceptance rate, "virtually no gas emissions" (Deka-WM), putting high loads on them, and deep cycles (70% discharge). I upgraded alternator to a *Balmar 70A*, with programmable regulator.

Ok, about the A/C, I use it at night only, so it maintains a nice ambient temperature, not a refrigerator, like some of my boating friends. It's a Cruisair 10,000BTU/h, with a soft starter, which reduces load peaks. 3000W Gopower Inverter, and that's the system. I've run my A/C for 12h, very much over my calculations, but that depends a lot on the temperature difference you set (ext/int). Same story with your refrigeration, Paulo, tem and use (open/close). If you have two ref systems, have one to store unopened stuff and open it the least.

Custom made a SS crate for the new bank, on top of keel. My boat is a bit weight/balance sensitive, so that's a big plus. Need more experience on this, but I'm very excited. No dollar savings, just being a systems geek and sinking money, but this hobby/lifestyle doesn't make economical sense since the day you consider to buy a boat. I'll admit wasting some more than usual, but I also learn in the process.

Warnings, this is just as costly as a generator, but I think it's the future, especially in under 40' boats. Why hasn't the inverter-type technology of A/C gone marine yet? That will change the world of onboard power requirements. Next thread topic, Paulo?

Here's a picture of the bank. Made a custom cabinet/table over it, not pictured. Seventh batery is aft port, opposite to starting battery. Have a Link 2000 monitor but have yet to learn how to program it correctly.


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## Paul_L (Sep 16, 2004)

PCP said:


> You have them or work with them and that statment results from personal experience or is just your opinion?
> 
> Regards
> 
> Paulo


I'm a full time cruiser and am on my second set of AGMs. The house bank is 420ah with an Ample 100 amp alternator plus 320watts solar. The first AGMs failed in 1 year with crap for manufacturer support. The second set are Victron's, 2 years old now and working very well.


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## Maine Sail (Jan 6, 2003)

HMoll said:


> Decision: high accceptance rate, "virtually no gas emissions" (Deka-WM), putting high loads on them, and deep cycles (70% discharge). I upgraded alternator to a *Balmar 70A*, with programmable regulator.


With that alternator you are not even coming close to taking advantage of the acceptance benefit. The same bank it Wet Cell would take well over twice what you can effectively deliver. Deka recommends cycling the batteries to 50%...



HMoll said:


> Ok, about the A/C, I use it at night only, so it maintains a nice ambient temperature, not a refrigerator, like some of my boating friends. It's a Cruisair 10,000BTU/h, with a soft starter, which reduces load peaks. 3000W Gopower Inverter, and that's the system. I've run my A/C for 12h, very much over my calculations, but that depends a lot on the temperature difference you set (ext/int). Same story with your refrigeration, Paulo, tem and use (open/close). If you have two ref systems, have one to store unopened stuff and open it the least.
> 
> Custom made a SS crate for the new bank, on top of keel. My boat is a bit weight/balance sensitive, so that's a big plus. Need more experience on this, but I'm very excited. No dollar savings, just being a systems geek and sinking money, but this hobby/lifestyle doesn't make economical sense since the day you consider to buy a boat. I'll admit wasting some more than usual, but I also learn in the process.
> 
> ...


Your bank can become "imbalanced" if you keep it wired like that..










Yours looks wired like this:


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## PCP (Dec 1, 2004)

Maine Sail said:


> The bolded part makes little sense...? That is a VERY SMALL bank if planning to be on the hook for extended periods and running refrigeration. 400Ah and up are pretty standard bank sizes these days especially if running DC refrigeration. A 400 Ah bank of wets will take about what your alt can produce so no acceptance gain with AGM.
> 
> The problem with alternators is that all batteries, wet, gel AGM but not LiIon begin drastically limiting "accepted current" at about 80% state of charge. So the area you're concentrating on is between 50% SOC and 80-85% SOC. Beyond that it makes little sense to run the engine for charging. Your 120 amp alt will likely supply about 85-90A when hot....
> 
> ...


Thanks a lot!

But regarding this, that is central to me:

*You need CURRENT to be able to take advantage of the high acceptance rates of AGM and you really don't have it... With a small bank you could see slightly faster charging between 50% SOC and 80% SOC...A 400 Ah bank of wets will take about what your alt can produce so no acceptance gain with AGM.*

My calculations show that I will have a big difference is recharging times. Maybe I mess it up. Do you mind to check these calculations? I have used for the calculations data posted by you here:

Battery Acceptance Observations - SailboatOwners.com

According from what I have understood from your article, wet cell batteries can accept 20% charging when they are almost empty but regarding the charging that matters most, between 50% and 85% they can only accept between 13% and 7.5%.

*SOC______Accepted Current______% of 20 Hour Rating
53% ____________15.3 amps___________________12.8% Acceptance
83% ____________9.1 amps____________________7.5% Acceptance
86% ____________7.1 amps____________________5.9% Acceptance
88% ____________5.2 amps____________________4.9% Acceptance
90% ____________4.6 amps____________________3.8% Acceptance
93%_____________3.8 amps____________________3.1% Acceptance
*

Considering an average 11,5% charging acceptance and considering a 360Ah bank the the batteries are accepting 41 Amp.

What I have read about AMG batteries talk about an acceptance two or three times superior. If we consider 3 times, the acceptance will be 124 Amp for that bank, that would be superior of what the 120Amp alternator can provide when hot (about 90) but all those 90amp will be sucked by the batteries and that would give a charging time a bit less than half the time than with wet cell batteries.

If we consider that the AMG can accept only 2 times the charge of wet cells, than they are accepting 81 Amp and the 120Amp alternator is good for that and it is still half the charging time of wet cell batteries.

Mainsail, You are the one that now about this, I am learning and I don't want to make a point out of this, just trying to understand, so please if there is something wrong with these calculations please tell me.

Regarding this:

*That is a VERY SMALL bank if planning to be on the hook for extended periods and running refrigeration. 400Ah and up are pretty standard bank sizes these days especially if running DC refrigeration...You really need a battery monitor and to know what you use in Ah's per day.*

For what I have seeing on this thread I guess you guys are less frugal than the average European in what regards life style aboard and electric consumption on small boats.

On my last boat (a 36ft) I had a 240Ah home battery bank (the boat come standard with 120Ah and 240Ah was with an extra battery) and two small engine alternators to charge it. I used a Link 20 to control the batteries.

With that I could stay on anchor for a week and when I went to the marina was more for water than for charging. Normally I moved around so in most cases I was doing an hour with the engine so if that was the case I did not need to run more the engine for charging. If I staid on the same spot I would need to run the engine for an hour.

Of course this implied a very restricted use of energy: The refrigerator was turned off at night and after 21.00 and it was out of limits to open it. We open it only when it has indispensable, we made a very careful use of lighting, used independent solar charged lighting for most of uses including dinning outside and reading at night. The position light was also solar powered.

That scheme had worked for 7 years and I never changed the batteries, so it was sustainable. I cruised and lived on the boat for 45 days out of the marina in the summer and out of that I used the boat only for weekend sailing, returning to the marina.

On this boat, yes, I have two fridges but If I can only use one on batteries it will be alright for me. The insulation on this fridge is much better than on the other boat, this boat had led lights and a 360Ah bank (more 120Ah) than on the other boat. If I can charge the batteries two times faster, I am quite sure the 360Ah bank will suit my needs. I will be cruising for more time on the summer, out of marinas, maybe 3 to 4 months.

Sure I would prefer to have a 450Ah bank, and it is possible that I could manage the space for that but the max alternator that engine has is a 120Amp and the 450Ah bank would need a bigger alternator.

The alternator that the engine has actually is a 80 amp one. I am going to change to a 120 amp, so I am going to buy an alternator anyway. *Do you know if any American or European brand, for that matter, has bigger alternators that fit on the Lombardini LDW 1404M (40hp)?*

Regards

Paulo

...


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## PBzeer (Nov 11, 2002)

I have 3 Group 31 West Marine branded AGM's that I bought in '06. 70 amp alternator w/ext regulator, wind generator, and a Honda 2000 that I use to run the battery charger on the hook. I'll be replacing my AGMs this spring. Cost depends on where and how you buy them.


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## Paul_L (Sep 16, 2004)

PCP said:


> ..According from what I have understood from your article, wet cell batteries can accept 20% charging when they are almost empty but regarding the charging that matters most, between 50% and 85% they can only accept between 13% and 7.5%.
> 
> ...


You also need to consider the time to charge the 85 to 100%. If you fail to do this periodically on AGMs then the batteries will have a short life. Since you are a light user of your power, you may find that you are effectively using the 70% to 100% range on the batteries. In this case the AGMs will recharge slightly faster than standard wet cells, but not significantly. If you use the range 55 to 85%, and don't go to 100%, then AGMs will recharge faster if you have the charging amps available, but they will not be happy batteries. How often is 'periodically' to 100%. That's a tough call -- maybe twice a week???


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## PCP (Dec 1, 2004)

HMoll said:


> That is super useful feedback from Maine Sail. I will go back to it and read slowly, comments & links. My study of the situation is not as technical.
> 
> Here's the backround: J/35, weekend cruiser, once a month if lucky, boat in dock, two kids & wife, Puerto Rico. It rains very often during evenings in the Caribbean (short & heavy), so I got sick of getting up to close hatches and then back up to open. Then came genset, 2.5K Mase, to run A/C. It "killed" the sailboat "feel" for sleeping, no matter the soundproofing & vibration damping (which was more important but I was limited in height). Genset out, and starter studying batteries further.
> 
> ...


That's a big bank What is the capacity?

How can you charge it with a 70amp alternator?

It would not make sense if you used a small powerful DC generator to have them charged? That way you would have no noise, except one our a day will you charge them.

Regards

Paulo


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## PCP (Dec 1, 2004)

Paul_L said:


> You also need to consider the time to charge the 85 to 100%. If you fail to do this periodically on AGMs then the batteries will have a short life. Since you are a light user of your power, you may find that you are effectively using the 70% to 100% range on the batteries. In this case the AGMs will recharge slightly faster than standard wet cells, but not significantly. If you use the range 55 to 85%, and don't go to 100%, then AGMs will recharge faster if you have the charging amps available, but they will not be happy batteries. How often is 'periodically' to 100%. That's a tough call -- maybe twice a week???


Yes, that seems important, I mean to know: *How often is 'periodically' to 100%. That's a tough call -- maybe twice a week???*

I would like to know more about that. I was hoping that once in 15 days would be enough. Does anybody knows more about this, I mean the max time they should be charged to 100% to not shorten their live significantly?

Regards

Paulo


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## PCP (Dec 1, 2004)

chef2sail said:


> I have 6 -6 volt Lifeline AGM. 720 ah. ...
> 
> My advantages.-
> 6 volts easier to pick up than 8D.
> ...


Dave, I did not reply because I don't know enough to understand the implications of running on 6 Volt batteries all boat systems that run at 12V.

You have 720 Ah at 6 Volts, that corresponds to 360Ah at 12V? Where it is made the conversion (6 to 12V)? There re losses on that conversion?

The main advantage is space?

I have a nice battery box right over the keel at the boat center:










The boat weights are carefully balanced and I don't want to change their place.

Eventually they can be higher (bigger) and have more capacity but I don't think I have an alternator with power for more than 360Ah on the home bank. I guess that what I really want to know is if the AGM with that alternator (120Amp) will charge in about half time (considering charging time of wet batteries 50% to 85%) and how many times in a month I will have to charge them to 100% for not shorten much their life span.

Regards

Paulo


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## chef2sail (Nov 27, 2007)

Paulo,

2 -6 volt batteries placed in series= 1 12 volt battery...then placed in parrallel. Each seried pair of batteries is 240 ah. 3 groups of seried batteries =720 ah of 12 volt power.

If you have 360 ah of batteries- charging at 120 amp alternator ( thats what I have and Maine sail recommends electromax alternators vs Balmar) , and the 360 ah batteries dont discharge below 1/2 or 180 ah and you want to get to 85% by engine charge you have approx 150 you need to get in which is about 1.25 hours of engine time to get 180 ah.


If you had 720 ah of batteries you could go twice as long without charging as you need to charge 360 ah in. Alsdoo a passive charger like you are planning on will help this too.


This way you do not have to be a frugal with your energy like turning of refrigeration etc. We can generally go 5-6 days without using the engine.

Dave


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## Maine Sail (Jan 6, 2003)

PCP said:


> Thanks a lot!
> 
> But regarding this, that is central to me:
> 
> ...


What I should clarify in that article is that the charger was a 15A charger. Reading it now it does appear as the batteries only accepted 12.8% but they were taking all the charger could give until about 80% SOC. The batteries took the full current of the charger until they hit about 80% SOC then began taking less than the 15.3A the charger was capable of. I was concentrating on the acceptance above 80% SOC and made it appear that the battery was only capable of taking 15.3A but it was the charger that was only capable of delivering 15.3A.

Those were also "used" batteries typical of what one might find on a boat with a poor charging system. They were slightly sulfated and had never been equalized which can mean they accept less current than they normally would. 20-25% acceptance for wets, in bulk, it what you can expect provided everything is in good working order.



PCP said:


> Considering an average 11,5% charging acceptance and considering a 360Ah bank the the batteries are accepting 41 Amp.


Again, my bad, and I apologize for not writing that more carefully. Wets should take approx 25% of "C" when in good condition. I've seen some "dual purpose" thin plate wets take as much as 27-30%. AGM's take about 40% + but usually tend to settle out at around 35-40% until you hit about 80% SOC.



PCP said:


> What I have read about AMG batteries talk about an acceptance two or three times superior.


I have seen a brand new 100Ah AGM take 85A for a decent amount of time but this is not the "norm" and that battery was brand new. A new wet would take about 25%.



PCP said:


> If we consider 3 times, the acceptance will be 124 Amp for that bank, that would be superior of what the 120Amp alternator can provide when hot (about 90) but all those 90amp will be sucked by the batteries and that would give a charging time a bit less than half the time than with wet cell batteries.


If you consider a wet bank taking 25% and an AGM bank taking roughly 40%, which is about the average I see in real use on boats, then the numbers change. The acceptance rates on both types of batteries will drop as the bank becomes sulfated. Some AGM batteries can not be "condition charged" or equalized, wets can. 25% of 360Ah is 90A, 40% of 360Ah is more than your alt can likely deliver unless cold..



PCP said:


> On this boat, yes, I have two fridges but If I can only use one on batteries it will be alright for me. The insulation on this fridge is much better than on the other boat, this boat had led lights and a 360Ah bank (more 120Ah) than on the other boat. If I can charge the batteries two times faster, I am quite sure the 360Ah bank will suit my needs. I will be cruising for more time on the summer, out of marinas, maybe 3 to 4 months.


I had to base my statements on what you wrote and that included "two refrigerators".. If you're running just one and turning it off at night and you've converted to LED a 360Ah bank will be fine.

We run a 375 Ah bank, all LED but have engine driven refrigeration and a 50A dumb regulated alternator. My friends, the previous owners, did a 5 year 100% live aboard on-the-hook wold cruise and used the same alternator and a single 80W solar panel. They used Wal*Mart wet cells and they were still working when I bought the boat at year six.



PCP said:


> Sure I would prefer to have a 450Ah bank, and it is possible that I could manage the space for that but the max alternator that engine has is a 120Amp and the 450Ah bank would need a bigger alternator.


A larger bank will have shallower discharges which can lead to longer life. Most cruisers run their banks between 50% SOC and 80-85% SOC. On a 450Ah bank that means you need to replace about 135Ah to get from 50% to 80%. To do this in an hour you'd need a 160 - 175A alt (140+ A hot rated) and the belts to back it up. With wets they could take about 100A or 100Ah per hour of run time. With AGM you could put it all back in 1 hour but only IF you have the ability to do so. The max you can run on a single 1/2" belt is about 100A. You'd need a seprentine kit or custom dual pulleys to do more.

With a 360Ah bank it would take 108 Ah's to re-charge from 50% to 80% in an hour. A 360Ah bank of wets should take around 90A in bulk so you;re 18Ah shy. With AGM you could do it in an hour but is all the expense, belts, alternator & bank worth the difference? It may be..



PCP said:


> The alternator that the engine has actually is a 80 amp one. I am going to change to a 120 amp, so I am going to buy an alternator anyway. *Do you know if any American or European brand, for that matter, has bigger alternators that fit on the Lombardini LDW 1404M (40hp)?*
> 
> Regards
> 
> ...


Problem is your belt. If spending the premium on AGM for a 360Ah bank, that can take about 145A of current in bulk, a 175 - 200A alt is the only way to really maximize your investment if your motor can handle it.. A 120A alt is well sized to a 360Ah bank of wets but undersized to maximize the "acceptance" of AGM.....


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## Maine Sail (Jan 6, 2003)

PCP said:


> Dave, I did not reply because I don't know enough to understand the implications of running on 6 Volt batteries all boat systems that run at 12V.
> 
> You have 720 Ah at 6 Volts, that corresponds to 360Ah at 12V? Where it is made the conversion (6 to 12V)? There re losses on that conversion?
> 
> ...


Paulo,

If you can try to give a little room between the AGM batteries. They run hotter when charging than wets and heat kills batteries. You'll also want to move your POS or NEG cable to the opposite end of the bank to keep the banks "balanced" this forces all the loads and currents to be more equally run "through" the bank not off the end battery in the string which the way it is wired sees the most use...

If I put my analyzer on your bank I can nearly gurantee the battery closest to the starting battery is in the worst shape and the one at the opposite end is in the best shape...


----------



## Maine Sail (Jan 6, 2003)

PCP said:


> Yes, that seems important, I mean to know: *How often is 'periodically' to 100%. That's a tough call -- maybe twice a week???*
> 
> I would like to know more about that. I was hoping that once in 15 days would be enough. Does anybody knows more about this, I mean the max time they should be charged to 100% to not shorten their live significantly?
> 
> ...


This is a stetement from Justin G. at Lifeline Battery regarding expected life cycles for Lifeline AGM.

*"Put broadly, there are four ways that will yield different lifetimes based on daily 50% deep cycles:

1- Fully charge after each discharge. Estimated life: 6-9 Years.

2- Fully Recharge at least once a week and equalize once a month. Estimated life: 4-6 Years.

3- Only recharge to 85% and equalize once a month. Estimated life: 2-4 years.

4- Only charge to 85% and never equalize. Estimated life: 1 year."*

The thing I really LIKE about Lifeline is that they are HONEST.....


----------



## Paul_L (Sep 16, 2004)

And they seem to be the only AGM manufacturer who wants monthly equalization. Something that isn't too likely on a cruising boat.


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## PCP (Dec 1, 2004)

Maine Sail said:


> What I should clarify in that article is that the charger was a 15A charger. Reading it now it does appear as the batteries only accepted 12.8% but they were taking all the charger could give until about 80% SOC. The batteries took the full current of the charger until they hit about 80% SOC then began taking less than the 15.3A the charger was capable of. I was concentrating on the acceptance above 80% SOC and made it appear that the battery was only capable of taking 15.3A but it was the charger that was only capable of delivering 15.3A.
> 
> Those were also "used" batteries typical of what one might find on a boat with a poor charging system. They were slightly sulfated and had never been equalized which can mean they accept less current than they normally would. 20-25% acceptance for wets, in bulk, it what you can expect provided everything is in good working order.
> 
> ...


Thank you very much! Crystal clear and food for thought.

I will have to reconsider everything. I have learned a lot

One last question, how much is typically the charge rate for Gel batteries?

Regards

Paulo


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## Maine Sail (Jan 6, 2003)

PCP said:


> Thank you very much! Crystal clear and food for thought.
> 
> I will have to reconsider everything. I have learned a lot
> 
> ...


Also about 35-40% but properly charged GELS seemingly last forever. Lifeline batteries consistently take more current than other AGM's I see but they are also more costly. Of course they are also the only ones I know of that can be equalized so that probably brings life cycle costs down...


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## Maine Sail (Jan 6, 2003)

HMoll said:


> Decision: high accceptance rate, "virtually no gas emissions" (Deka-WM), putting high loads on them, and deep cycles (70% discharge). I upgraded alternator to a *Balmar 70A*, with programmable regulator.


The problem is, with your bank, you do not have the ability to take advantage of the "acceptance" of those Deka AGM batteries.. If we figure 40% acceptance, that bank, which appears to be Deka group 31's at 105Ah each, can take about 250A of charge current.

You have a 70A Balmar alt, (perhaps a 6 series) which when hot at about 2500 alt RPM can deliver about 60A. Of course when the alternator gets hot the regulator reduces the output even further to prevent the alt from burning itself up. Supplying a bank that can take 250A with an alternator only capable of 60A makes it get VERY hot. I would hope, for the sake of the alternator, you have an alt temp sensor connected..!!

So, the net benefit of AGM's for the high acceptance, for your application, is currently zero...



HMoll said:


> Ok, about the A/C, I use it at night only, so it maintains a nice ambient temperature, not a refrigerator, like some of my boating friends. It's a Cruisair 10,000BTU/h, with a soft starter, which reduces load peaks. 3000W Gopower Inverter, and that's the system. I've run my A/C for 12h, very much over my calculations, but that depends a lot on the temperature difference you set (ext/int). Same story with your refrigeration, Paulo, tem and use (open/close). If you have two ref systems, have one to store unopened stuff and open it the least.
> 
> Warnings, this is just as costly as a generator, but I think it's the future, especially in under 40' boats. Why hasn't the inverter-type technology of A/C gone marine yet? That will change the world of onboard power requirements. Next thread topic, Paulo?


Unfortunately until LiIon batteries become more prevalant this will not be the case. Why?

Your calculations have probably not taken into account the Peukert effect.

Lets guess your AC draws 7A at 120V this means that at 12V it is drawing 70A but we are now running it through an inverter with about an 80% efficiency.

840 Watts / 12V = 70A X 1.2 (80% efficiency) = 84A

So now we look at a 630Ah bank and calculate Peukert. With a Peukert value of 1.2 (based on best recollection of Deka AGM) and we now have a bank that only has 517 Ah as opposed to the 630 Ah most base the calculation on.

If were doing the math we just lost an ENTIRE batteries worth of Ah capacity due to the high current load being applied by the AC via the inverter. The bank has just lost 113Ah to a pesky little calculation that most completely forget about when running inverters.

However the size of your bank is still the same so 315Ah is 50% discharged. If hitting them with 84A you now only have 202 Ah's before hitting the recommended 50% depth of discharge from a 100% state of charge. 202Ah / 84 gives you 2.4 hours of cumulative run time for your AC providing you are running nothing else IF starting from 100%...

If you're out cruising and only getting back to 80% your calculation gets a LOT worse and gives you well under 2 hours of AC run time.

That said to get from 50% to 80% with your alternator & bank requires 190 Ah's, plus charge inefficiency be replaced, or about 200-210Ah's..

200 Ah's / 60A takes a full 3.3 hours per day of engine run time just to move between 50% SOC and 80% SOC..

If you're going to 70% DOD as you mentioned, you need to replace 315 Ah's to get back to 80% SOC. This now takes 5.25 hours per day of motor run time just to go from 30% SOC to 80% SOC and this did not include charge inefficiency or the regulator cutting the alternator back because it got hot enough to boil eggs...

This is why running AC's on boats, with batteries, is not often done and won't become very popular until we can come up with a way to quickly replace the current and have batteries that have no Peukert effect like Li technology.

When batteries are hit with a load above their 20 hour Ah rating load they suffer Ah capacity loss. For a 630 Ah bank to get 630Ah delivered over 20 hours the load would be 31.5A.

630 Ah bank / 20 = 31.5A

105 Ah battery / 20 = 5.25A

Any load above 31.5A on this 630 Ah bank results in less total Ah's.... As batteries age and sulfate the Peukert value creeps up and all these calculations get worse....


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## HMoll (Sep 18, 2007)

Thanks, Maine Sail. Before going into this, I did an Excel worksheet. I do remember Peukert factor and had taken it into account. The bank is 735Ah (7th battery not in picture). I was afraid of a larger alternator due to my engine size (Yanmar 3GM 20hp), but I had not realized the heat issue having it work overtime. (I assumed these expensive Balmars were designed for that duty-yes, it's a 6-series). I did calculate 6 hrs recharge time, but would rather run engine during the day than a genset at night. Again, the longest stay in my boat is 4 days, and usually its just two nights (long weekend). The A/C is drawing 77A on cooling cycle and 7A on fan cycle (measured on the battery cable). Should I upsize alternator? I'd have to change pulley in that case. Running at idle, mine is putting 55A into the batteries. I have also done 4 hours running engine and A/C and it seems to balance out consumption (batteries remain at same exact voltage). Maybe consider some solar to make up for the deficiency? wind too? It seems renewables are insignificant when talking about these loads, but then again, it may add up? I will install alt. temp sensor at least. Thanks again, Hans.


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## deckofficer (Feb 18, 2012)

Boy, it is good so see knowledgeable folks on this forum. Reminding people of the Peukert effect, most aren't aware of the fact that the larger the wattage draw from a battery, the less the capacity over advertised a/hr rating. My next battery bank will be LiFePO4 and 48 volts for the inverter. I have used the Odyssey AGM batteries and couldn't be happier (except the cost). Lowest self discharge, highest surge amps per weight, no corrosion, accepts 3.0C instead of 0.1C of flooded, and much longer life than flooded.


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## Maine Sail (Jan 6, 2003)

deckofficer said:


> I have used the Odyssey AGM batteries and couldn't be happier (except the cost). Lowest self discharge, highest surge amps per weight, no corrosion, accepts 3.0C instead of 0.1C of flooded, *and much longer life than flooded.*


Just curious how long you've had your TPPL's? I have three customers with them but the oldest bank is at year three and will be getting an Electromaax serpentine kit and 160A alt this spring. According to the analyzers they are still doing okay. Not ready to jump in full swing as I got burned hard by AGM doing that. Still waiting on the longevity reports for TPPL in the marine space...

Would love to hear some TPPL success stories in the 6+ year range...


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## deckofficer (Feb 18, 2012)

I have a PC680 for a starting battery, ran it 17 years, and I pulled it and now it starts my garden tractor. I also have (4) PC680's in series on my "dinghy transportable" electric scooter and have 1680 miles on those batteries. That is over 500 charges from 50% DOD.


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## chef2sail (Nov 27, 2007)

Maine as always excellent information. I am going down today to put a small wood block between each of the batteries to allow heat removal space.

Glad you satyed here..


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## PCP (Dec 1, 2004)

HMoll said:


> Thanks, Maine Sail. Before going into this, I did an Excel worksheet. I do remember Peukert factor and had taken it into account. The bank is 735Ah (7th battery not in picture). I was afraid of a larger alternator due to my engine size (Yanmar 3GM 20hp), but I had not realized the heat issue having it work overtime. (I assumed these expensive Balmars were designed for that duty-yes, it's a 6-series). I did calculate 6 hrs recharge time, but would rather run engine during the day than a genset at night. Again, the longest stay in my boat is 4 days, and usually its just two nights (long weekend). The A/C is drawing 77A on cooling cycle and 7A on fan cycle (measured on the battery cable). Should I upsize alternator? I'd have to change pulley in that case. Running at idle, mine is putting 55A into the batteries. I have also done 4 hours running engine and A/C and it seems to balance out consumption (batteries remain at same exact voltage). Maybe consider some solar to make up for the deficiency? wind too? It seems renewables are insignificant when talking about these loads, but then again, it may add up? I will install alt. temp sensor at least. Thanks again, Hans.


As you have seen I am learning but I have made some research regarding my problem and particularly regarding size of alternator and the use of a generator so a question to you:

It seems that you have used an AC generator to run your Air conditioner and that means having the generator working most of the time and making a lot of noise. But there is another alternative, why don't you sell that generator and get one of these?:

D.C. Traveller | HFL

They are small light (72kg) and produce directly DC current via an integrated powerful alternator (140 Amp). This works not powering directly the Air Conditioner, but charging the batteries. If you run this baby and the engine at the same time you will get 210Amp on alternators and even considering losses with temperature they will be good for about 170 Amp charging power that is 3 times more than you have now. That would reduce the charging time of your batteries to about 2 hours, and that seems more reasonable to me.

There is also this one, but it seems heavier and bigger even if a lot more powerful. With this one you would charge your batteries in a bit more than an hour (using also your engine). this one looks more expensive and would be more adequate to your battery bank but not to the size of your boat.

Marine Micro-Cogen for recreational and commercial vessels

The other one is not expensive and I am sure is no bigger than the generator you have, probably smaller.

Hei Mainsail, please see if I am saying a lot of rubbish please

Regards

Paulo


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## HMoll (Sep 18, 2007)

Good info, Paulo, especially if my boat grows one day. One of the reasons I also eliminated the genset is that I felt the weight aft, although it is only 145#! The boat now feels very well balanced, and that is a priority too. After yesterday's advice, I'm considering adding 1. wind, 2. solar, and then a larger alternator (maybe 6-series 140A). Again, I'm mostly a weekender and for that, the actual setup is more than adequate, but I certainly don't want to cook my alternator. Excellent info on this thread though! I'll keep watching.


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## deckofficer (Feb 18, 2012)

The above is also my choice. Having a good quality, full sine wave inverter and an AC gen-set is redundant. The DC gen-sets are lighter, charge the bank much faster, and are not rpm dependent for frequency regulation.


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## HMoll (Sep 18, 2007)

I wonder if my Yanmar 3GM 20hp will crank a 95 series 165A. What is it 25A/hp? Anyone.....anyone.....MaineSail?


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## HMoll (Sep 18, 2007)

Mase 2.5, 2007, low hours, was saving it for future, now going cheap!!!!


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## deckofficer (Feb 18, 2012)

HMoll said:


> I wonder if my Yanmar 3GM 20hp will crank a 95 series 165A. What is it 25A/hp? Anyone.....anyone.....MaineSail?


25 X 15.2 = 380 watts / 746 = 1/2 hp.

165 X 15.2 = 2508 watts / 746 = 3.36 hp


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## PCP (Dec 1, 2004)

HMoll said:


> I wonder if my Yanmar 3GM 20hp will crank a 95 series 165A. What is it 25A/hp? Anyone.....anyone.....MaineSail?


I guess the problem is not if the engine can handle it but how much power is going to remain to drive the boat, specially in difficult situations. 20hp is not much for a 35ft boat....

Regards

Paulo


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## deckofficer (Feb 18, 2012)

Should be enough. He is only needing 15.2 volts for charging, and at the alternators full output of 165 amps, should only use about 3.5 hp. Now if he was charging my proposed 48 volt bank at the same 165 amp, that would only leave 6 hp for main propulsion, a bit on the low side for a 35' boat.

Besides, he can via the field, switch the alternator off should he need more power for propulsion.


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## chef2sail (Nov 27, 2007)

Check out electromaxx alternators vrs Balmar. Was recomended to me by Maine Sail. Have been very haoppy with it and a change to sepentine belt on GF30 Yanmar Plus temp sensor 

Dave


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## SimonV (Jul 6, 2006)

Maine Sail said:


> Also about 35-40% but properly charged GELS seemingly last forever. Lifeline batteries consistently take more current than other AGM's I see but they are also more costly. Of course they are also the only ones I know of that can be equalized so that probably brings life cycle costs down...


I have West Marine Gels that where new in 2005 they have been in constant use, lately I felt they were taking forever to reach full charge, so I had the local electrician come down and do a load test and check the charging systems. Well the bats passed with flying coulors, being as good as the day they were put in.....turned out the max charge volt had been changed ion the Battery monitor giving a false reading and not reaching the charge point as soon as it should. I expect to get another 3 or more years or more from the bank.

The marine electrician stated I had a good set up with solar, wind and 110amp alternator and never let the bank get below 11.9 volts. At this rate if I ever replace the bank it will be with Gels.


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## gershel (Feb 4, 2001)

I installed 4-6v gels from West Marine in Oct. 1997 and never looked back. They're still going strong, and talk about maintainance free, I sometimes forget they're even there.
Marc


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## PCP (Dec 1, 2004)

I have a question regarding this:

As Gel cells are sealed and cannot be re-filled with electrolyte, *controlling the rate of charge is very important or the battery will be ruined in short order. Furthermore, gel cells use slightly lower charging voltages than flooded cells and thus the set-points for charging equipment have to be adjusted*.

Battery Types: Flooded versus AGM and Gel

Gel batteries generally require a specific charge profile, and a gel specific or gel selectable or gel suitable charger is called for. *The peak charging voltage for Gel batteries is 14.1 or 14.4 volts, which is lower than a wet or AGM type battery needs for a full charge. Exceeding this voltage in a Gel battery can cause bubbles in the electrolyte gel, and permanent damage.*

Battery Charging Tutorial | ChargingChargers.com

Because boats come with normal wet cell batteries it is probable that the boat alternator and ac charger are maximized for them, delivering a charge superior of the allowed 14.4 volts, thous ruining gel batteries.

What is the simplest and more effective way to deal with this without changing the existing alternator?

Regards

Paulo


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## Maine Sail (Jan 6, 2003)

PCP said:


> I have a question regarding this:
> 
> As Gel cells are sealed and cannot be re-filled with electrolyte, *controlling the rate of charge is very important or the battery will be ruined in short order. Furthermore, gel cells use slightly lower charging voltages than flooded cells and thus the set-points for charging equipment have to be adjusted*.
> 
> ...


I've not come across a single gel brand that can safely be charged at 14.4V, but perhaps they exists. I do not use terms like "must" very often but you MUST NOT charge GEL batteries at a voltage higher than the manufacturer recommends, ever.

The electrolyte is a Jello like consistency and when you over charge, it bubbles, and the bubbles are permanent. This destroys the battery. GEL's are perhaps the easiest to ruin via poor charging but when proper charging practices are used they can also be some of the longest pasting.

Also just because a "charger" says GEL on it or it has a "GEL" setting it can mean SQUAT, unless it is from a HIGHLY REPUTABLE manufacturer.

The Schumacher charger in the video below ruined a customers very expensive set of GEL batteries on the GEL setting. Schumacher denied any wrong doing depsite me noting this charging behavior on THREE of these chargers.....

I would not suggest buying GELS and then spending $50.00 on a sub par charger, or charge them at anything higher than 14.1V, or manufacturers recommended absorption & float voltages & never equalize a GEL there are none I know of that can be equalized....

This "cheap" charger, with GEL setting, cost my customer $1400.00!!!!!!! Caveat emptor!!!







PCP said:


> What is the simplest and more effective way to deal with this without changing the existing alternator?


Probably installing a Sterling Power A2B or Alternator to Battery charger... Sterling Power A2B Charger


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## PCP (Dec 1, 2004)

Maine Sail said:


> ..
> 
> Probably installing a Sterling Power A2B or Alternator to Battery charger... Sterling Power A2B Charger


Thanks Mainsail. It seems that a charge regulator is indispensable for the alternator.

I had a look and it seems to me a "smart" device but looking at the image the current that reaches the battery is superior to 14.1V. That can be regulated?










I think I will have dificulty finding that in Europe. I have tried to look at regulators from good brands that sell here and this one from Matervolt seems that can do the job. Can you confirm that?

Alpha Pro 12 V | Mastervolt Marine

Regarding the AC battery charger I have a Mastervolt Chargemaster 12/70-3

http://www.mastervolt.com/marine/products/chargemaster-12v/chargemaster-12-70-3/

It seems that it can handle Gel batteries, but it needs some adjustment or it automatically compensates? Or is just bullsh*t and I need also a regulator?

Regards

Paulo


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## Minnewaska (Feb 21, 2010)

Curious. I don't have a gel batt, but do have a Wet Marine charger, with settings for wet, gel, agm. Would you consider it reputable for use on a gel? I'm suspicious........

Edit.....l. It's the 30a version of this.

http://www.westmarine.com/webapp/wc...0001&storeId=11151&productId=101816&langId=-1


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## PCP (Dec 1, 2004)

deckofficer said:


> Should be enough. He is only needing 15.2 volts for charging, and at the alternators full output of 165 amps, should only use about 3.5 hp. Now if he was charging my proposed 48 volt bank at the same 165 amp, that would only leave 6 hp for main propulsion, a bit on the low side for a 35' boat.
> 
> *Besides, he can via the field, switch the alternator off should he need more power for propulsion*.


That seems interesting but I have no idea of what you are talking about. Please, do you mind to explain how I can prevent the alternator from taking away power from the engine without physically disconnect the transmission rubber?

Regards

Paulo


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## BigMoe (Oct 24, 2006)

*AGM Batteries. Mine work great!*

Hello Fellow Sailors:

I have 8 AGM batteries onboard my 2009 Beneteau 49 sailboat. I have never had any problems at all. I keep the battery charger hooked up all winter and I'm on shore power most of the summer. No problems at all. I do have a generator onboard so if they ever fail I have some redundency.

Big Moe


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## PCP (Dec 1, 2004)

*Re: AGM Batteries. Mine work great!*



BigMoe said:


> Hello Fellow Sailors:
> 
> I have 8 AGM batteries onboard my 2009 Beneteau 49 sailboat. I have never had any problems at all. I keep the battery charger hooked up all winter and I'm on shore power most of the summer. No problems at all. I do have a generator onboard so if they ever fail I have some redundency.
> 
> Big Moe


Jesus Moe! With all those batteries, hooked up all winter and on shore power most of the time plus a generator as a back up, it would be really very strange if you had any problem

Regards

Paulo


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## Minnewaska (Feb 21, 2010)

While I'm pretty good at crimping a proper connector and have the right tools. I can safely run 12v and 110v wiring, when the purpose is basic. I can follow much of the technical analysis above, but it starts to glaze my eyes over. 

I can also effectively use a multi meter for voltage and continuity. I can measure resistance, but rarely know what is good or bad, only relative to before/after.

My question is, what do I need and how to I check the health of a battery or bank of batteries? Specifically AGMs. 

I usually just swap out start batts ever few years for piece of mind. House batts go when we start to feel like it won't run system as long as it used to.

I would love to be able to do this more scientifically. Promise to try to follow along without tuning out.


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## MedSailor (Mar 30, 2008)

Maine Sail said:


> This is a stetement from Justin G. at Lifeline Battery regarding expected life cycles for Lifeline AGM.
> 
> *"Put broadly, there are four ways that will yield different lifetimes based on daily 50% deep cycles:
> 
> ...


Maine,

Do you think the above statement is a fair assessment of how long wets would last or does this only apply to AGM?

MedSailor


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## PCP (Dec 1, 2004)

On the category of silly questions, I mean the ones that show that I know little about the subject, I have one:

Normally the capacity of the batteries is given in Ah. I know that a small 12V one (boat size) can go from 55Ah to 100 Ah.

But some like Optima present their capacity as (C20) rate Ah, that I suspect is not the same measure of other manufacturers that only put the capacity without any other reference.

I know that AGM batteries are normally rated on a 20 hour rate (like the Optima). The wet cell batteries, when nothing more is said are rated on a 100 hour rate or on a 20 hour rate?

Deep Cycle Battery FAQ

Lot's of questions on this thread...and not enough answers


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## Maine Sail (Jan 6, 2003)

MedSailor said:


> Maine,
> 
> Do you think the above statement is a fair assessment of how long wets would last or does this only apply to AGM?
> 
> MedSailor


No I don't find that wets have the issues that AGM's do if not charged back to 100%. I have a customer with a bank of inexpensive wet cell 6V batteries that this spring will be 9 years old. He's never had them above 85% during the sailing season and only has an alternator.

That statement is direct from Justin G. from Lifeline Battery and pertains specifically to Lifeline AGM batteries.


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## Maine Sail (Jan 6, 2003)

PCP said:


> On the category of silly questions, I mean the ones that show that I know little about the subject, I have one:
> 
> Normally the capacity of the batteries is given in Ah. I know that a small 12V one (boat size) can go from 55Ah to 100 Ah.
> 
> ...


Ah capacity for deep cycle batteries is almost always the 20 hour rating so when you see 115Ah it is most likely a 20 hour rating.


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## stevensuf (Feb 26, 2012)

one thing about agms is they waste much less energy while charging or discharging, flooded batteries can waste up to 20% in/out as heat Agms more like 4%, so when chargin you can easily knock off ten percent of the charging time, now if using a genny or engine this can be a big saving if living abroad, but if you are a casual or weekend user, floodeds or cheapo sealed units make much more sense.


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## mitiempo (Sep 19, 2008)

stevensuf said:


> one thing about agms is they waste much less energy while charging or discharging, flooded batteries can waste up to 20% in/out as heat Agms more like 4%, so when chargin you can easily knock off ten percent of the charging time, now if using a genny or engine this can be a big saving if living abroad, but if you are a casual or weekend user, floodeds or cheapo sealed units make much more sense.


Except that agm batteries like to be totally charged regularly and if only using an engine or gen the last 15% it will still take hours and hours. Flooded batteries are more tolerant and while they like a full charge it isn't life shortening as it is with agm's.

Agm batteries can be a good choice if a full charge can be accomplished often as with the weekend sailor who plugs in an AC charger often or the cruiser with solar or wind charging to top up the last 15%.


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## PCP (Dec 1, 2004)

mitiempo said:


> Except that agm batteries like to be totally charged regularly and if only using an engine or gen the last 15% it will still take hours and hours. Flooded batteries are more tolerant and while they like a full charge it isn't life shortening as it is with agm's.
> 
> Agm batteries can be a good choice if a full charge can be accomplished often as with the weekend sailor who plugs in an AC charger often or the cruiser with solar or wind charging to top up the last 15%.


For what I understood if you stay out of marinas, have a powerful alternator and a big Ah battery bank and go each week to a marina for charging the batteries, the AGM are perfect. If you do not go to the Marina but have a powerful Hydro-generator or a similarly powerful solar or wind system that permits to top them once a week, that's perfect too.

If you only go once in 15 days to a marina it would not be perfect but not also a disgrace and the batteries probably would last over 4 years.

The Gel batteries will also accept a bigger charge than the wet ones (not as bigger as the AGM ones) but will need a very controlled charging that implies an expensive regulator, otherwise they will be destroyed in no time.

Wet batteries can last longer are less demanding, but compared with a properly AGM/alternator set-up can take 3 times more time to recharge to 85% with the engine.

Regards

Paulo


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## PCP (Dec 1, 2004)

And one more question, with a special thanks to Mainsail that has a big patience and share is knowledge for free.

here I have the power of these alternators related with the alternator RPM:

http://www.balmar.net/PDF/SIX-SERIES-ALTERNATORS.pdf

How does the alternator RPM relates with the engine RPM? It is directly or is normally multiplied? By 2?


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## remetau (Jan 27, 2009)

mitiempo said:


> Except that agm batteries like to be totally charged regularly and if only using an engine or gen the last 15% it will still take hours and hours. Flooded batteries are more tolerant and while they like a full charge it isn't life shortening as it is with agm's.
> 
> Agm batteries can be a good choice if a full charge can be accomplished often as with the weekend sailor who plugs in an AC charger often or the cruiser with solar or wind charging to top up the last 15%.


That was my experience with AGMs. We didn't get them fully charged often enough and ended killing them. We have switched back to wet cells.


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## tdw (Oct 2, 2006)

Paulo,
Technically I'm really not knowledgeable enough to add much to this thread but most weekends when we get to the boat our solar panels have us at 100% though I have to say when living on board we still find it difficult to keep them fully charged with the fridge going all day unless we run the engine an hour or so. New blades on the wind generator may sort this out as they are supposedly more efficient and quieter than the old ones though as I mentioned earlier running the engine for hot water is a daily task as it is. The batteries themselves are not old enough (under three years) for me to comment on longevity.


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## eherlihy (Jan 2, 2007)

PCP said:


> And one more question, with a special thanks to Mainsail that has a big patience and share is knowledge for free.
> 
> here I have the power of these alternators related with the alternator RPM:
> 
> ...


Drive (crankshaft) pulley diameter / driven (alternator) pulley diameter * drive RPM = driven RPM


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## PCP (Dec 1, 2004)

eherlihy said:


> Drive (crankshaft) pulley diameter / driven (alternator) pulley diameter * drive RPM = driven RPM


That I know. Not really different from the transmission of my old race bike and I changed the transmission for each race. But I am 3000km way from the boat and it is difficult to look at the engine right now. I have an idea that on my previous boat the crankshaft pulley was bigger than the one on the alternator.

Someone know what is the typical relation between the two pulleys?

Regards

Paulo


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## tdw (Oct 2, 2006)

Paulo,
Looking at a pic of the engine in our girl the alternator pulley (original equip not the Balmar) is about half the diameter of the engine pulley.

I'll try and get you a pic.

Andrew










Does that help at all ?


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## PCP (Dec 1, 2004)

tdw said:


> Paulo,
> Looking at a pic of the engine in our girl the alternator pulley (original equip not the Balmar) is about half the diameter of the engine pulley.
> 
> I'll try and get you a pic.
> ...


Yes, thanks. It was what I seem to remember from mine. That means the RPM of the alternator should be about 2 times more the ones from the engine and looking at these graphics:
http://www.balmar.net/PDF/SIX-SERIES-ALTERNATORS.pdf
we could see that the performance is not the same with all alternators in what regards RPM and that it is helpful to know the performance of the one we have on the boat, as well as the precise relation between the RPM from the engine and the ones from the Alternator.

Assuming that the alternator runs two times faster than the engine we can see that on the 70 and 100amp alternators with 1000RPM on the engine the performance is already near the top and that with 1250 it is practically max performance. No need to run the engine harder than that.

But the more powerful alternators with120 and 150A need more RPM to go near its Max potential. The 120 amp needs 2000RPM to get close and at 1000RPM it makes about the same power as the one with 100 amp . With the one with 150 Amps is even worse: It makes at 1000RPM about as much as the one with 70 Amp and a lot worse than the one with 120Amp.

The one with 150Amp needs also 2000 RPM on the engine to come near its max performance and with 1250RPM the performance is very close to the 120Amp one.

So this begs for a question: What are the Revs you use to charge batteries? I normally use about 1200, 1300RPM. Over that the engine starts to make a lot more noise and at that rotation there is not really a difference between the alternator with 150 Amps and the one with 120Amp.

Bottom point, it seems very important to know that relation between the RPM of engine and alternator, not only to know the better speed for charging but also to choose the alternator.

I have to see about that in what regards mine

Regards

Paulo


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## tdw (Oct 2, 2006)

Paulo,
Interesting. To be honest I hadn't given that a great deal of thought but when running engine for hot water or charging I don't like going over about 1250rpm. If for some reason I need to give the batteries a good hit I'll pull up anchor and go for a spin around the block. With the current setup I've never needed to do that. 
You do raise an interesting point however though most battery charging done by engine tends to be when under way, at least it does in my case.
cheers
Andrew


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## peterhurcos (Mar 12, 2012)

They sell AGM batteries now at Sam's Club. $175 for a 55 AH battery, which I don't think is a particularly cheap price.


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## mitiempo (Sep 19, 2008)

PCP said:


> Wet batteries can last longer are less demanding, but compared with a properly AGM/alternator set-up can take 3 times more time to recharge to 85% with the engine.
> 
> Regards
> 
> Paulo


Paulo

With your planned arrangement that won't happen. Based on Maine Sail's measurements wet will accept 25%C in bulk vs agm's 40%C in bulk mode.
Faster - yes a bit if the alt is big enough. The larger the bank, assuming a large alt, the more you gain. 360 AH and the alt you will have, which Maine Sail thinks will max at 90 amps hot will not gain you very much.

Read post #28 by Maine Sail again for the full explanation.


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## PCP (Dec 1, 2004)

mitiempo said:


> Paulo
> 
> With your planned arrangement that won't happen. Based on Maine Sail's measurements wet will accept 25%C in bulk vs agm's 40%C in bulk mode.
> Faster - yes a bit if the alt is big enough. The larger the bank, assuming a large alt, the more you gain. 360 AH and the alt you will have, which Maine Sail thinks will max at 90 amps hot will not gain you very much.
> ...


Based on what mainsail has said and in a lot more information I would say that the wet will accept between 20 and 25%, the Gel 40% and the AGM is dificult to say, but surely 50% and over.

You don't know what will be my planned arrangement because I made a reset after hearing Main Sail. I am still thinking and I have to see the space and the batteries I can have (I have space for batteries with an unusual height). I am still looking at the market in Europe but I guess that I can have between 345Ah and 450Ah on the house bank plus a 100Ah for the engine.

To have that capacity I can only have it with AGM. I don't find wet batteries with that capacity/size.

I am trying to see if a Balmar 150A can be fitted on the boat. I have posted their information about the performance:

http://www.balmar.net/PDF/SIX-SERIES-ALTERNATORS.pdf

They say it goes over 140Amp even hot.

With that alternator and even considering the 345Ah home bank I will charge two times faster the AGM than the wet ones. Another advantage is the more flexibility in sizes (higher batteries) and more capacity for size of the AGM batteries.

I am still studding the "thing" so if someone was any suggestions to make they will be more than welcome.

Regards

Paulo


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## Maine Sail (Jan 6, 2003)

PCP said:


> With that alternator and even considering the 345Ah home bank I will charge two times faster the AGM than the wet ones. *Another advantage is the more flexibility in sizes (higher batteries) and more capacity for size of the AGM batteries.*
> 
> Paulo


AGM batteries usually have less Ah's per case size than do wets.. In all but some esoteric power gen / back up power AGM cases the wets and AGM's are very often avaible in the identical case sizes.

Please be sure you are comparing apples to apples in that you are comparing a 20 hour AH rating to a 20 hour Ah rating. You can't compare reserve minutes or reserve capacity to Ah capacity at the 20 hour rate though I see people do it and then ruin the bank....


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## PCP (Dec 1, 2004)

Maine Sail said:


> AGM batteries usually have less Ah's per case size than do wets.. In all but some esoteric power gen / back up power AGM cases the wets and AGM's are very often avaible in the identical case sizes.
> 
> Please be sure you are comparing apples to apples in that you are comparing a 20 hour AH rating to a 20 hour Ah rating. You can't compare reserve minutes or reserve capacity to Ah capacity at the 20 hour rate though I see people do it and then ruin the bank....


No, I am a fast learner I am using C20 Ah rating for all. I am limited to what I can find here. I can find Optima that have a low capacity but also Varta and Lifeline.

Varta is a main provider in Europe and on their line of premium batteries that they call professional for similar size the AGM have more Ah (c20): 115 to 90 or 105Ah.

http://www.varta-automotive.com/fileadmin/leisure/Neue_Produktlinien_2012/programm-en.jpg

VARTA PROFESSIONAL - VARTA Automotive

Lifeline has even a better capacity.They have the GPL-31XT that offers 125Ah for the same size.

The wets I can find with that size have only 100Ah. Varta is an exception offering 105Ah, but that is still far from 125Ah and that difference X 3 are more 60Ah.

I don't know the size of the battery box of my boat and I don't know if they fit, but just a bit wider the Lifeline has the GPL-30HT that offers 150A. It is higher but I don't have a problem with that. I don't know of any wet batteries that have a regular shape but are higher, like this one from Lifeline.

Lifeline Batteries - Marine & RV Deep Cycle Batteries

Of course, this is just what I have found but I don't think here I can find wets with the same capacity of the AGM ones. Maybe I am not looking at the right places. Any suggestion?

Regards

Paulo


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## Maine Sail (Jan 6, 2003)

PCP said:


> No, I am a fast learner I am using C20 Ah rating for all. I am limited to what I can find here. I can find Optima that have a low capacity but also Varta and Lifeline.
> 
> Varta is a main provider in Europe and on their line of premium batteries that they call professional for similar size the AGM have more Ah (c20): 115 to 90 or 105Ah.
> 
> ...


These are examples of group 31 wets we have access to over here.

*Trojan SCS-225* / Group 31 = 130Ah
*US Battery 31DCXC* / Group 31 = 130Ah

I would not put Johnson Controls batteries, such as the Varta line, in the same class with Lifeline, Odyssey, Northstar or other high quality AGM batteries.

And yes with a 345Ah bank and a 140A alternator you CAN take better advantage of AGM's acceptance..


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## PCP (Dec 1, 2004)

Maine Sail said:


> These are examples of group 31 wets we have access to over here.
> 
> *Trojan SCS-225* / Group 31 = 130Ah
> *US Battery 31DCXC* / Group 31 = 130Ah
> ...


Thanks. It is a 150A alternator, 140A is what they say it can produce hot (Balmar).

Nice to know that I am making some sense. I plan also to have an hydrogenerator that can produce 500 watts sailing and as I like to sail that should top the batteries, I mean after the additional charge with the engine.

Regards

Paulo


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## chef2sail (Nov 27, 2007)

Paulo,

Did you look at the Lifeline 6 Volt- GPL-4 CT? The "footprint is 4 of them equals about the space of 3 group 31 and you wind up with 440 ah at 20 hrs. WE have 6 of them and remembr they can be laid on their sides even. An extra 60 lbs gets you 70 more ah or another 2 days without charging for us. You will be a happy with either Lifeline as long as you equalize them. They have 1 year full and 5 year limited warrenties also.

To measure our battery compartment for space or fit I made cardboard shoe boxes in the size of the batterries and fitted them in the space before buying them to figure out space and the right configuration as they are too heavy to play around with..

Dave


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## PCP (Dec 1, 2004)

chef2sail said:


> Paulo,
> 
> Did you look at the Lifeline 6 Volt- GPL-4 CT? The "footprint is 4 of them equals about the space of 3 group 31 and you wind up with 440 ah at 20 hrs. WE have 6 of them and remembr they can be laid on their sides even. An extra 60 lbs gets you 70 more ah or another 2 days without charging for us. You will be a happy with either Lifeline as long as you equalize them. They have 1 year full and 5 year limited warrenties also.
> 
> ...


Yes, I have seen them and when I saw them I understood why you have chosen 6V batteries. The size makes them very versatile in what concerns storage. Basically I have to study the best way to put the Max capacity on that battery box.

The 6 volt batteries are not excluded. I have to see what the best arrangement is. However putting them on another place is out of question. Batteries are heavy and that box is over the keel at the boat center and I want to keep the weight there 

Regards

Paulo


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## Jgbrown (Mar 26, 2012)

What about lifepo4? Less fire risk than Li-on. Pings packs are pretty reasonable. 
24V is the lowest standard pack but he builds custom packs too. Well regarded in the e-bike community, he stands behind his work and builds solid and reliable packs.

Ping specs:

Leadtime: 7 days
It will take about 7 days for us to build and test this new battery pack for you.

Specifications:
Suitable Wattage of Motor: up to 800W rated motor, 600 Watt suggested
Applications: E-Bike, Electric Bike, E-Scooter, Electric Scooter
Voltage: 24 Volts
Capacity: 30 Amp Hours
Dimension: 300x105x150 mm / 11.9x4.1x5.9 inches
Weight: 7.50 kg / 16.5 lbs
Charging Voltage: 30 Volts
Charging Current: <10 Amps
Rated Discharging Amperage: 30 Amps
Max Continuous Discharging Amperage: 60 Amps
Maximum Discharging Current: 100 Amps
Discharging Cut-off Protection: 75 Amps
Lifecycle of the whole pack: >85% capacity after 1000 cycles. Lifecycle of single cell: >85% capacity after 1500 cycles, >70% capacity after 3000 cycles. (<1C discharge rate and <1C charge rate)









Or alternatively, Golden Motors (goldenmotors.ca) makes some good large batteries, they use large flat cells IIRC. They are typically 48V, but can also build custom packs as well.

Both in the standard car battery format(to fit exisiting systems) and in stainless rectangular columns(wires at top)
48V20AH and 30AH respectively

















Pricey but if you are short on space, or you need something that AGM can't do they might be a good option.


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