# Solar low wattage charging?



## rnuzzolo (Oct 16, 2013)

Is it safe to use a low wattage panel without and controller?

1.5 Watt Solar Battery Charger

Brand Thunderbolt Magnum Solar
Maximum Output 24 V, 1.5 Watt
Wattage (watts) 1.5
Accessories Included Cigarette lighter adapter and battery terminal clamps

I am on a mooring and just looking for something two keep my two deep cell batteries up.

Rich


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## night0wl (Mar 20, 2006)

Yes, low wattage/aperage trickle maintainers are fine. They wont ever charge your battery, but they'll hopefully maintain a full charge. Remember, your battery has a natural discharge rate too...all these small panels hope to do is keep up with that. With cheap-o panels, you want to look out for a blocking diode. If it doesn't have one, then at night, your solar panel suddenly will become a power sink and could drain your battery! 

If you're super paranoid, then get a quality charge controller...and a dump load...etc etc. But now you're talking big money to bring it all together.


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## rnuzzolo (Oct 16, 2013)

Thank you for the advice. I all I am really trying to offset is natural daily drain on the batteries.

Rich


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## Maine Sail (Jan 6, 2003)

rnuzzolo said:


> Is it safe to use a low wattage panel without and controller?
> 
> 1.5 Watt Solar Battery Charger
> 
> ...


For a 1.5W panel and "two" batteries you would not need a controller but what your buying is pretty much a waste of your hard earned money.

Problem is your alt will barely get the batts back to 80-85% and if on a mooring your batteries will simply begin to sulfate and die. Sulfation is like battery cancer.. Getting them back to 100% as often as possible extends life and is like radiation treatment for the sulfation/cancer....

Charge controllers are very inexpensive these days as are 10W-20W panels that may actually put some charge back into the banks rather than just barely keeping up with self discharge. If on a mooring you don't just want to "maintain" the charge you need to replenish the used capacity.

There is no need for a "dump zone" with a solar panel and controller. Stick with an in-expensive PWM type controller and a 10+ watt panel and you will be fine.. The Morningstar SG4 is a good little PWM controller (not a shunt controller) and they can be had for about $30.00.....


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## Chas H (Sep 6, 2013)

Rich -
I use a Coleman 18 watt (max. rating - under optimum conditions) solar panel with a controller. The current rating is 1.2 Amps @ 15Volts. I have no other charging system.
A warning in the users manual states: Use a charge controller for wattages 15 and above.
- CH


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## JimsCAL (May 23, 2007)

Some good advice from Mainesail above. A 1.5 watt panel is a waste of money and effort. A decent 10-20 watt panel a basic PWM controller is about $100 or so and will do a good job at keeping the batteries topped off.


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## newhaul (Feb 19, 2010)

Harbor freight has a cheap 15 watt panel that comes with charge controler for around 50 bucks not the best but should do what you want to do on the cheap


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## christian.hess (Sep 18, 2013)

to repeat the good advice already stated there are some things worth hard earned money

cheap solar panels found at westmarine and the sort that are unregulated are only ok to use if you are on the boat as a liveaboard or cruiser...where you can constantly check...the reason I say this is that even a very small 5-10watt panel that is unregulated and you have no constant or cyclic loads like a bilge pump or anchor light, even this small wattage panel with unregulated voltage up to 22 volts or so WILL fry your battery...new even more.

take the time like mainsail says and buy a nice controller pwm...$25-40 and install your panel correctly nowadays you can find 50 watt panels that wil keep 2-3 bank systems completely charged and ready to use...for less than $100..

I envy you guys up in the states that have access to so many retail and internet options...

cheers


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