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solar maintenance charging batteries

hdlEric

Member III
So I want to use solar panels to maintain the charge on my batteries during the winter, and keep them on the boat. They are AGM; group 31; dual purpose batteries.

The problem is, I cannot figure out what I need and how to hook it up.

I have a 25 watt panel, with a regulator. Will that be enough to maintain a charge on both batteries?
How do I hook it up; directly to the batteries? Do I eliminate the selector switch?

As you can tell, I am not to savy on this, so speaking basic how to do it language would be appreciated.

thanks so much!!!
 

Frank Langer

1984 Ericson 30+, Nanaimo, BC
As I read your post, I'm not clear on whether you are doing a temporary installation just for the winter, perhaps while your boat is in storage, or if this is a longer term use for in the summer as well. AGM batteries hold their voltage much better than most other types of batteries, so unless someone more expert than me suggests otherwise, I would think your solar panel would be sufficient. Some of the older panels didn't work well if there was a shadow across any part of the panel, but newer ones seem to be overcoming that somewhat. Either way, placement of the solar panels to maximize sunlight would be good, though they also need to be out of the way if you're using them year round.
With a regulator, I would think they can be attached directly at the battery terminals - - I did that years ago on a smaller boat with no problems, but others with more electrical expertise may have a better idea.
Frank
 

Dave N

Member III
If this is a storage only install, aim the panel south and tilt it to reduce snow accumulation and enhance performance as the sun angle over the winter is very low. Shadows dramatically reduce effectiveness so position accordingly. Charge controllers are great, but with 2 group 31s and a 25 watt panel it would not be necessary. If you have a charge controller, the panel would first be connected to It and then the controller to the batteries. You can connect them directly to the batteries without the charge controller.
 

Maine Sail

Member III
So I want to use solar panels to maintain the charge on my batteries during the winter, and keep them on the boat. They are AGM; group 31; dual purpose batteries.

The problem is, I cannot figure out what I need and how to hook it up.

I have a 25 watt panel, with a regulator. Will that be enough to maintain a charge on both batteries?
How do I hook it up; directly to the batteries? Do I eliminate the selector switch?

As you can tell, I am not to savy on this, so speaking basic how to do it language would be appreciated.

thanks so much!!!

The answer here is simple..

#1 In the fall charge to 100% SOC

#2 Fully disconnect the batteries from the vessel and each other (either positive or negatives your choice)

#3 Reconnect in the spring...

There is no need for solar if the batteries are stored properly. AGM batteries have a very low self discharge rate and all batteries discharge significantly slower in cold weather, even flooded.

https://marinehowto.com/winter-battery-storage-self-discharge-characteristics/
 

David Grimm

E38-200
I just put the battery tender solar panle on mine. Seems pretty well made with led indicator. Just a tic over 100 bucks. You may want to buy the 12 foot extension cables as well. The cord on the panel is only about 6 feet.
 

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