benny23 avatar image
benny23 asked

Solar Blankets and Charging Input for battery.

So recently I had an issue with my 4A charger for my deep cycle battery and found out that I’ve been using an underpowered charger for my 100ah AGM.
Ive purchased an ip65 15A from now on. As I’ve been informed that I should be charging my battery at 10% of the capacity of the battery. This raises another question for me.
Can someone tell me why it’s generally perceived as acceptable to use 200-250w solar panels for charging AGM Batteries, even though most of those panels would struggle to output 10A let alone 10% of a larger battery?

battery chargingSolar Panel
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Jesse avatar image Jesse commented ·
Hard to find good science for this issue. Personally I think if you can make sure your battery spends an our two every few weeks at the proper absorption voltage then it'll be fine, more than that is only minimally helpful. Just as important then is to make sure it is kept cool etc to ensure long life.
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benny23 avatar image benny23 Jesse commented ·
I wondered why the guys at the two battery shops I went to were kind of dodging my question. They didn’t have an answer would be my guess, they kept referring back to it being fine to float your battery with a solar panel even though that’s clearly not what I was asking.

Ah well, new charger, it’ll get put on that every second night so no dramas from here on hopefully.

thanks for your reply!

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1 Answer
Mike Dorsett avatar image
Mike Dorsett answered ·

some AGM's do require a minimum charge rate of 10% - depending on the plate chemistry. However, for significantly large banks this becomes a major problem. Most AGM's will need to spend about 4 hours per week at recommended Absorption voltage, compensated for temperature. This is another good reason to move to lithium batteries - these requirements are no longer present. Batteries can be cycled from 20% to 80% or more without damage if you only get to 40 or 50%. Cycle efficiency is also a lot higher - about 96% c/f 40 - 60% for AGM.

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