question

greekgeek avatar image

a big thank you and a battery question

i would like to thank everyone who spent time answering my stupid questions and helping me out to fix my solar problems. i changed my solar panel setup from 12v to 24v, got a new battery and now i harvest about 850 wh per day.that's a huge improvement that allowed me to power a fridge among other things (a word of advice for off-gridders, buy a dual function chest fridge, huuge difference form ordinary ones) .

a question about batteries: since a battery is considered to be charged when >12.8 or so, what if the battery is charged at 13v or more? how charged is considered? my battery is at 12,64v every morning, what state of charge is that considered to be? (gel vrla battery)

cheers

battery capacity
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3 Answers
rickp avatar image
rickp answered ·

I believe a 12V gel battery is charged at over 13 volts as a normal practice, 13.5 to 13.8. Check your manufacturer’s site for guidance, but all battery types require voltage in excess of their 100% reading in order to attain that state.

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russ-tanner avatar image
russ-tanner answered ·

Finding battery specs can be daunting.

I have two Duracell Ultra AGM 70 ah for our RV. By taking the long road, I found these are made by EastPenn.

They have a pretty nice read on AGM and gel batteries and charging volts if it can help. I had to really dig for this. I tried calling Duracell with no luck.

Batteries plus (who sells the Duracell brand) had nothing but to tell me but who makes Duracell batteries, EastPenn or aka, Deka.

There is great guidance for charging voltages here. For Gel batteries, a max charging of 14.1 volts is indicated.

http://www.eastpenn-deka.com/assets/base/0139.pdf

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wild-thing avatar image
wild-thing answered ·

For AGM batteries, charge with 14.1 - 14.4 V, depending on the batteries data sheet. After the current goes down to a lower current (e.g. 1-2A for an 100Ah battery), load with float voltage, typically Ufloat = 13.6V. If you charge for a long time with a voltage higher than Ufloat, you will kill the battery. That was a very short version - google for details

By the way, Victron chargers will handle all this pretty smooth.

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