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Small Cabin Forum / Off-Grid Living / charging batteries with solar panels
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sparky30_06
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# Posted: 16 Aug 2017 08:40 - Edited by: sparky30_06
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so I have 2 12 volt batteries in series to give me 24vdc. can I use 2 12volt solar panels to charge the batteries. one to each battery?

These are small lead acid gel batteries that you would find in emergency lights. These system is nothing high draw. I have a 12 volt timer pulling off one battery, a small 24 volt air compressor pulling of the second battery and a 24VDC solenoid pulling off both. The compressor run for about 30 seconds twice a day and the solenoid is energized for the same amount of time.

ICC
Member
# Posted: 16 Aug 2017 19:47
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Quoting: sparky30_06
so I have 2 12 volt batteries in series to give me 24vdc. can I use 2 12volt solar panels to charge the batteries. one to each battery?


Each with its own charge controller? It would work but would be not normal

sparky30_06
Member
# Posted: 17 Aug 2017 06:42
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Thank ICC but this build will need to be small and cheap. No charge controller. Right now I have 12 volt system that just runs a timer and motor, and it just has a small solar panel that trickle charges the battery. keep in mind that the load is minimal and only runs 30 seconds a day, twice a day so I'm not trying to power a house.

ICC
Member
# Posted: 17 Aug 2017 10:28
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Well then there are a couple of questions. You have gel cell batteries. They are the least tolerant of lead acid with regards to overcharging. Will there be danger of overcharge on a good sunny day? Are the panels small enough that the trickle won't cook the batteries?

At the same time are the panels big enough to actually recharge the use at least almost every day? If the batteries don't get to a real 100% charge state at least a few times a week that is harmful as well.

Even those small, cheapest harbor freight CC units might be better than nothing.

sparky30_06
Member
# Posted: 17 Aug 2017 12:30
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My mistake they are SLA not gel. The current panels I have on the 12v units are tiny guys, like 6" x 8" and just have them plugged directly into the battery and have had no issues. I'll have to find out how many watts they are.

Thanks for helping, I'm a pro at high voltage, electrician for 20+ years but figuring this solar stuff for some reason is tripping me up. I can wire up motor starts, switch gear, plcs, houses, factories and industrial buildings but this DC stuff creates magic smoke LOL!!

old243
Member
# Posted: 17 Aug 2017 21:20
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Sparky, That is a like myself. Worked with AC all my life. Dc baffels me. Have to think it all through , even then it doesn't always make sense. old243

sparky30_06
Member
# Posted: 22 Aug 2017 10:58
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old243
I'm glad I'm not the only one!!!!

I'll figure this out sooner or later, or smoke it!

pizzadude
Member
# Posted: 22 Aug 2017 17:40
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I believe you can wire the panels in series to give you 24vdc. Save yourself some trouble and pick up a cheap controller to charge the batteries too👍

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