Couple questions

Hi, New to the site and solar in general... I am wondering how many panels i should have at my off grid cabin. I have a 24v 3000w Growatt inverter with 3 panels (270w each) wired in series.. i think max input is 2000w of panels and 145v max...I have 8 lead acid 6v batteries - 4 wired in series and 4 more wired in series and then the 2 strings wired in parallel....Does this sound right and if one 6v battery has 215 AH what would my total AH be?

Thanks

If the panels are 60 cell then voltage will be ok with 3 in series. If the panels are 72 cell panels then you can only run 2 in series as 3 would be at
140 open circuit and real cold days even higher and above the 145 open circuit limit.

If the 6 volt batteries are 215 each then at 24 volts (4 series) then it would be 215 ah but at 24 volts
The watt hours will increase. (215 x 6 vs 215 x 24)

jpimlott said:

If the panels are 60 cell then voltage will be ok with 3 in series. If the panels are 72 cell panels then you can only run 2 in series as 3 would be at
140 open circuit and real cold days even higher and above the 145 open circuit limit.

If the 6 volt batteries are 215 each then at 24 volts (4 series) then it would be 215 ah but at 24 volts
The watt hours will increase. (215 x 6 vs 215 x 24)

Click to expand...

Panels are 60 cell - just wondering how many more i can run and in what configuration.

i have 4 batteries tied together in series and another 4 batteries in series and then have the 2 strings of batteries parallel....would that be 430AH?

yes that would be 430 AH as parallel adds amps and watt hours

I think four is the max in series. eight total all facing south for 12 with some South East and some South West (nothern Hem)
You would need to measure your open circuit voltage with four in series.
I am running 3 24 volts panels and seeing about 100 volts open circuit.
Needs to be check at noon with cold weather for highest voltage,
You still want 10 volts or more head room ( 135 volts max) for saftey,
dont want to let the magic smoke out.

You can go over the 2000 watts some but better to spread it out during the day.

About double what you now have.

Lead-acid likes charging at ~ 1/8C. Assuming bulk charging is going to start at ~26V, and you include a 85% fudgefactor for real-world panel output, the math looks like this....

{[(215Ah X 2 strings)/8] X 26V}/85% = 1644W

So, I would get three more of those 270W panels, and wire a second parallel string of three, like the first one. That would be expressed as 3S2P.

That will keep those batteries happy. Right now, just those three panels will place charging somewhere halfway between bare minimum, and good.

While technically your batteries total 430 Ah, you should only discharge lead acid no more than 50%. So you want to charge at up to 430/8=54A, but only consider using 215 Ah at the most when discharging.