Good Use of batteries.

jacknifejacknife Registered Users Posts: 6
I have been fooling around with solar for about 6 months. I started out with 4 - 12 volt golf cart batteries and purchased a couple of 24 volt 225 watt solar panels. In the meantime I found an excellent buy on 12 volt Lifeline AGM 255 Ah batteries. and got 6 of them. Wow what a find.......... Well now the problem starts. What do I do now. I would like to build an off grid 24 volt DC system that produces 220 volts ac at about 4000 watts. The more I research the more stumped I become, Maybe I am looking too hard........... Any thoughts about this ? I also have a 440 amp Coleman air charge controller.My batteries are wired in a 24 volt configuration just like the one suggested on this site, and they are charged to 25.6 x3 trying to build a 1500ah battery bank. I may have the cart before the Horse but I got the batteries for $100 each (government surplus) never used 2 years old and had 12.5 volts when I got them and now they are holding a 12.8 charge. I believe they will be a good basis for a strong system, But an my grandson says " What do I do Now". Right now I am just keeping them charged up. But I really want to run with this thing.


  • SevenSeven Solar Expert Posts: 292 ✭✭
    Re: Good Use of batteries.

    I will be the first one to ask what your loads are. The basis of any system depends on that answer. You talk about a 24v system, but you mention 6, 12v batteries. That puts you having three parallel strings of 24v at a total of 765ah. That will require an 80a charger and a good number of panels to feed it.
  • BB.BB. Super Moderators, Administrators Posts: 33,327 admin
    Re: Good Use of batteries.

    4kW is a good sized system... Do you need 240 VAC or 120/240 VAC split phase (typical North American Home)?

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Good Use of batteries.

    Definitely cart-before-the-horse. :roll:

    If you'd bought eight 12 Volt 225 Amp hour batteries you could have a 48 Volt 450 Amp hour battery bank.

    But to expand on what Bill said; what are you looking for in power output? Not just Voltage, but also maximum Watts at any given time and, most importantly, total Watt hours?

    "Building" a 1500 Amp hour battery bank is not a sensible undertaking. For one thing, you can only "build" a battery bank by buying all you need at one time. Buying some now and more later and putting them together is bad practice; they inevitably will be at different capacity from age alone and the 'lesser' batteries will draw the 'greater' ones down. For another, 1500 Amp hours requires 150 Amps f potential peak charge current and that is a lot. It means two charge controllers, for one thing. Two big ones like FM80's.

    Putting your six batteries into a 24 Volt configuration gives you 675 Amp hours, which is quite a lot. Potentially 8kW hours of power. There is no configuration of 225 Amp hour batteries that works out to 1500, btw.

    Stop spending money and start figuring out where you want to go with this. Buying stuff on the basis of "it's a good deal" can end up being a lot of money spent on a whole lot of equipment that won't do the job. That's no bargain at all.
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