Batteries

stooper2
stooper2 Solar Expert Posts: 41 ✭✭
in General Solar Power Topics #1
Hello All,

A quick question if I may regarding batteries.

Lets assume I need 740ah @ 24 volts for my solar system.
I can accomplish this 2 ways.

1. I can series 4 - 370ah batteries and parallel them with another bank of the same to give me 740ah.

2. I can series 2 - 370ah batteries and parallel these with another bank of the same to give me 740ah too.

What's the best way to determine if I should be using 4 or 8 to reach 740ah?

Thanks very much for the help.
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Comments

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    Re: Batteries

    series strings share current better than parallel strings.

    your config, if you use 6V batteries, will have more interconnects, and smaller batteries, than 12V batteries would present you.

    6V may be easier to trouble shoot a bad cell, 12V has less interconnects to troubleshoot.

    Do you prefer to lift 1 heavy 12V battery, or 2 lighter 6V ?

    (you didn't mention cell voltage, so I'm assuming 6V & 12V batteries)
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  • stooper2
    stooper2 Solar Expert Posts: 41 ✭✭
    #3
    Re: Batteries

    Thanks for the reply, the batteries would all be 6 volts
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
    Re: Batteries

    stooper2,
    if all of the batteries are 6v then #2 would windup at 12v because you specified 2 in series. #2 would have to be 2-12v batteries in series and paralleled with identical strings to come up with the required current. you can do it either way and there are advantages and disadvantages to both, but the bottom line is it needs to be 24v with at least 740ah.
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  • stooper2
    stooper2 Solar Expert Posts: 41 ✭✭
    #5
    Re: Batteries

    Thanks for the replies.

    K - Maybe I'm off on this one so I'll try and explain it again.

    I will be using 6 volt 370ah batteries for this and puting them in a configuration to get 24 volts @ 740ah.

    For the first set, it will be as follows-

    (Figure 1) 2 - 6 volt batteries in series to give me 12 volts @ 370ah, then another 2 - 6 volt batteries in series to give me 12 volts @ 370ah- parallel these 2 strings to give me 24 volts @ 740ah.

    (Figure 2) 4 - 6 volt batteries in series to give me 24 volts @ 370ah, then another 4 - 6 volt batteries in series to give me 24 volts @ 370ah and then parallel these 2 strings to give me 24 volts @ 740ah.

    The question I have is, how do I determine how many batteries to use to get 740ah because I can get the same amp hour reading with either 4 batteries (Figure 1) or 8 batteries (figure 2)?

    Thanks in advance,

    Rick
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #6
    Re: Batteries

    "Figure 1" is wrong because you are paralleling 2 12 volt sets, which gives you 12 volts.

    You need 8 batteries.
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  • stooper2
    stooper2 Solar Expert Posts: 41 ✭✭
    #7
    Re: Batteries

    Hey - I see the problem here.

    You're right, the first will be 12 volts - my bad.

    Thanks for your help with this one.

    I'll go hide in the corner now for a bit.
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  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    #8
    Re: Batteries

    your first scenario of 2 srings of 2 batteries (6V, 370ah) would equate to 740ah at 12V NOT 24V. Remember paralleling adds the amp hour capacity, serries strings add the voltage; so two strings of 12V batts at 370ah could be serries connected to make 24V 370ah, OR parallel connected to make 12V 740ah...
    if the batteries are the same size you can't make the same amount of power from half the number of batteries....
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
    Re: Batteries

    gee, i thought i said it came out to be 12v. i guess i confused him?:confused:
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  • stooper2
    stooper2 Solar Expert Posts: 41 ✭✭
    #10
    Re: Batteries

    Hello all - You didn't confuse me. let's just say I was trying to get more for less.

    I understand PERFECTLY now.

    Again, thanks for all of your help - greatly appreciated,

    Rick
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