which bettery do you recommend?

VanDeusen
VanDeusen Solar Expert Posts: 129 ✭✭✭✭✭
in Solar Beginners Corner #1
I am going after batteries today for my solar system. I use apprx. 100kw per month. I was told to get a 6v 234amphr battery. What would you recommend for a battery?


and how many?


Thanx in advance!
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #2
    Re: which bettery do you recommend?

    If you use 100 kwh per month, that is around 3400 watt-hours per day. Batteries should be 3-5x that, so roughly 1000 to 1500 AH total for a 12 volt system.
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  • VanDeusen
    VanDeusen Solar Expert Posts: 129 ✭✭✭✭✭
    #3
    Re: which bettery do you recommend?
    Windsun wrote: »
    If you use 100 kwh per month, that is around 3400 watt-hours per day. Batteries should be 3-5x that, so roughly 1000 to 1500 AH total for a 12 volt system.

    so that means then get 4 of the 6v 234amp hr batteries? And why 6v instead of 12? I understand that when you take 2-6v you can series them and get 12v so does that also mean that 2 of them will give me a 12v at 468 amp hours? thanx
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #4
    Re: which bettery do you recommend?

    w
    hen you take 2-6v you can series them and get 12v so does that also mean that 2 of them will give me a 12v at 468 amp hours? thanx

    No you double the voltage and the current stays the same in a series connection so 12 volts at 234 amps. When paralleled you double the current and the voltage stays the same.
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  • VanDeusen
    VanDeusen Solar Expert Posts: 129 ✭✭✭✭✭
    #5
    Re: which bettery do you recommend?
    mikeo wrote: »
    w

    No you double the voltage and the current stays the same in a series connection so 12 volts at 234 amps. When paralleled you double the current and the voltage stays the same.



    so then why get the 6v? appose to the 12v battery? Thanx
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #6
    Re: which bettery do you recommend?
    so then why get the 6v? appose to the 12v battery? Thanx

    High current batteries are sold as 6 volt batteries or 2 volt cells because they are so heavy to handle. An L16 360 amp hour battery weighs in at 115 pounds, if it were sold as a 12 volt battery then the weight would be too much at 230 lbs for most of us to handle. IHTH
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  • VanDeusen
    VanDeusen Solar Expert Posts: 129 ✭✭✭✭✭
    #7
    Re: which bettery do you recommend?
    mikeo wrote: »
    High current batteries are sold as 6 volt batteries or 2 volt cells because they are so heavy to handle. An L16 360 amp hour battery weighs in at 115 pounds, if it were sold as a 12 volt battery then the weight would be too much at 230 lbs for most of us to handle. IHTH

    ok so YOU recommend 6v and what is the MIN. amp hr per battery I should be going after today? and I AM hooking the 6v in series right? pos to neg and neg to pos?
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #8
    Re: which bettery do you recommend?
    Ok so YOU recommend 6v and what is the MIN. amp hr per battery I should be going after today? and I AM hooking the 6v in series right? pos to neg and neg to pos?
    I would need more information to determine battery size based on more then just the 1000 kwh month you stated as expected usage. How large of an PV array are you installing? Is it properly sited? Are you tied to a particular battery voltage?
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  • VanDeusen
    VanDeusen Solar Expert Posts: 129 ✭✭✭✭✭
    #9
    Re: which bettery do you recommend?
    mikeo wrote: »
    I would need more information to determine battery size based on more then just the 1000 kwh month you stated as expected usage. How large of an PV array are you installing? Is it properly sited? Are you tied to a particular battery voltage?

    I am using 120w solar panels. (3 in total so far working my way up to 20) I am using a xantrex 40a multistage charger, I currently have 10 deep cycle batteries on the system. (drains fast) I am using a 30amp sunforce controller.
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #10
    Re: which bettery do you recommend?
    I am using a xantrex 40a multistage charger
    At what voltage does your charger work, 12 volt, 24 volt or 48 volts?

    Based on your expected 2400 watt array, 20 x 120 watt panels, you should consider either a 24 volt or 48 volt battery bank. If tied to a 12 volt system then you will be limited to around a 1kw array ( 8 120 watt panels) and need an 80 amp charge controllers to support the array power of 66 peak amps. Battery size to match this array would be around 660 amp hours at 12 volts and would fall far short of your anticipated 100 kw/hrs per month usage( 3.3 kwh/day).
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  • VanDeusen
    VanDeusen Solar Expert Posts: 129 ✭✭✭✭✭
    #11
    Re: which bettery do you recommend?
    mikeo wrote: »
    At what voltage does your charger work, 12 volt, 24 volt or 48 volts?

    Based on your expected 2400 watt array, 20 x 120 watt panels, you should consider either a 24 volt or 48 volt battery bank. If tied to a 12 volt system then you will be limited to around a 1kw array ( 8 120 watt panels) and need an 80 amp charge controllers to support the array power of 66 peak amps. Battery size to match this array would be around 660 amp hours at 12 volts and would fall far short of your anticipated 100 kw/hrs per month usage( 3.3 kwh/day).

    thats really on the high side because my kill a watt doesnt even show me using more then 1.5kw a day.
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