Understanding battery terminology

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Arkansasoffgrid
Arkansasoffgrid Solar Expert Posts: 117 ✭✭
in Solar Beginners Corner #1
A 6v battery labeled 215 20 hour / 105min@ 75A, is this referring to a 215 AH battery? It's a golf cart battery at Sam's.
8-420AH US Battery L-16s, Midnite Classic 150cc, Whiz Bang Jr, Magnum MS4448PAE inverter/charger,  4590w Canadian Solar panels. Honda EU2000i generator.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #2
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    Re: Understanding battery terminology
    Arkansasoffgrid wrote: »
    A 6v battery labeled 215 20 hour / 105min@ 75A, is this referring to a 215 AH battery? It's a golf cart battery at Sam's.

    A battery's capacity is a function of how fast you draw it down. If you drew 10.75 amps for 20 hours you would get the full 215 ah. If you draw 75 amps for 1.25 hours, it is a 93.75 ah battery.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
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    Re: Understanding battery terminology
    Arkansasoffgrid wrote: »
    A 6v battery labeled 215 20 hour / 105min@ 75A, is this referring to a 215 AH battery? It's a golf cart battery at Sam's.

    Yes. The 20 hour rate is what we use a standard capacity measure for RE applications.
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  • Arkansasoffgrid
    Arkansasoffgrid Solar Expert Posts: 117 ✭✭
    #4
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    Re: Understanding battery terminology

    So two strings of eight in parallel would equal 430 amp hours. Or 107.5 amp hours at 25% DOD. And would also be in the 10% charge rate with 4000 W solar panels.
    8-420AH US Battery L-16s, Midnite Classic 150cc, Whiz Bang Jr, Magnum MS4448PAE inverter/charger,  4590w Canadian Solar panels. Honda EU2000i generator.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: Understanding battery terminology
    Arkansasoffgrid wrote: »
    So two strings of eight in parallel would equal 430 amp hours. Or 107.5 amp hours at 25% DOD. And would also be in the 10% charge rate with 4000 W solar panels.

    Yes: two parallel strings of eight in series = 430 Amp hours @ 48 Volts. 107.5 Amp hours @ 25 % DOD, approximately 5 kW hours.

    10% charge rate would be 43 Amps which works out to 2680 Watt array:
    43 Amps * 48 Volts / 0.77 derating = 2680 Watts.

    A 4kW array would provide 64 Amps @ 48 Volts. Rather more than is needed.
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  • Arkansasoffgrid
    Arkansasoffgrid Solar Expert Posts: 117 ✭✭
    #6
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    Re: Understanding battery terminology

    These batteries are available for around $100 each including core charge, this will be my learning/starter set. Does it make more sense to buy a 4K solar array now, or add panels when I get the next set of batteries which I plan to be 6-700 ah. Planning on magna sine 4448 PAE inverter, and outback classic 150 charge controller.
    8-420AH US Battery L-16s, Midnite Classic 150cc, Whiz Bang Jr, Magnum MS4448PAE inverter/charger,  4590w Canadian Solar panels. Honda EU2000i generator.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: Understanding battery terminology
    Arkansasoffgrid wrote: »
    These batteries are available for around $100 each including core charge, this will be my learning/starter set. Does it make more sense to buy a 4K solar array now, or add panels when I get the next set of batteries which I plan to be 6-700 ah. Planning on magna sine 4448 PAE inverter, and outback classic 150 charge controller.

    If you can afford the panels now, buy them now. You can't be certain the same ones will be available later. In the meantime you may want to program a current limit on the Classic so the batteries aren't subjected to 64 Amps (although that's about 15% peak rate, about the upper limit).
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  • BEFUDDLED
    BEFUDDLED Registered Users Posts: 8 ✭
    #8
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    Re: Understanding battery terminology

    You just mentioned a starter/learning set. My hat is off to you for recognizing what I always read, that is, to go cheap, just a panel or two and a battery or two, cheap charge controller and cheap inverter to LEARN. I spent nearly $20K for a system including 16 6V 420am/hr batteries. I was not able to get the installation complete due to weather, illness and other issues, so the batteries just sat (I was told 90 days would be okay). After about 90 days, we started throwing a charge on them, two strings of 8 for 48, but ultimately, I have lost 6 of those batteries. The batteries I bought cost about $300 each. Now, I am struggling to find a battery charger that can do justice to 420 or 840 amp batteries at 48V. Wish I had spent about 2 grand or even less and LEARNED more about all of this. I still have everything in safekeeping, but I fear, no matter what, I will lose more batteries if I can not find the charging and maintaining solution until the installation can take place. I also have the Magna Sine 4448 PAE inverter, but I believe I have the Midnite Classic 160 charge controller, neither of which have even been uncrated, and 15 250 watt Canadian Solar panels. Punchline, my LEARNING has been and is very expensive.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #9
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    Re: Understanding battery terminology

    There are may good Inverter-Charger units out there--And the 48 volt ones have some pretty good charging capabilities (60+ amps for a 48 volt charger).

    If nothing else, if you can get the battery bank wired up and the inverter charger connected (to utility/backup genset--whatever you need)--And get that going, it may be worth the price to pay somebody to do that part of the install now and have the battery bank getting the charging it needs.

    Life is what happens when we are making plans. :cry:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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