Using oversized "dead" batteries

stephendv
stephendv Solar Expert Posts: 1,571 ✭✭
in Off Grid Solar & Battery Systems #1
I've noticed that some forklift companies will consider their batteries "dead" if they can't hold on to 80% of the rated capacity. So I was wondering whether you can still use such batteries if you oversized them? I.e. if I needed 500Ah in my RE system and I found a 900Ah forklift battery that was considered "dead" because it only held 700Ah of charge - would it still have a good useful life as a 500Ah battery?
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Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: Using oversized "dead" batteries

    i'm sure that they will continue on for a time being able to deliver that much capacity, but don't forget they are on their way out and that that time is short.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #3
    Re: Using oversized "dead" batteries

    I guess I'd like to know whether batteries degrade in a straight line, or is it a curve that will drop off suddenly?
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  • Dapdan
    Dapdan Solar Expert Posts: 330 ✭✭
    #4
    Re: Using oversized "dead" batteries

    I would say it is a straight line given the life of a battery is given in cycles and all the graph indicating this i have seen are straight lines.

    Using my limited experience with testing and recoverying batteries (only about 2 years) I can further testify that they don't drop off a cliff since I have been using used batteries for the past two years to run my entire home off grid and they have not failed me yet. Right now I have several used large AGM bank ranging in "capacity" of 900Ah to 1600Ah at 24V. So I would say go ahead and get that forklift bank, if you don't someone else will.

    Cheers...
    Damani
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: Using oversized "dead" batteries

    i know this isn't answering you, but do know that it won't take anywhere near as long to reach the next 20% reduction in capacity than it took for the first 20% reduction. it's hard to say specifically as even with identical batteries that time can vary greatly. most battery manufacturers consider that 80% mark as the end of life for the battery.
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