charge rates for agm batteries

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mahendra
mahendra Solar Expert Posts: 180 ✭✭✭
in Off Grid Solar & Battery Systems #1
hi there i am planning to add a few extra panels on my off grid system and want to know if the charge rate would exceed the recommended charge a agm battery can accept without damage.To be specific it deka agm batteries.So whats the maximum charge rate these can accept.thanks in advance.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: charge rates for agm batteries

    This will sound like a non-answer: ask Deka.

    Some AGM makers like Concorde claim some extremely high current tolerances for certain of their batteries. In general AGM's will take more than FLA's, but to know the actual upper limit you have to ask the maker about the particular model you're using.

    As a rule, an occasional 20% current rate won't harm even an FLA.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
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    Re: charge rates for agm batteries

    their max is 30% of the 20hr ah rating. the 2v cells are 15%. not sure why that is.
    http://www.dekabatteries.com/assets/base/1913.pdf
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  • mahendra
    mahendra Solar Expert Posts: 180 ✭✭✭
    #4
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    Re: charge rates for agm batteries

    i am using the 8d 12v deka intimidator.tried to get some info from deka but was unsuccessful,thats why am here .Thanks
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  • mahendra
    mahendra Solar Expert Posts: 180 ✭✭✭
    #5
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    Re: charge rates for agm batteries

    thanks that link did helped just wanted to know if i am within the ball park there because i would be around 24% wanted to know if i am exceeding the limits charge rate
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
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    Re: charge rates for agm batteries

    only way to be 100% sure is to contact them. that particular battery can be subjected to alternator charging so it may have a higher rating, but don't count on it unless you hear it from them. odds are the alternator would not sustain higher than 30% for very long before the charge rate would cut back so i'm not sure if they allow for higher bursts of charge power. the pdf chart i linked to is basically for a sustained rate of charge.

    if you contact them please inform us of what is said, but at 24% i'd say you are ok.
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    #7
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    Re: charge rates for agm batteries

    In sealed lead acid batteries there is gas recombination but there is a limit to rate of recombination. (gas being hydrogen off negative plates and oxygen off positive plates from fracking water to dissipate overcharge)

    Recharging is a progressive process. Surface sulfide get easily recharged. Deeper penetration requires longer time. Raising the voltage helps get the recharge penetration at the detriment of fracking water on areas already charged.

    30% C recharge current up to about 2.2 volts per cell (13.2 volts for six cell battery) is pretty safe. Up to that voltage little gasing is created because most of the energy is going into desulfating recharge. Beyond that voltage it depends on battery type and construction ability to dissipate gases.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #8
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    Re: charge rates for agm batteries

    Your charging voltage is probably more critical than charging current limiting.

    I.e., any lead acid that is well discharged (less than 80% State of Charge) can take in excess of 20% charging current and do well (most energy goes into chemical recharging, little into heat or hydrogen/oxygen generation).

    As the batteries become "full" and the battery charging voltage rises, then more of the non-optimal effects occur (heating/gassing). If you limit the charging voltage (AGM/GEL require lower absorb voltage, and no elevated equalization voltages), then your batteries should naturally limit their input current (I believe Concorde has no current limits if you respect their charging voltage set points).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mahendra
    mahendra Solar Expert Posts: 180 ✭✭✭
    #9
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    Re: charge rates for agm batteries

    i dont think i have problem with the voltages as those are printed on the battery label and of course my batteries are charged by solar panels hooked up to a midnite classic
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