Used battery AH question

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raydias
raydias Solar Expert Posts: 68 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
i just bout 2 of the following batteries and wanted to test my math out.

http://www.mkbattery.com/images/8G22NF.pdf

I put them on a charger and the readings are stable at 13.2 volts and 3.2 amps.
so that means they have 42.24AH capacity

is that correct?

is there a way to recondition them closer to the original AH rating?

thanks
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #2
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    Re: Used battery AH question

    Ray,

    I am a little confused... You really cannot judge the AH capacity by an arbitrary charging current/voltage (I guess you could make a chart from a particular battery model and use it to estimate capacity).

    Your charging voltage of 13.2 volts is quite low for either charging or floating a battery. And 3.2 amps at 13.2 volts is actually quite a high charging current--indicating that the battery may be fairly discharged at this point.

    Also, be careful with Gel batteries--They tend to take high charging voltages and currents very badly. Bubbles can form at the plate/electrolyte interface and loose battery capacity.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
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    Re: Used battery AH question

    ray,
    did you measure the voltage of the batteries before you put any charge to them? that could give a possible glimpse into their condition. gels are picky on their charge too just like agms. it looks like the 14.4v absorb setpoint and maybe 13.5v for float are good compromises. try not to overfeed or underfeed the batteries and they are more sensitive to too much charge current than other types so figure no more than about 10% charge rate to be on the safe side unless you see otherwise from the manufacturer. as to their current condition all i can say is use them and see if the load over time correlates with the ah rating. (load test)
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