Leisure Battery Performance Question

robvizi
robvizi Registered Users Posts: 3
in Off Grid Solar & Battery Systems #1
Hi, I bought a brand new sealed leisure battery Lucas 12v 75AH and after using it a few days and charging I fully charged it and was very keen to test, it its my habit;)
this is my load record:

start 13.10V
Used 2.2Amp for 10h withing 3 days and voltage dropped at 12.24V
Then used it 5h(with breaks) in one day at 2Amp load, voltage 12.19V
Next day 2h 2 amp load, voltage 12.05
And then 10h at 2Amp within next 2 days voltage now is 11.74V

That gives total 27h which I think is a bit weak.

Should I get this battery replaced?

Thanks
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Leisure Battery Performance Question

    Should you get the battery replaced? Does it do what you want it to? Yes = don't replace. No = different battery.

    Your testing is more or less meaningless. Voltage is not a reliable method of determining SOC.
    A 75 Amp hour (at the 20 hour rate) battery would in theory supply 3.75 Amps for 20 hours after which it would be totally dead. Usable capacity is unlikely to be more than half that, or 37.5 Amp hours. In basic math this would supply the 2 Amp load for 18.75 hours, at which point resting Voltage would be 12 Volts. Resting Voltage, btw, is taken after the battery has sat for several hours (preferably overnight) without current going in or out. You will always see some "rebound" in the process (immediate Voltage compared to resting Voltage).
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: Leisure Battery Performance Question
    robvizi wrote: »
    start 13.10V
    Used 2.2Amp for 10h withing 3 days and voltage dropped at 12.24V
    Then used it 5h(with breaks) in one day at 2Amp load, voltage 12.19V
    Next day 2h 2 amp load, voltage 12.05
    And then 10h at 2Amp within next 2 days voltage now is 11.74V

    That gives total 27h which I think is a bit weak.

    22ah+10ah+4ah+20ah=54ah total (27ah does not appear to be correct).

    Seems reasonable... By the way, don't let the battery set for days/weeks without recharging back >90% state of charge... You will sulfate the battery and drive it to an early grave.

    -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 ✭✭✭✭
    #4
    Re: Leisure Battery Performance Question

    in addition to not leaving the battery in a lower soc for long you should not be going below that 50% soc point that coot mentioned as it will rob you of some battery life and if you go low enough you could damage the battery by reverse polarity in a cell.

    also, do not let your battery only be charged up to 90% as you need to bring it up to 100% soc as not doing so creates a deficit charge and it will still sulfate.
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