Do I have a battery problem?

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  • BB.BB. Super Moderators, Administrators Posts: 29,235 admin
    Re: Do I have a battery problem?

    What was the SG levels before "equalization" and what was your measured/estimated state of charge?

    Equalization is typically once a month, and only for a few hours at a time.

    Specific Gravity should be measured (or temperature corrected) to ~77F. The range between 100% charged and 100% discharge is, roughly; 1.265 for a fully charged cell, and 1.13 for dead.

    1.265-1.130=0.135 spread.

    0.135 / 10 (10% steps) = ~0.0135 sg change per 10% change in charge level...

    The cell at 1.215 sg vs 1.270 charged--that is roughly a 0.06 point drop, or 0.06/0.0135=44% discharged (56% state of charge) after your extreme equalization...

    That one cell does not look good--and could affect the entire string's capacity. Replacing the one battery may be a requirement to get the rest of the string operating well again.

    I forget what the Battery Mfg's recommend-but if you have cells at 0.030 or greater spread in Specific Gravity--those cells are having problems (battery itself, equalization needed, age, cabling/connections, deficit charging, etc.)...

    Your equalization charge was probably too much... Keep the acid at 115F or less. And, you should have been "over-charghing" the battery capacity by 10% or so.

    If all of the batteries were bubbling--then the acid was probably well mixed. If some batteries did not bubble--it is possible that the acid is still stratified (not mixed)... The "heavy" acid at the bottom of the battery and the "light" weak acid at the top (don't think this is an issue here).

    Measure the Specific Gravity in the morning after a normal load and see what the readings are... Otherwise, see if you can borrow or justify a load tester and check each battery--but it will probably just tell you what you already know (one or more batteries are starting to go south).

    Trojan has this recommendation:
    Equalizing (fooded/wet batteries ONLY) 3.4.2.
    Equalizing is an overcharge performed on fooded/wet batteries after they have been fully charged. Trojan recommends equalizing only when batteries have low specifc gravity, below 1.250 or wide ranging specifc gravity, 0.030, after fully charging a battery. Gel or AGM batteries should never be equalized.
    • Confrm that the batteries are fooded/wet
    • Check electrolyte level to make sure plates are covered with water before charging
    • Check that all vent caps are secured properly on the battery before charging
    • Set charger to equalizing mode
    • The batteries will gas (bubble) during the equalization process
    • Measure the specifc gravity every hour. Discontinue the equalization charge when the gravity no longer rises

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Do I have a battery problem?

    good to hear the sg readings came up some. the weaker cell will be a problem some time down the line i suppose. any way you could kick just only that battery in the pants with an eq charge (an hour should suffice)? if not, take another you deem next in line and run an eq on just those 2 batteries in a 12v configuration and see if it does any good. if you decide to do nothing i wouldn't blame you or be surprised, but you need to investigate further why the sg readings were falling in the first place as it may have been something being overlooked.
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