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Thread: Charging a Sealed Lead Acid Battery

  1. #1

    Default Charging a Sealed Lead Acid Battery

    Hi all,
    I'm trying to calculate the time to recharge a sealed lead acid battery to 100%. For example if I have a battery at 100%, and I discharge 10A for 1 hour, will it take exactly 1 hour to recharge the battery if my charger supplies 10A of charging current? Or will it take 1.1 hours, 1.2 hours, etc. Is there a term for that? ("charging efficiency?") I've looked on battery datasheets and I can't seem to find anything to answer my question.
    Thanks for any help.

  2. #2

    Default Re: Charging a Sealed Lead Acid Battery

    Pretty much, and my experience is from Flooded batteries, there is no correct answer. As batteries approach full capacity they can accept less current. You do get close to 1:1 - 1:1.1 correspondence in the 50%-85% with the charging voltage appropriate.
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  3. #3

    Default Re: Charging a Sealed Lead Acid Battery

    Quote Originally Posted by diego96 View Post
    I'm trying to calculate the time to recharge a sealed lead acid battery to 100%. For example if I have a battery at 100%, and I discharge 10A for 1 hour, will it take exactly 1 hour to recharge the battery if my charger supplies 10A of charging current? Or will it take 1.1 hours, 1.2 hours, etc. Is there a term for that? ("charging efficiency?") I've looked on battery datasheets and I can't seem to find anything to answer my question.
    It is up to you how much you put back. With flooded batteries, the more you put back, the more bubbling you get. So, by varying the amps you can vary the amound of energy that goes to bubbling and efficiency changes accordingly. The correct amount of bubbling is important to flooded batteries. Sealed batteries do not need bubbling, so you should get something close to 1 or slightly higher.

    The energy efficiency is worse than amp-hour efficiency because you charge at higher voltages and discharge at lower voltages.
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  4. #4
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    Default Re: Charging a Sealed Lead Acid Battery

    What does the maker recommend for charge parameters? Since they are sealed you should not EQ for one thing and, secondly the charge rate should be lower than FLA to avoid too much gassing... the H and O2 have to recombine into H2O.
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  5. #5

    Default Re: Charging a Sealed Lead Acid Battery

    Quote Originally Posted by westbranch View Post
    What does the maker recommend for charge parameters?
    Powersonic sealed lead acid battery. Constant current (max 22A) up to 14.4V, hold at constant voltage 14.4V until current drops below 750mA. Battery is 100% at this point.

  6. #6

    Default Re: Charging a Sealed Lead Acid Battery

    I don’t know if this is a universal formula but this is what the manual for Sun Xtender batteries says. The Sun Xtenders are AGM batteries. I believe that AGM batteries are considered to be “sealed lead acid”.

    Time to Reach Full Charge = [(DOD/100) X Rated Capacity (Ah) / Rated Output of Charger (Amp)] + 2 hours
    For example, charging a 100ah battery at 50% DOD using a 25A charger would take:
    Time to Reach Full Charge = [(50/100) X 100Ah/25A] +2 hours = 4 hours
    Note that this formula is approximate and the full charge state should be verified using the criteria: current drops below 0.5% of the rated capacity (0.5A for a 100Ah battery).
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  7. #7
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    Default Re: Charging a Sealed Lead Acid Battery

    That is what I use... But I would suggest that the time would be 2-4 hour range... The deep cycled the battery, the longer the "tail" of the charging cycle.

    Also, Concorde batteries are AGM sealed lead acid--But they claim to be "different" from other AGM batteries and are able to accept higher charging voltages (and currents) that other brands may not.

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  8. #8

    Default Re: Charging a Sealed Lead Acid Battery

    Another charger question.
    This is what my battery datasheet says: "Limit initial charging current to 22A."
    I'm looking at using a Xantrex TRUECharge2 40A charger. The reason for getting a 40A charger is because I want to sometimes power a load in addition to charging batteries.
    However if there is no load, will the charger try to force 40A into the battery? I assume that would damage the battery since the datasheet says limit to 22A...

  9. #9
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    Default Re: Charging a Sealed Lead Acid Battery

    Quote Originally Posted by diego96 View Post
    Another charger question.
    This is what my battery datasheet says: "Limit initial charging current to 22A."
    I'm looking at using a Xantrex TRUECharge2 40A charger. The reason for getting a 40A charger is because I want to sometimes power a load in addition to charging batteries.
    However if there is no load, will the charger try to force 40A into the battery? I assume that would damage the battery since the datasheet says limit to 22A...
    Yep. Maybe. If the battery was totally dead, it could pull the full 40A. But since you will have some charge in it, it will draw less, and as it approaches full, even less. That's why it takes such a long time to complete the last 20% of charge.
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  10. #10
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    Default Re: Charging a Sealed Lead Acid Battery

    As mike said, if the battery is deeply discharged the TC40 will attempt to put 40 amps into the battery. The acceptance rate is dependent on the battery SoC... If yours (TC40) is the same as mine, the display will show the Amps being delivered...
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    New House system: coming - 2 arrays @ 2240W
    CL150&Epanel 2 @140 W 12v PVs , 24V C&D AT-15P AGM @ 950Ah
    + CL150 2@120W 12 V panels, 24V C&D AT-15P AGM @ 950Ah
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    Guest cabin system: 3 - 70W panels to SB 2000e CC, with 2 - 100 ah 12v SAFT wet NiCd's , 600W TSW Inverter

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