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  • 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

    Re: Charging a Sealed Lead Acid Battery

    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.
    Home system- 20 - 200W Evergreen blems, 2 Classic Lites, E-Panel, 2 Prosine 1800 watt inverters, 800AH 24V forklift Batt, up and running 1 Classic Lite and 14 Suntech 185W in spare room.
    Experience with Pulse/Trace PC250 Power Center, Original Rouge CC, 80-4/5watt 6v panels, Odds and extras,

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    • #3

      Re: Charging a Sealed Lead Acid Battery

      Re: Charging a Sealed Lead Acid Battery

      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.
      Off-grid: 6.12kW SolarWorld, 8 Trojan IND13-6V, XW6048, 2 XW MPPT60-150, 10kW Generac, 5kW Champion

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      • #4

        Re: Charging a Sealed Lead Acid Battery

        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.
        100% Off Grid @ 51* 46' N lat 124* 44' W long

        New House system: coming - 2 arrays @ 2240W
        CL150&Epanel 4 @140 W 12v PVs , 24V C&D AT-15P AGM @ 950Ah, Linksys wet54g - WiFi bridge, Cotek ST1500W inverter,
        TBS Omni-charger 30a-24v, ,
        + CL150 4 @140W 12 V panels, 24V C&D AT-15P AGM @ 950Ah
        Honda Eu3000is,Eu1000is

        Guest cabin system: 3 - 70W panels to BS 2000e CC, with 2 - 100 ah 12v SAFT wet NiCd's , 600W TSW Inverter

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        • #5

          Re: Charging a Sealed Lead Acid Battery

          Re: Charging a Sealed Lead Acid Battery

          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.

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          • #6

            Re: Charging a Sealed Lead Acid Battery

            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).
            6 - Trina 235 Watt panels, TriStar MPPT60 CC, 8-AGM 305AH 6V batts, Magnum MS4024PAE inverter, ME-BMK battery Monitor, ME-ARC Remote Control, MidNite Solar MNDC250, 10KW Generator

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            • #7

              Re: Charging a Sealed Lead Acid Battery

              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.

              -Bill
              20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

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              • #8

                Re: Charging a Sealed Lead Acid Battery

                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...

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                • #9

                  Re: Charging a Sealed Lead Acid Battery

                  Re: Charging a Sealed Lead Acid Battery

                  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.
                  http://tinyurl.com/LMR-Solar
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                  Grundfos 10 SO5-9 with 3 wire Franklin motor (1/2hp 240V 1ph # 214505 ) on a timer for 3 hr noontime run - Runs off PV
                  Powerfab poletop PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe battery | 15, Evergreen 205w "12V" PV | Midnight ePanel || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT

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                  • #10

                    Re: Charging a Sealed Lead Acid Battery

                    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...
                    100% Off Grid @ 51* 46' N lat 124* 44' W long

                    New House system: coming - 2 arrays @ 2240W
                    CL150&Epanel 4 @140 W 12v PVs , 24V C&D AT-15P AGM @ 950Ah, Linksys wet54g - WiFi bridge, Cotek ST1500W inverter,
                    TBS Omni-charger 30a-24v, ,
                    + CL150 4 @140W 12 V panels, 24V C&D AT-15P AGM @ 950Ah
                    Honda Eu3000is,Eu1000is

                    Guest cabin system: 3 - 70W panels to BS 2000e CC, with 2 - 100 ah 12v SAFT wet NiCd's , 600W TSW Inverter

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                    • #11

                      Re: Charging a Sealed Lead Acid Battery

                      Re: Charging a Sealed Lead Acid Battery

                      I am considering 13.5V to be 100% charged and 10.5V to be 0% charged. The battery will never be lower than 10.5V. (Actually it is a 24V system with two 12V batteries in series.) So given that the battery will be 10.5 minimum, I hope the "intelligent battery charger" will not over-current the battery.

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                      • #12

                        Re: Charging a Sealed Lead Acid Battery

                        Re: Charging a Sealed Lead Acid Battery

                        Repeated discharge to 10.5 Volts (21) will seriously shorten battery life. Charging to only 13.8 likewise. Please read the battery FAQ's: http://www.solar-electric.com/deep-c...ttery-faq.html
                        1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

                        Ohm's Law: Amps = Volts / Ohms
                        Power Formula: Watts = Volts * Amps

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                        • #13

                          Re: Charging a Sealed Lead Acid Battery

                          Re: Charging a Sealed Lead Acid Battery

                          coachdad nailed it with the formula, but bill is right that the absorb time can get extended with deeper cycling, especially with some other agm brands as their charge efficiency may not be as good as the sunxtender for lower efficiencies equal longer charge times for the same amps in.

                          as to the charger it may be necessary to be sure to place the additional load on it to keep the charger from pumping too many amps into the battery. this could result in overheating and warped plates to name a few so do not exceed the max charge rate to preserve your battery.
                          NIEL

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                          • #14

                            Re: Charging a Sealed Lead Acid Battery

                            Re: Charging a Sealed Lead Acid Battery

                            Originally posted by diego96 View Post
                            Powersonic sealed lead acid battery.
                            Check out their tech-manual which provides additional information (and a lot of it!) beyond the battery spec sheet. Even with that, it is easy to miss as it is the last paragraph of the document.

                            http://www.power-sonic.com/technical.php

                            Powersonic states that generally, you divide the rated battery capacity by the charge amperage and multiply by 1.75 to get hours. If you know the amount you have discharged, you can also base it on that instead of rated capacity.

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