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  • Battery question?

    Buying a very large 48 volt forklift battery & charger for a solar system. Just found out the charger is 36 volt so for a couple years it's been kept charged to 36 volts only. My question is do you think it's sulfated the battery of if I charge to 48 volt it will be OK? It'sin a forklift which seems to operate fine so I was gping to use the forklift until the panels are up. The battery weighs almost 4000# Thanks for the help!

  • #2
    Originally posted by flylo View Post
    Buying a very large 48 volt forklift battery & charger for a solar system. Just found out the charger is 36 volt so for a couple years it's been kept charged to 36 volts only. My question is do you think it's sulfated the battery of if I charge to 48 volt it will be OK? It'sin a forklift which seems to operate fine so I was gping to use the forklift until the panels are up. The battery weighs almost 4000# Thanks for the help!
    It's perfectly possible, maybe even probable. What KIND of charger?

    The question is really, is this a "charger for 36V batteries"?

    Or does the charger use 36VAC rectified?

    If the former, then, there is a good chance that there is "degradation" in the battery, since it will not have been fully charged, and there may be "sulfation". At least it has been charged, so it's possible that there is less damage than might be.

    If it is a rectified 36VAC, that's different. The peak voltage would have been about 50V, and that could at least maintain a 48V battery at a reasonable state of charge. It would not recharge one well, but given time it would probably happen.

    Get a good temperature compensated specific gravity tester, and check all the cells. Bad ones will never come up to a good gravity no matter how much voltage you apply, and they will gas off more water than any others.

    And, on discharge, they have low capacity, so they will discharge and then will likely reverse charge, doubling the net loss of voltage. You will probably end up bypassing any of those if you can do that and still use the battery.
    1601

    Keep eye on ball.
    Hashim Khan

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    • #3
      I think it's a recified 36v 3 phase charger & the owner did keep it charged to 36v. I've had good luck with deep cycle batteries but wasn't sure where sulfation would start as it's been 25% low on charge for a long time. The forklift runs & operates fine but I'm sure would not run as long as 48v would.
      Here's another question thus model lift truck was offered in 36 or 48v in the same model. What would they have changed between the 2?

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      • #4
        They would have to change number of battery cells and probably cell size, also most likely motor ratings for drive and pump motors.

        Maybe something about the way the lights and other "housekeeping" stuff is powered.
        1601

        Keep eye on ball.
        Hashim Khan

        Comment


        • #5
          Another question, if it's a rectified charger starting at 50v shutting off at 36v can I change something to make it shut off at 48v?

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          • #6
            I should have considered the 3 phase... ours were single phase.

            With 3 phase, the 36V may BE just a bit higher, maybe 42 to 45V. That's about the bulk absorption voltage for a 36V battery. The average voltage for 3 phase rectification is different from single phase, given same input.

            if it is an electronic type, there may be a way to make it the other voltage, because it probably starts a bit higher than needed and electronically adjusts the voltage output. That much higher may be too much difference though.

            If it is an old style timer type, the voltage will be what it is, set by the transformer tap, but you may get a higher voltage by selecting a higher current tap, if the thing has a choice..

            if any damage could have been done, it already was done, so it may just be what it is.... have you measured the battery output voltage to see?
            1601

            Keep eye on ball.
            Hashim Khan

            Comment


            • #7
              Only with a voltmeter, I'm checking it with a hydrometer in the morning. I know the cells come apart, the plates are thick & they rebuid them so I wonder how hard it would be to rebuild any bad cells? I'm sure I can sell the charger for enough to get a 48v golf cart charger.
              Last edited by flylo; 01-24-2016, 06:47 PM.

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              • #8
                What did you get as a voltmeter reading?
                1601

                Keep eye on ball.
                Hashim Khan

                Comment


                • #9
                  36.6

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                  • #10
                    Well then, most likely the battery is substantially sulfated.
                    1601

                    Keep eye on ball.
                    Hashim Khan

                    Comment


                    • #11
                      But it was only charged to 36v so to really know I'll have to put a 48v charge to it. Can you take the cells apart & desulfate them?

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                      • #12
                        What will be interesting is whether you can get the pack voltage back up. I don't know what the cell configuration is, but if you can access it at 6 cell, or 12 volt intervals you can use an ordinary battery charger. Those are probably 100 ah cells at minimum, maybe much more than that, so something around say 10 or 20 amps would be a tickle, and should bring the voltage back up to nominal- if that's going to happen. Give each section about the same amount of time until each has been tickled up to the nominal voltage. Fully charged that pack should reach about 55 volts or so. It will be best if you can tease it for awhile to get the pack voltage up to at least 48 volts before applying the standard rate of charge for it.

                        Can you use the existing charger- depends on whether the secondary voltage is above about 60 volts or so, before the regulation circuit. If it's not that high, then no you can't. But I'm not sure of what the charger does with the secondary voltage- it could be rectified and maybe filtered, but your voltmeter reading may not show the full value of the voltage unless it's filtered. There could perhaps be enough voltage to allow it to be readjusted for the 48 volt pack.

                        Depending on the configuration you may be able to access each cell terminal and thus determine what voltage each cell is at. You might find that some are at zero volts, potentially shorted. If it were me, I'd be trying to get each cell to come up to more than a volt and maybe up to two volts before applying a charge to the pack as a whole, or in sections if that works for you. Sometimes a capacitor discharge can shock a dead cell into becoming chargeable.
                        Last edited by darryl; 01-24-2016, 07:56 PM.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                        Comment


                        • #13
                          Originally posted by darryl View Post
                          What will be interesting is whether you can get the pack voltage back up. I don't know what the cell configuration is, but if you can access it at 6 cell, or 12 volt intervals you can use an ordinary battery charger. Those are probably 100 ah cells or something like that, so something between a trickle charge and say 10 amps should bring the voltage back up to nominal- if that's going to happen. Give each section about the same amount of time until each has been tickled up to the nominal voltage. Fully charged that pack should reach about 55 volts or so. It will be best if you can tease it for awhile to get the pack voltage up to at least 48 volts before applying the standard rate of charge for it.

                          Can you use the existing charger- depends on whether the secondary voltage is above about 60 volts or so, before the regulation circuit. If it's not that high, then no you can't. But I'm not sure of what the charger does with the secondary voltage- it could be rectified and maybe filtered, but your voltmeter reading may not show the full value of the voltage unless it's filtered. There could perhaps be enough voltage to allow it to be readjusted for the 48 volt pack.

                          Depending on the configuration you may be able to access each cell terminal and thus determine what voltage each cell is at. You might find that some are at zero volts, potentially shorted. If it were me, I'd be trying to get each cell to come up to more than a volt and maybe up to two volts before applying a charge to the pack as a whole, or in sections if that works for you. Sometimes a capacitor discharge can shock a dead cell into becoming chargeable.
                          A lot of IFs. The great part is I can buy it for the scrap value of the battery & it looks & runs great, has great components & could be parted but I don't know how long it will run on a charge & I don't have room for it & still have a bunch to pickup from "the buy".

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                          • #14
                            Is it possible that the battery pack is actually 36V nominal? 36 volts on a 48V pack is about 9 volts for a 12V battery, and that is essentially dead.

                            Here is some good information on lead-acid batteries and charging:
                            http://www.evdl.org/pages/hartcharge.html

                            http://batteryuniversity.com/learn/a...d_acid_battery

                            http://www.mpoweruk.com/chargers.htm

                            http://www.mpoweruk.com/life.htm

                            http://www.mpoweruk.com/soc.htm

                            That last link shows a fully discharged 12V battery has an open circuit voltage of about 11.5V.



                            So, I don't think it is possible for a 48 VDC lead-acid battery pack, charged to 36 volts, to be able to operate a fork lift (even a toy!) There are other possibilities:

                            1. One or more of the batteries (or cells) is totally shorted or bypassed, so that only 36V of battery are used.
                            2. The cells are some other chemistry, with a nominal 1.5-1.7 vpc, such as Nickel-Zinc.
                            http://pauleschoen.com/pix/PM08_P76_P54.png
                            Paul , P S Technology, Inc. and MrTibbs
                            USA Maryland 21030

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                            • #15
                              Originally posted by flylo View Post
                              A lot of IFs. The great part is I can buy it for the scrap value of the battery & it looks & runs great, has great components & could be parted but I don't know how long it will run on a charge & I don't have room for it & still have a bunch to pickup from "the buy".
                              the voltage you read with a meter is the E effective or average , if you multiply 36 x 1.414 you will get the peak of the ac cycle and that should be 50.9 volts then take 3 phase 120 degrees apart and you almost have no ripple. full wave rectification of 60 cycles give 120 positive pulses , 3 phase would give you 360 pulses at 50.9 volts. You should read a lot higher voltage with 3 phase rectification than with 1 phase. Unless like Jtiers said it is wired to give 38 volts out with 3 phase in. 5o.9 volts would be like a trickle charger on a 48 volt battery. that's what I think anyway wish I could help you more. Jim

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