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Battery Troubleshooting

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    Battery Troubleshooting

    Is it your charger or your battery?

    First step is to test your charger. Make sure your charger is working properly. Having an extra charger around can make this step a snap...if you don't have an extra charger around consider buying one. The charger is usually the culprit not the battery and it’s good to have a back up. (see future article on troubleshooting your charger)
    What is the volt reading of your battery?
    Get a volt reading of the battery. If your battery is reading 0 volts….more than likely your BMS has shut down all power to the pack.
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    Is the BMS your problem?

    The BMS is the protection system that keeps your battery safe (read the article on BMS)
    Unfortunately sometimes an overzealous BMS can keep an otherwise good pack from working. More often than not in a failed pack it is a bad BMS.
    For example many BMS’s have a short circuit protection….if they detect a short they shut down the pack and the BMS can sometimes not be reset so easily.
    One typical thing that can happen with a high amperage battery is plugging in the battery or even switching on the wrong kind of on/off switch can trigger a spark which the BMS reads as a short and instantly shuts down.
    To avoid this use xt90s spark resistor connectors when plugging in your battery.
    If your BMS has shut down the pack, the first thing is to try charging the pack. If this does not jolt the BMS more extreme measures are needed.

    Jump starting your BMS

    Sometimes to reset a BMS requires charging through the discharge wires for a few seconds to jolt the BMS back to normal mode. After charging for a few seconds from the lead wires try charging now through the normal charge wire and see if the pack charges normally now.
    If it charges OK, now try it on the bike and make sure it discharges OK.
    NOTE: It is important that you do not use the discharge wires to charge your battery for more than a few minutes because you will have no BMS protection if you do so.
    You can see a guide on how to do this with a dolphin type pack here.

    Check your connectors

    One easy thing to check before taking on disassembling your battery is your connectors. If you battery is not taking a charge be sure to check the charge connector on both your battery and charger and see if it has any damage. Same with the discharge wires if your bike is not putting out power.

    If you comfortable with a solder gun and you are in doubt, you could try replacing your connectors.
    If these steps do not work in fixing your battery, it is time to take more drastic steps which involve disassembling your battery.
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    Disassembling your Battery

    Note that lithium packs contain a large amount of energy and can discharge it in a dangerously short period of time resulting a shock or fire. (see Kentucky Fried Fingers below) If you are not completely comfortable working on large battery arrays contact us for further direction.
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    Disassembling your battery is not as hard as it sounds especially if you have a hard pack such as a shark or dolphin pack.
    Just undo the screws and you should be able to have your pack taken apart in a few minutes.
    If you have a soft shrink wrapped battery you are going to have to cut open the shrink wrap. This is easy to do but re-shrink wrapping your pack is a lot more work and you may want to just settle on duct taping it instead which works just as good but does not look as nice and is not as waterproof.

    What to look for once your pack is disassembled?
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    First thing to look for is physical damage. Do you see burn marks by any of the cells.
    Are all the wires intact? Many times you can see a loose wire...and that is probably the culprit. Track all the wires that you can, the best that you can and make sure they are soldered into place.
    Is the balance wire plug plugged in solidly.
    All our BMS’s have a white connector that plug into the board on the BMS. Sometimes this plug can wiggle loose. Make sure it is plugged in firmly.
    If none of this resurrects your pack its time for some real fun.

    Reset the balance connector
    Unplug that large white balance connector ….wait a minute and then plug it back in. This sometimes will reset a BMS that jump starting has failed on.

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    Checking all your cell banks using a volt meter on the Balance connector
    (we will be providing pictorial or video soon on how to do this)

    Unplug the white connector and use a volt meter to check the voltage of each cell bank. These should all measure more or less the same. IF you have one or 2 banks of cells that are measuring more than half a volt lower than the rest of the banks… have some bad cells and this is your problem.
    If all the cell banks read more or less the same, and you have troubleshot all else effectively, then it is pretty much a sure thing your BMS is bad and needs to be replaced.

    Here is a link to our video showing how to test a BMS and your cell banks.

    If you have bad cell banks
    This is very bad news and is a rare occurrence. This happens usually from dropping the pack and damaging a cell or the spot welds that hold the cells together.

    Many times it is caused by a bad BMS that takes down a row or two of cells with it.

    Trying to fix a pack with bad rows of cells is for advanced users only, and if you bought your pack from Luna Cycle now is a good time to consider having them do the repair.

    If the cell bank in question is not too low you can try to resurrect it using a low voltage charger and get it up to the level of the rest of the banks. You would also want to replace the BMS because now the BMS is suspect.

    If the cell bank is very low (under 2 volts) this bank can never be safely resurrected and you should not even try.

    If you have bad cell banks that cannot be saved it is a good time to give up on the pack....or go through the nightmare job of disassembling the pack and trying to salvage the good cells or replace the bad cells using a spot welder.

    Replacing your Bad BMS

    The BMS is not very hard to replace if you can get the same exact BMS your pack was constructed with so the Balance connector matches up.
    You can get a matching replacement BMS very easily for a Luna Cycle pack if you bought your pack from us.
    You then only have 4 wires that needed to soldered onto the BMS (a positive and negative for both the discharging port and the charging port). This is an easy and quick job and is a good introduction to soldering if you have not done it before.
    We will be doing article video soon on how to replace your BMS
    Original article by @EricLuna ,
    Attached Files
    Last edited by Bicycle365; 10-19-2016, 10:37 AM.