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  1. #1
    RC Enthusiast
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    Lipo charging problems.

    I have two dynamite 5300maH 25c 2s lipos for a 14.4V dewalt E Maxx. I haven't drained both of the batteries beyond 80%. To charge the batteries I use the passport ultra Ac/Dc. One of the batteries will get unbalanced while charging, sometimes by as much as 300mv. While the battery is charging, the main screen displays 8.40v, but the individual cell voltages do not add up to 8.4V. For example: S1 will be 4.185V and S2 will be 4.026V, But the main screen will display 8.40V. If I stop the charging, and unplug the battery, then plug it back in, and start charging, the voltages will be correct, and the unbalance voltage is lower too. If I chose to balance charge, the charger will let the battery get unbalanced by as much as it wants to be, while it is supposed to prevent that as soon as the battery reaches 20mv. The other battery will not do this as much. What kind of problem is this???

  2. #2
    RC Champion
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    First do you use the balance setting on your charger if it has one? You should always balance lipos, it takes longer but in the long run it can prevent damage to the cells if they become unbalanced.
    Nothin' like a 4 on the floor and a V8

  3. #3
    RC Turnbuckle Jr.
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    Are you connecting both the main power leads and the small white/ black balance connector with 3 small wires coming from it to the lipo? Those both need to be plugged in whilst using the balance-charge mode.

    You should be setting the charge current to 5.3amps or as close as possible without going over ( 5amps say ), which should result in a ~1 hour charge time- no need to stop the charge and restart it, let the charger do it's thing and check the cell voltages every so often.

    Sounds like the main screen is displaying the fully charged voltage/ setting, not the actual total voltages, so ignore that. And what do you mean ( 'flash gordon approaching'?... ) by 20mv exactly? Lipo chargers dont peak lipo cells, they simply force current into them until they wont take any more without going over 4.2v per cell, at which point the charge is over and the charger should beep to tell you. Once a lipo is charged it stays charged for months and months without losing hardly any voltage at all ( ~0.03v after 3 or 4 months in my testing )...
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  4. #4
    RC Enthusiast
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    Every thing is connected and set properly. In the manual of the charger, it said that in balance charge mode, if the lipo goes over 20mv unbalanced the charger will stop charging and balance out the cells within 10mv then resume charging. I recently stopped the charging of that lipo, with unbalance of 48mv (read from the charger). I returned back after a few hours and put it back on charge, the unbalance voltage read 4mv... Last time I put this battery on balance charge, it timed out my charger at 100 minutes. My other lipo never gets over 10mv unbalanced.

  5. #5
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    Are you able to override the "time out"? My charger has such a setting, but I always turn it off. Sometimes my packs take forever to charge, like 180 minutes or more - this is usually if my packs have been in storage charge, and then I top them up before I go use them. I don't know why it would take so long to put a small amount of charge in it - no doubt it's a complicated calculation but I can't be bothered finding out why. If you use the storage setting it will put about 80% charge in them. This is the best way to store them long term.

    If I use my packs fully until the lipo cutoff in the ESC, the packs take about 70 minutes to fully recharge using the balance mode (with time out turned off).

    I would advise you turn off the time limit, go use the packs properly until they hit low voltage cutoff and then go charge them. Batteries need to be cycled (at the very least) every once in a while.
    You are unique just like everyone else

  6. #6
    RC Turnbuckle Jr.
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    Hmm, sounds rather like a couple of mismatched cells in a pack together, I would also say to raise the safety time-out limit and give the charger longer to do it's thing; so long as the cells dont overcharge then thats the important factor.
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  7. #7
    Marshal Dadx2mj's Avatar
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    What kind of problem is this???
    This is the kind of problem that should be addressed to the battery or charger manufactuer or vendor. Traxxas does not allow this kind of tech support of other companies products on this forum.
    BlindMan Racing
    Rusty - MERV - Pede 4x4-Alias
    SPC Lipo Power

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