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Lipo resurrection

  • 13-03-2013 5:15pm
    #1
    goldwing
    Registered Users, Registered Users 2 Posts: 252 ✭✭


    I have two Turnigy 5000mah 4s lipo batteries, long story short they will not charge anymore the charger tells me that the voltage is too low (how this happened is a mystery) the voltage cut off on my brushless system is set to 12 volts. I'm wondering if anyone with some experience of these batteries can some how get the voltage back up I'm not willing to do it myself as I am still learning and I am new to the lipo power side of the hobby, thanks


Comments

  • #2
    T-Maxx
    Registered Users, Registered Users 2 Posts: 3,208 ✭✭✭T-Maxx


    Unfortunately with lipo cell chemistry once a cell is gone - it's gone.

    Sometimes it happen that the cell voltage is just slightly too low to initiate charging and by bumping it over the threshold you can get it charging again. I suggest you try:

    1. Initiating charging a few times - every time you do the voltage should creep up unless it's really buggered.
    2. Check the individual cell voltages and isolate the problem cell, then charge that cell on its own (lipo s1 setting on charger).
    3. As above (2), but set the charger on nimh setting.

    Be very very careful though, lipos are potent stuff. Always use a "charge bag" or non-flammable sealing container such as a metal money box.

    If you can't revive the cell, recycle the pack, or if you're confident take the dead cell out and convert the pack to a 3s.


  • #3
    goldwing
    Registered Users, Registered Users 2 Posts: 252 ✭✭goldwing


    I have read similar things on other forums but I'm afraid to try it due to reading alot of horror stories and my lack of expierence


  • #4
    goldwing
    Registered Users, Registered Users 2 Posts: 252 ✭✭goldwing


    Ok I managed to bring one back to life the other one seems to be more than a voltage issue according to the charger it's a connection problem, is it possible that its a bad connection in side the battery I can't see because it's a hardcase.


  • #5
    T-Maxx
    Registered Users, Registered Users 2 Posts: 3,208 ✭✭✭T-Maxx


    It's possible that one of the charge lead wires is off or that the plug is dodgy, could also be that the cell voltage is so close to nil that the charger doesn't recognise the cell as being there.

    Only solution I see is to open the pack.


  • #6
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Most lipo chargers will not recognise the battery below a voltage of 3v per cell or something near that.

    I have recovered individual cells by applying a voltage matching the cell voltage as ascertained with a multimeter.

    Then with an ammeter in circuit, I gradually increase the voltage get the voltage to just above 3v, monitoring the current as I go. After that, the lipo charger can balance the cells, then charge the batter.

    If the lipo cell is below 2v or even maybe 2.5, it is likely not going to be fit to use it much, even if you recover it. The cell that dipped low will discharge more than the others, causing the same problems again.

    Once any puffing at all is seen, it is for the bin by proper procedure for lipos.


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  • #7
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    goldwing wrote: »
    Ok I managed to bring one back to life the other one seems to be more than a voltage issue according to the charger it's a connection problem, is it possible that its a bad connection in side the battery I can't see because it's a hardcase.

    It can be a connection problem with the balancing lead, with one of its wires onto a cell. But if a cell has dropped below the 3v threshold (depending on charger), it will see it as a missing cell.


  • #8
    goldwing
    Registered Users, Registered Users 2 Posts: 252 ✭✭goldwing


    Bruthal wrote: »
    It can be a connection problem with the balancing lead, with one of its wires onto a cell. But if a cell has dropped below the 3v threshold (depending on charger), it will see it as a missing cell.

    The balancing lead is fine it's working for others batteries just this one there is an issue


  • #9
    T-Maxx
    Registered Users, Registered Users 2 Posts: 3,208 ✭✭✭T-Maxx


    He means the balancing/charge lead/plug on the battery itself.


  • #10
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    goldwing wrote: »
    The balancing lead is fine it's working for others batteries just this one there is an issue



    First test the battery voltage itself anyway, which should be 14.8 or above for a 4 s. If it is sell below that, then the battery is likely for the bin.

    If it is at or above that, but the charger is giving a connection problem, then it is possibly a balance connection wire problem, as well as cells now bad if you managed to test and recover individual cells.

    Lipo batteries are very simple to understand, once you see a diagram of the balance leads with reference to the cells and main leads.


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