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Old 12-17-12, 07:51 PM   #13
Ryland
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Quote:
Originally Posted by Mikesolar View Post
I'm looking for a DIY idea to rehabilitate the dead lithium batteries. It can be done with other types and I just had 2 of my Makita batteries croak on me and they were not old.
I've had the compact lithium Makita batteries "die", same with the DeWalts... the cells are still just fine but the battery drops in to a fail safe mode, on the Makita that happens if you try to run the battery 100% dead, for example you are screwing in a screw and it starts turning slowly, you keep going, the drill stops and you keep forcing that screw in that last half inch, you then take the battery off the tool and put it on the charger, the broken battery light comes on, sometimes you can connect a full battery to the dead battery for a few minutes and get enough power in it that the charger will recognize it and charge it but a lot of the time it's the battery management system that is built in to the battery that has tripped and is sending a signal to the charger saying that one or more cells in the pack were drawn down and might now be damaged/a fire hazard and that it should not be charged.

On DeWalt batteries this will happen if you are doing something like powering an electric bike and you only have a single pack on the bike, then switch on the speed controller without a pre-charge resister, the sudden load from the speed controller can be more then the fast blow fuse in the BMS can handle, that fuse is sealed in epoxy, in the BMS, solution to this is not to put a huge load that makes the battery think it's being shorted out.

You can still charge these "dead" batteries, but the BMS will tell the charger that they are not safe to charge, so charging them is best done off of another battery or in parallel with another battery, that is how I charge the mass of lithium battery cells for my lawn mower, I plug the block of cells in to the charger then plug a regular lithium battery in to the charger to make the charger turn on.

If used normally I've never had a battery fail.

Last edited by Ryland; 12-17-12 at 08:00 PM..
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