The Black and Decker is a cordless household drill that can be found by the serial no. LDX 120C

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Black and Decker 20 volt Battery wont charge

I have 2 Black & Decker 20 volt "Matrix" batteries.

During another household project, I used the battery as a power supply for something else. Low draw, was not getting hot. Discharged down to 17 volts. Now when I plug it in, charger just shows "bad battery".

Another just shows "bad battery" on the charger when I plug it in. It's practically new but I have no insight on that one.

Anyone familiar with how these opperate that might have a fix at least for the first one? My suspision is that somehow the battery knows it was used for something it should not have been. If that's the case...can it be reset?

Same problem with older 18 volt "Firestorm" battery. This could be age...but every battery (3) shows bad?

Answer this question I have this problem too

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Jason Cox do you have a model number for either the battery or the drill/driver itself?

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1 Answer

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Hi Jason. Sometimes you can revive a "bad battery" by manually charging the battery with a variable voltage power supply. In this case you have a 18.5v battery which is operating at 17v. You know that the battery pack is composed of at least (5) 18650 lithium ion cells in series. Voltage adds in series. 18650 cells have a nominal voltage of 3.7v (3.7*5 = 18.5v). Most 18650 cells have a charging voltage of 4.2v. If you charge the pack at 21v (4.2*5=21) or just slightly higher (~21.5v), you should be able to boost the nominal voltage of the pack closer to the desired 18.5v. I have found that manually charging a "bad battery" with a variable power supply for 10-15min will bring up the pack to a level where the genuine drill power supplies will be able to recognize and charge the battery pack again.

Good luck.

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