Jump starting a lithium-ion tool battery.

[WildwoodChuck]

Thursday morning 12/27/18 I bought a display DeWalt 12v Max 1/4" hex impact with battery for 50 bucks at a local hardware store. I had 2 DeWalt 12v/20v chargers at the house and I need smaller tools for the helpers at home that struggle with the 18v Ryobi tools I have so I took a chance and bought it. I tried the battery on both chargers and got nowhere. Thursday night I watched a couple youtube videos about quick fixes.

Last night after 6 I got out my voltmeter and checked continuity and voltage on the DeWalt 12v max battery (1.2v) and a 12v Milwaukee battery (12.3v). I used 2 sections of wire about 12” long. I touched the positive to positive and neutral to neutral for about 1 second. DeWalt battery was at 2.7v and put it in the charger, no activity lights on the charger. I touched the contacts a second time for about 3 seconds and that brought the DeWalt battery to 6.5v, put it in the charger and I got charge activity lights on the charger. After about 10 minutes I got a hot battery indication. I took the battery off the charger for 30 minutes or so then put it back in the charger. In less than an hour I had charge complete indicator on the charger. I tried the battery on the impact and the impact would go in forward and reverse like it should. All the steps happened just like the youtube video stated. 2 short jumps, hot pack, fully charge like normal.

I will test the battery over the next few days with some household projects to see how the battery cycles. I have no experience with a DeWalt 12v max impact and I don’t have a second battery to use for comparison so all I will be able to tell is if it runs down really fast or after only a few screws.

 

[Old Man Roger]

I've seen shorting save a nicad but never a lipo?
I've had luck jump charging a dead lipo using the nicad setting on my multi charger. My charger wont start charging a lipo if the batteries voltage is too low, the nicad setting will. Lipos charge at a much lower amp setting than a nicad so I just do it till the voltage is high enough to start the lipo setting.

Disclaimer Shorting or charging a lipo at a higher than recommended setting is dangerous and can cause the battery to explode.

 

[rsanter]

I belive the warranty starts from time of purchase.
Go haventhem replace the battery

 

[WildwoodChuck]

I would agree about the warranty had I bought it new and not bought the display model at a reduced price.

 

[Two Speed]

I've seen shorting save a nicad but never a lipo?

Hi Didn't short the dewalt, he hit the dewalt with 12 volts from a good battery, just like putting two car batteries in parallel to "trick" a smart charger into charging.

 

[MattT]

I've seen shorting save a nicad but never a lipo?
I've had luck jump charging a dead lipo using the nicad setting on my multi charger. My charger wont start charging a lipo if the batteries voltage is too low, the nicad setting will. Lipos charge at a much lower amp setting than a nicad so I just do it till the voltage is high enough to start the lipo setting.

Disclaimer Shorting or charging a lipo at a higher than recommended setting is dangerous and can cause the battery to explode.

I'm guessing it was high risk rapid charging to get enough voltage into the pack so the charger would recognize it rather than "shorting". Could do the same thing much safer using something current limited.