rebuilding cordless drill batteries

[David Gretzmier]

I was thinking of rebuilding my black and decker 18 volt battery with 5 18650 tenergy 2700 mah cells. I notice you can buy 18650 packs in various voltages and mah, so it seems as though this is safe. has anyone here ever done this, and will the original charger work? there are 15 nicad cells in there now, around 1.4 amp hours, and it tests anywhere from 20.5 freshly charged to 15 completely dead. since my 18650 cells for my flashlight are 4.2 right off the charger, 5 3.7 volt cells will be 21volts at maximum charge and 15 volts low end max ( drill won't run ) will put the cells at 3 volts. will the protection circuit in the cells still work if these are soldered together?

 

[Black Rose]

Highly doubtful that the NiCd charger would be able to charge the 18650 Li-Ion cells.

 

[David Gretzmier]

The charger is putting out between 21 and 22 volts. are these volts different than 4.3 volts the charger I use to charge my 18650's now? I know there are different amp loads given to those volts, and that affects how fast the cells will reach a full charge, but is there another force at work?

 

[paulr]

To recharge lithium batteries safely you need a charger intended for that purpose. You are risking serious explosions and fires if you do what you're describing. See various photos of explosion results in old threads here, and in RC modelling forums. You're better off using sub-C NiMH cells. The original charger won't be optimal in terms of cell longevity (it won't detect charge termination correctly) but shouldn't create such a hazard as with lithium cells. You could use an RC charger like a Triton but after all the expense and hassle you might as well just buy yourself a better drill.

 

[David Gretzmier]

I could easily use sub-c cells, the nicad run around 2400mah and are 1.60 apiece on ebay. nimh are about double that for 3800-4500mah. I'd need 15. I wanted to make an awesome battery for aound 35 bucks, and at maximum capacity. The best nimh's out there would actually last longer than the 18650's on a per time basis, but lithium will take many more charges. I just see these lithium ion drill batteries out there with a 2.4 amp hour rating and they cost 90-100 bucks. I can make my own for 35 bucks using 18650's, so why not? It seems the protection circuit on each cell would shut it down before it overcharges or overdischarges. The cells I've seen explode on youtube were unprotected and heavily overdischarged.

 

[MarNav1]

Check out All-Battery.com.

 

[radiomanss]

David,

I know this is a very late reply -- just came on your post while browsing.

But I have replaced the innards of a battery pack (on a superb Bosch drill). I chose to use exact replacement, but with higher capacity: sub-C nimh. The biggest pain was soldering the cells together (bought them with tabs, from Mouser), and squeezing the finished assembly into the original battery holder.

Results: outstanding. Cost: about $35.

Send me a note if you want further particulars.

Stanley

 

[Big_Bayou_Hooter]

Send it to voltmanbatteries.com and he will rebuild any battery you can think of. I had a Hilti 36 volt hammer drill battery that went bad and a new one was $360. Voltman rebuilt it for $75 and it was better than a new one.