Question About Ni-Cad Battery

[radar696]

I have an 18v cordless drill that came with 2 Ni-Cad battery packs.

It isn't that old but one of the battery packs has quit taking a charge. I'm betting it's because it just doesn't get used on a consistent basis.

Is it possible to shock this battery back into life? I have read somewhere that you can do this with Ni-Cad based batteries at times.

I understand the dangers of things like this going bad and am prepared to take the proper precautions if I did attempt this.

Also I apologize since this is not a flashlight related battery.

 

[SilverFox]

Hello Radar,

One mode of failure with NiCd cells is dendrite growth that penetrates the separator and shorts the cell out internally. You can subject the cell to a momentary high voltage and blow that short off, but you end up with a cell that has a hole in the separator and another dendrite will quickly form.

It is better to take the battery pack apart, locate the bad cell, and replace it. The problem with this is that now your cells will not be balanced within the pack, and you have to take precautions to keep from driving the other cells into a reversed charge state.

The best bet is to send your pack off to a battery pack rebuilder and have them replace all the cells.

Sometimes you can revive a pack by a deep slow discharge followed by a long slow charge. You can discharge by hooking up an automobile light bulb to the pack and you can then watch the discharge. If the lamp changes brightness in flashes, it generally means that a cell is getting close to, or going into reverse charge. NiCd cells can handle this better than NiMh cells, but you still have to keep on top of this. The idea is to end up with all the cells at the same state of discharge, then to charge them and hopefully they will all charge up equally.

I have spent hours doing this, and am successful about half of the time.

Tom

 

[Fallingwater]

It would probably be better to discharge the pack cell-by-cell if using the lightbulb method (you obviously need a bulb that'll run from one cell), precisely to avoid reverse-charging cells. You do need to open up the pack for this to work, obviously...

 

[radar696]

Thanks for the responses Silverfox & Fallingwater,

I guess the part that really gets me is that one new Black & Decker battery cost about $25.00. Yet I can get a complete drill kit with 2 batteries for about $35.00 or more depending on model.

Just doesn't seem right does it.:candle:

 

[Fallingwater]

They overcharge the spares because most people will buy them anyway.

The few, the proud, the DIY re-cellers, do not have this problem.

 

[Yoda4561]

Also be aware that running the pack down with the drill to the point where it won't even spin the chuck anymore is NOT good for the cells. I'd charge the pack up and use it hard, not so hard that it overheats though, and charge it up as soon as the drill starts to loose torque. Hopefully after a few charges it'll be all good. I had a ryobi drill that did that after 2 or 3 charges and didn't get much better, I switched to bosch cordless and their bluecore batteries, still performing like new 2 years later. I think part of it is their charger is better, and the bluecore batteries have heatsinks between the cells to help prevent pack overheating.

 

[Eugene]

Thanks for the responses Silverfox & Fallingwater,

I guess the part that really gets me is that one new Black & Decker battery cost about $25.00. Yet I can get a complete drill kit with 2 batteries for about $35.00 or more depending on model.

Just doesn't seem right does it.:candle:

Thats the way it is with a lot of them. Go to ebay and search for dewalt, makita, etc and you'll find a bunch of drills without batteries where people have bought the kit and then ebay'ed the drill and kept the batteries.

My old Makita 9.6v the batteries used to sell for $30 and it was around 25 or so just to buy the internal nicad cells so I just bought new packs. I did keep the old ones though because now the packs are up around $38 so I could order and rebuild the older packs for cheaper.