Has anyone tried "resurrecting" Nicad batteries?

[TheFantod]

I'm on my second set of Craftsman Sears/Light combos. It's just a cordless drill with a light, and it comes with two 14.4 volt nicad battery packs.

They last about 3 years, then the batteries stop holding a charge. The ones I have now will hold a charge for about 30 minutes.

New batteries cost about $45 a pop. You can usually get a brand new set with drill & light for $39 around Christmas.

I found this site a couple of years back, and I'm a bit leery of it:
http://www.batteryresurrection.com/

From what I've read in other forums, you simply take the battery pack apart, super-charge the battery with a power source for like, 1 second, then put them back together. It's something about breaking the "memory" of the NICAD. Sounds sketchy/dangerous to me.

Opinions?

[jp58]

Originally Posted by TheFantod

I'm on my second set of Craftsman Sears/Light combos. It's just a cordless drill with a light, and it comes with two 14.4 volt nicad battery packs.

They last about 3 years, then the batteries stop holding a charge. The ones I have now will hold a charge for about 30 minutes.

New batteries cost about $45 a pop. You can usually get a brand new set with drill & light for $39 around Christmas.

I found this site a couple of years back, and I'm a bit leery of it:
http://www.batteryresurrection.com/

From what I've read in other forums, you simply take the battery pack apart, super-charge the battery with a power source for like, 1 second, then put them back together. It's something about breaking the "memory" of the NICAD. Sounds sketchy/dangerous to me.

Opinions?

That seems like a terrible idea. Batteries don't have a "memory" anyways, they have banks of chemicals that react and produce electricity through a complicated exothermic reaction.You aren't adding chemicals to the to the battery so you aren't "refilling" anything. Even rechargeable batteries die over time due to various things. Its one of those terrible facts of life: Nothing is perpetual and energy can't be free.

[jp58]

However, if you want to tape yourself shocking yourself, feel free to share the results with us.

[Bob Lee (QSC)]

I know of a Ni-Cd rejuvenation technique that you do on individual cells. It involves first charging a large electrolytic cap to about 15V DC through a resistor (to limit the inrush current) and then discharging it across the cell. The idea is that the spike of current will burn away the crystals or whatever that develop over time and short the anode and cathode together.

I tried it about 20 some years ago on some AA cells that no longer held a charge and succeeded in getting maybe half of them to work again. Most required several jolts.

I haven't tried it yet on my dead Craftsman battery packs yet. It's really frustrating that they go bad after only a couple years, by which time they're not only out of warranty but also no longer match the battery packs in the Craftsman line.

[MadMan118]

I have a Makita drill that's about 7 years old never had to replace a battery yet. My advice go buy a makita. Ive never had a craftsman tool I've liked.

[L-A]

Originally Posted by MadMan118

I have a Makita drill that's about 7 years old never had to replace a battery yet. My advice go buy a makita. Ive never had a craftsman tool I've liked.

Makitas are the electrician's best friend. They're ligther than most, and hold a charge longer, but that's because they have a weaker wattage compared to their direct competitors. It's not like you use drills and screwdrivers on full throttle anyway.

[Bob Lee (QSC)]

It's been many years since I've tried this, so some details are fuzzy in my brain. Here's a basic NiCd zapper for resurrecting cells that have shorted internally.



The resistor would be around 2 to 5 kΩ (the specific value is not critical; it's just to limit the charge current into the cap). The cap would be probably around 2000 µF (also not critical) with a WVDC greater than the DC voltage applied. Experiment with the cap value; too small might not provide enough energy to zap the short, and choosing one vastly too large might zap the cell too aggressively and cause additional damage to the it.

Move the switch to "charge" to charge the cap. The voltmeter will show the charged voltage. It should charge very quickly, almost instantaneously in terms of human perception.

Move the switch to zap to discharge the cap through the NiCd cell. If the short clears, the cell will begin to show a noticeable residual voltage on the meter. A cell might require repeated zaps to fully clear the short.

If you can clear the shorts of all the dead cells, the pack can then be charged.

[Rune Bivrin]

Originally Posted by Bob Lee (QSC)

The resistor would be around 2 to 5 kΩ (the specific value is not critical; it's just to limit the charge current into the cap). The cap would be probably around 2000 µF
[...]
Move the switch to "charge" to charge the cap. The voltmeter will show the charged voltage. It should charge very quickly, almost instantaneously in terms of human perception.

Just to note that with the values given the time constant of the circuit is 10 seconds. While I'm not the best time keeper in the band even I wouldn't perceive that as instantaneous

I'd go for somewhere around 20-50 ohms rated at 5 watts.

[Bob Lee (QSC)]

Originally Posted by Rune Bivrin

Just to note that with the values given the time constant of the circuit is 10 seconds. While I'm not the best time keeper in the band even I wouldn't perceive that as instantaneous

I'd go for somewhere around 20-50 ohms rated at 5 watts.

Hah! Yeah, you're right. I messed up an exponent or something punching it into the calculator. Thanks for catching that!