I suspect that I have cells with dendrils in my three DeWALT DE9074 12V
1.3Ah Nicad packs. These packs have been used with a DeWALT screwdriver and recharged no more than 50 times. Now the DeWALTcharger is indicating faulty battery and will not start the charge. If any of you have checked the price of replacement DeWALT batteries you will understand why I am trying to repair them.
After opening the pack I measured the voltage and current in each of the ten cells. Voltage is only m.v. +ve and current 8 microamp which is expected as the packs have been idle for 6 months.
Next I connected a "2V 0.5A" simple charger to one of the bad cells. Charging readings at switch on were 0.638V and 1.11A. After 1 hour the readings were 0.577V and 1.03A. There was no rise in cell temperature.
I disconnected the charger and could not measure any voltage or any current in the "charged cell"
Why is there a charging voltage and current but no measurable output? Is this a symptom of dendrils?
There are companies that rebuild batteries. This could be extremely handy for folks who own older tools where batteries can no longer be bought new.
You seem to be handy with this stuff, so you'd probably save time and money rebuilding your own. A quick Google search turned up:
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I haven't personally dealt with this company before, so I can't vouch for them, but there are more out there. Many stores sell standard sized rechargeable batteries, including sub-C types, with tabs already soldered in place (highly recommend!) which are intended for battery packs such as yours.
You might be able to bring individual cells back to life, as long as there's no damage from reversed voltage, which is quite possible if they've been sitting around for a long time without being used. Connecting to a slow dumb charger for a time might do it. I've had some success doing this, but the batteries never seem to last for long.
If it were me, I'd just rebuild the pack. You will most likely get better quality batteries.
As if there WERE such a thing as a "better quality" NiCad battery! Your first mistake was buying something that used nicads in the first place! The person who "invented" nicad batteries needs his/her ass kicked from here to China. They are total pieces of crap and should be avoided/replaced/ substituted/ trashed if at all possible. They are the reason my wireless phone is sitting over there unused. I just keep putting new batteries in my electric screwdriver to keep it going. Of course I don't use it much so you seem to get about 3-4 screw jobs per battery set. Nicads are the screw job!
But once you are locked into the loop. Just keep buying new batteries and putting them in! Happy soldering. Compare to my Toro battery weed whacker with lead gel cells. Got it for about $5 at a garage sale 15 years ago and it's still going strong. Yeah, gel cells die too, but at least they have some lifetime.
I'm afraid you've been seriously misinformed. Nickle cadmium batteries are just dandy, when they're used in the proper devices. They can supply plenty of amps without shortening their life, and even if abused, they can last for years. This is why they're used in high power devices, such as two way radios, power tools, and high-end flashlights.
My cordless phone is doing just fine after nearly 5 years. The batteries last about half as long as they used to, but with the use my wife puts on them, it's still impressive. They're still mostly used in police radios and flashlights, two things that, 99% of the time, are much more important than the gun they carry.
Nearly all cordless tools use them. The batteries get beat up constantly, and when a tool goes down contractors lose money, so if there was a problem with these batteries, nobody would buy them.
There was a move to change two-way radio and cordless tool batteries over to nickel hydride, but these new 'wonder batteries' really did suck. They didn't hold a charge for long, and they didn't like coughing up the amps. The newer lithium ion batteries have finally come to a point where they can deliver the power for tools and radios, but it's harder to tell when they start to fizzle, so many folks still don't trust them. Then there's the whole flammable/explosive issue associated with lithium.
There's a weedwacker at work that's still chugging along after about 8 years, and it, too, has a nicad.
I admit, it can be a crapshoot. Some corporations put the cheapest crappiest batteries in their devices. Sometimes they last for years, sometimes they don't. Many, if not most folks who sell individual cells, or rebuild battery packs, use the best they can find. Same goes with quality tool manufacturers, such as Dewalt and Bosch.
I'm surprised you have an SLA that's lasted that long. They usually go in about five to ten years. Sounds like you lucked out.
You must be doing something wrong. Mine (NiCds and NiMhs) last for years and years. I suspect you are not using them on a regular basis and charging them properly.
I have several Makita battery powered tools and in response to the above, I will state that I have gone through two sets of the new and improved nickle metal hydride batteries during which time the original USED set of nickle cadmium just keep on chugging along. I have periodically run the ni-cads down to near zero with a flashlight and that keeps them rejuvenated. I know many people dispute this, including Makita. I say it works based on experience. That and never using one until it is fully recharged have kept some of my batteries in (hard) service for over 8 years.
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