NiCD capacities?

I found some old NiCD batteries in an old flashlight of mine and put them through the refresh and analyze mode on my C9000. They both ended up having a capacity of approximately 750 and were within 5-10 of each other. The strange thing is that there is no capacity rating on the batteries that I can find. Compared to my NiMH batteries, the 750 capacity is pretty low, but I don't know how NiCD and NiMH compare. If my 2000 NiMH came in that low, I'd throw them out. Are these NiCD batteries worth keeping?

The low capacity NI-Cads are used chiefly for very low current applications....such as solar lights like the type used to line your walkway.

They perform very well at these types of applications because they inherently have a low self-disharge rates which helps them perform reasonably well at the low charge/disharge rates. Basically they don't self discharge faster than a small solar cell can charge them at, like a standard NiMH would.

Their low capacities tend to help the batteries go through a more complete charge dicharge cycle (critical for NI-CAD longevity). I have some 600mA and 700mA NiCd cells with 3 years of cycles (1000+) on them and they still test out at 80-90% of their rated capacites.

If they are AA, 750mah is close to the maximum you can have for LiIon. Keep them; they have rather less self-discharge than ordinary NiMH, so they can be decent substitutes for Eneloops in low power applications and/or ones where you don't need great run time.

Turak: actually, nowadays NiCD cells are used mostly in high-discharge applications, because they are very tolerant of abuse (more so than NiMH, in fact). Many cordless drills use them, and those that don't mostly jumped straight to LiIon/LiFe. But LiWhatever is expensive, so cheap drills still run on NiCD. Also, RC car enthusiasts often use NiCD packs for acceleration races, where burst discharge is more important than battery life.

Hello Bmoorhouse,

The big problem with old NiCd cells is that they sometimes develop high self discharge rates. You should charge your cells up and let them sit for a couple of days. Then do a discharge and see where they are at. If they are still showing good capacity, they should be good to use.

Tom

Ahhh...Silverfox. You bring back memories.

Good old NiCd's and the way they tend to die. Hehe....talk about self discharge...they basically develop internal shorts. Self discharge almost instantly instead of days.

I have dissected many NiCd batteries in days gone by. Typically I found that they formed internal dendrites composed of cadmium salt pathways through mircroscopic holes formed in the separations layers.

We used to take and charge up the capacitor bank of a specialized Power Supply we used for magnetizing flip-dots and discharge the bank into a shorted NiCd. It would discharge hundreds of amps of current that lasted only microseconds....and basically burn up/blow away the salt pathway...similiar to blowing a fuse. Problem was that the salt trace would always reform in the same spot in a short period of time.

We have some 850 mAH AAs that we got from CCrane long ago that still give good service. Mostly we use them in Motorola two-way radios which we use every day. Mrs Umbra used them for a few weeks in some new body mics recently and they worked very well in that application. Even though I'm a NiCD fan I was kind of blown away by how well those old cells performed.