The Nicad Resuscitator

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Nickel-cadmium batteries can be an economical (and environmentally beneficial) alternative to conventional cells . . . if you get their full life.

by TJ Byers

In ten short years, rechargeable nickelcadmium batteries have become commonplace modern conveniences. They now power everything from razors to radios, and when one goes dead you simply plug it in for a recharging. (See issue 95, page 50 for instructions on building a charger.) A time comes, however, when the battery simply won't hold a charge any longer andpresumably-must be replaced.

Unfortunately, many nicads get deep-sixed before their time. In most cases, more than one cell is needed to power a device, and one bad cell can drag the rest of a perfectly good battery down. Most often, the problem is an internal short, which bypasses current around the affected cell. The other cells are actually fine, but there's not enough capacity for the job, so the battery gets thrown away.

Fortunately, on the other hand, an ailing cell can often be shocked back to life if you force enough current through it to cause the short to burn away. Once that electroshock therapy is finished, the battery can be recharged for normal operation.

CONSTRUCTION

To assemble a low-cost "nicad nudger," start by drilling holes in the plastic case and mounting the switch and the neon lamp, as indicated on the parts layout. (Use rubber cement to secure the lamp.) Then solder the components together, being careful to observe the polarity of the capacitors and the diode. Tie knots in the AC line cord and the clip leads inside the case, so that the wires won't pull on the components inside. This is particularly important with the line cord: If the uninsulated leads were to come out of the side of the case, you could get a lifethreatening shock! For safety's sake, please follow the directions carefully, and use only a plastic case.