Nickel–cadmium batteries can be an economical (and environmentally beneficial) alternative to conventional cells . . . if you get their full life.
Building a Nicad Battery Reconditioning Machine
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 MOTHER EARTH NEWS 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 and — presumably — 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.
Nicad Battery Reconditioning 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 life–threatening shock! For safety's sake, please follow the directions carefully, and use only a plastic case.
The Healing Battery Machine
The nicad resuscitator can be used to resurrect batteries up to 22 volts in capacity. With the line cord unplugged, connect the red and black clip leads, respectively, to the positive and negative terminals of the faulty battery. (You may need to use a specific type of connector, such as a battery holder, to attach some batteries.)
Insert the plug into an outlet and wait until the READY lamp lights. This should take about 90 seconds. Now press the RESTORE button. The READY light should go out. If not, check your battery connections.
It may take several cycles to completely "cure" the battery, so continue the procedure until the battery accepts a full charge under normal charging conditions. Be sure to allow sufficient time for the READY light to come back on before you push the RESTORE button again. When you're done, always unplug the AC cord before disconnecting the battery leads, and always leave the cord unplugged when the unit is not in use.
Not all nicads can be restored by this method — even under optimum conditions, there are limits to their lifespans — but most can. In a few cases, the battery's capacity will only be partially restored. But even then, some is better than none. And you may find that many batteries will return for another half (or more) of a lifetime.