Q&A: Getting the Most From Rechargeable Batteries

I have several rechargeable batteries, and I want to make them last as long as possible. I have heard that some kinds of batteries develop a "memory" if not charged properly. Also, will overcharging them affect their lives? Some say you can't overcharge a battery, but others seem to disagree.

--Phil Lee, Pueblo, Colorado

First-generation rechargeable batteries were based on Nickel and Cadmium, and hence were known as NiCads. NiCad batteries were notorious for their "memory effect," which means that if you consistently recharged the battery at about the same point in its discharge, say, when it had 50 percent of its charge left, then it would begin to think it was completely discharged at that point and you'd end up with a battery that ran out of power way too soon after each charge.

These days, NiCad batteries have been largely replaced by NiMH (Nickel-Metal Hydride) batteries, and these don't suffer as badly from memory effects as old-fashioned NiCads once did. Like all rechargeables, though, NiMH batteries have a limited lifespan of about 500 charges or so, and they'll die more quickly if you aren't careful about your charging technique.

If you own a smart charger--which automatically shuts down when the battery is charged--you don't have to worry so much about this problem. But most less-expensive battery chargers tend to leave the battery in trickle-charge mode even after it's fully charged. That keeps the battery hot, and the heat causes the battery's internal components to break down and not work as well, eventually affecting the battery's ability to hold a charge. So if you leave your batteries in a charger for days at a time, you're taking months or years off of their life. Bottom line: It's a good idea to get them out of the charger as soon as they are charged.

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