What's the best way to keep batteries charged?

Our sons have given me a number of cordless tools, but when I want to use one of them, the batteries soon run low because they've lost their charge sitting on a shelf. Is there a way I could plug the chargers into a power strip, and then plug the strip into a timer to charge the batteries, say for 30 minutes every day? Or would that harm the batteries?
—Robert Jesse, Moweaqua, Illinois

That approach is a crude version of what some tool battery chargers do automatically, Robert, and it could work if left on long enough each day to fully recharge the battery. Leaving a battery in an unplugged charger shouldn't create problems for either the battery or charger.

However, a check of your tool owner's manual may make all of this unnecessary. More-expensive cordless tools usually come with high-end features, such as chargers, like the one shown above, that bring a battery up to full charge and feed it a maintenance, or "trickle," charge as needed.

Other tool manufacturers discourage leaving batteries in unattended chargers for long periods. A charger malfunction could result in the battery going into continuous overcharge and becoming overheated. Only the owner's manual for your tools can specify whether continuous charging is right for you.