Is the battery empty, or is there something wrong with the device? That’s always a difficult question when your walkman or some other battery-powered device appears to be dead when you switch it on.

This circuit runs a fast battery test without the need of power supply or expensive moving-coil voltmeters. It features two ranges: when SW1 is set as shown in the circuit diagram, the device can test ...

Numerous gadgets, from remote controls to hearing aids, depend on small batteries. It’s vital to know when these batteries are close to being drained so they can be substituted before they’re fully ...