Simple Batter Monitor Works With Higher Battery Voltages

Battery-operated equipment often requires a low-voltage monitor to warn the user when the battery voltage is too low or to perform other functions, such as power-source switching or device shutdown. Many specialized ICs are available to satisfy this need, but most target applications that use fairly low-voltage lithium or NiCd batteries. Thus, they're not directly compatible with applications using lead-acid batteries, which may go as high as 14 V during charge. If you need only a simple logic-level change in response to a low-voltage condition, you don't have to overpower the design with sophisticated battery-management circuits. A comparator and a few additional parts can do the job instead.