Go to Amazon Sites : br br BatteryMole Car Battery Warning System (12 Volt Automobile Battery Monitor with Battery Failure br br Patented technology that virtually eliminates unexpected car battery failures br After the engine is off for a minimum of 4 hours engine start times all cars start voltages most cars are sampled and displayed br Calculates the batterys state of charge after the battery has been at rest for 4 hours br Performs a comparative analysis of engine start times and start voltages in order to determine the batterys health br Warns of low battery voltage charge alternator charging problems relatively slow engine start times and relatively weak start voltages