12v plug in car battery and charging system tester, test battery condition & alternator charging (lcd display) tn tonny tonny 12v car battery monitor, it shows very clear the status of your car's battery, it protects the engine computer and 12-volt accessories from damaging surges when jump starting or recharging. the lcd screen displays the measured voltage with a bar graph to indicate battery charge level quickly identify the battery's charge status.<br><br><b>parts diagram :</b><br><b>pivoting head</b> - pivots for easy viewing and angle adjustment<br><b>voltage reading</b>- refer to battery state of charge chart for voltage reading levels<br><b>charge graph</b> - displays the measured voltage to indicate battery charge level <br><b>red led</b> - indicates bad test result<br>alternator test :15.11-16v <br>battery test : 11.99 - 0v<br><b>yellow led</b> – indicates potential problem or low voltage <br>alternator test : 14.51 - 15.1v<br>battery test : 12.00 - 12.60v <br><b>green led</b> - indicates good test result <br>alternator test : 13.51v -14.5v <br> battery test : 12.61 - 13.5v