Compact size and easy to operate. Just connect the clamps to the positive and negative terminals of the battery you need to test, and you can start using it LED shows the battery status, green light Full means the battery power is full. Yellow Middle indicates medium battery level. Red Low means the battery is low and needs to be charged You can detect whether the battery charging is in normal status. Red Fault means charging is not normal, and green Good means charging is normal. When testing, you need to keep the car start state Alternator State: Show the battery/engine status by measuring the voltage(V); Good (LED light on) means the engine voltage is stable and working normally: Faut (LED light on) means the engine voltage is below the normal working range Battery State: Show the change of battery power during charging by LED light; Fu (LED light on) means fully charged; Middle (LED light on) means half power; LOW (LED light on) means less power Check Before Charge: Check whether the engine/battery status is normal before charging OK (LED light is on) means the status is normal. LED light is not on, it means the voltage of the engine/battery is lower than the normal working range, and the battery may have been lifted badly Specifications: Voltage: 12V Product size: 12.4 x 5.1 x 2cm Wire length: 25cm Product weight: 80g Certification: CE