This wonderful battery diagnostic tool tests everything about your battery, including its starting and charging system. In fact, we were able to point out a warranty repair to the dealer that the alternator wasn't charging the battery correctly. (He just wanted to replace the battery which wasn't under warranty...) We received a new battery (at no charge, due to the faulty alternator) plus they solved the alternator problem! It paid for itself with one use! Cables measure 18" long, and it works on all 12 volt Conventional, Maintenance Free, AGM, Gel Cell, Marine and Deep Cycle batteries. Easy-to-use, and easy to read with LED display. If you have multiple cars, this tool is invaluable.