Review on 12/24V DC Automotive Battery Tester with Large Clamps and LED Display - Ultimate Diagnostic Tool for Alternator/Battery Check in Cars, Motorcycles, and Trucks by Darryl Blumenthal

This tester works well. I always have it in my car to check the battery before a trip. Without warning, my car completely lost power while driving. After the mechanics couldn't figure out what was wrong, I replaced the alternator myself and use it to make sure the alternator is charging the battery properly. My only complaint is that the instructions weren't very clear. Usually the green alternator status light stays on, but sometimes it goes out and the red alternator fault light never comes on. I don't know what this script is pointing to. Does the alternator then charge the battery properly or not? Also, it's a great tester to carry around in your car.