Got to use this more times than I would like while diagnosing a parasitic battery drain on one of my cars. Charges up quickly and simple to use. I was able to start the car in override mode even when the battery had dropped below 4V. I much prefer keeping these in my car emergency kits than jumper cables (big and heavy, need to find a willing good Samaritan) or a lithium battery pack (potential fire hazard and need to remember to keep charged). BTW, my battery drain was from a bad alternator diode.