I have tested this on both truck and mower batteries and it appears to work very well for charging flats. As others have pointed out, the clips are not of great quality and do not grip very tightly. I have not tested the other functions.
I purchased this item thinking it would be a good thing to have when i dont have another car to get a jump. Man was i wrong. First of all it had a small dent in the bottom, but the package was fine. Maybe i just got a bad one. The engine start feature is worthless. Might get a small grunt from the engine. Nothing close to starting from dead. The 30 amp boost setting does nothing. I tried the charge / maintain option, and after 2 hours it said it was 100% charged ... I still got no more than a grunt from the motor ... I have tried this thing 4 different times hoping for a better outcome, and each time it just wasted my time until i could get a real jump. My last try was when my boys car was dead because he left a light on. The battery was only 2 weeks old and the car had a new alternator. I spent over 8 hours trying every setting on this thing, and still had no luck getting the car started. I jumped the car and let it run 5 minutes, and it was fine. I wouldnt trust this thing to charge a flashlight. I will go back to a cheap charger that works. It is sad how the quality of diehard and craftsman has went to the dumper over the last 20 years.
Works and performs very well.