My car's battery always has problems with discharge, I always have to jump start it if I don't drive it for a week or two. This charger kept my battery well charged, I took a quick reading after a week of use. Jet charge, read 12.8 volts, which is a good number. I have never had to use the full charge function (from a dead battery) and hope I never have to. Just trickle charge mode and it seems to be doing the job just fine. I will continue the strength tests when the car is in winter storage!