Update: It’s18 months old and worked on a battery that was completely dead. I had to use the override button but it worked great. Original review: Amazon is selling old stock or their improper storage has damaged the battery upon arrival. These are suppose to charge to 12.8 volts per the label on the back. First one charges to 12.5 volts. Second one to 12.3 volts. This equals about a year of use in my mind. Since I'm paying full price I want a fully charged jumper and not something that is the equivalent of a used 1 year old device.