The DieHard 51R is part of the Car battery test program at Consumer Reports. In our lab tests, Car battery models like the 51R are rated on multiple criteria, such as those listed below.

Life: Life test measures how a battery endures repeated charge-and-discharge cycles at hot-climate engine-compartment temperatures. The more cycles endured while maintaining a higher voltage, the higher the score.

Reserve capacity: Reserve capacity estimates how long batteries can run a car if the charging system fails.

CCA: CCA performance reflects voltage at our load of half the average claimed CCA for each group size after cranking for 15 seconds at 0º F. We charged batteries at the 14.5 volts that vehicles typically supply, rather than the higher voltage that manufacturers use. Batteries charged at the lower voltage met BCI voltage standards for a fully charged battery.