In addition to how we test car batteries for endurance, our reserve-capacity test measures how long an auto battery can supply power if the charging system fails or if you leave your headlights or accessories on. The lowest-scoring models in our test should provide 1½ hours of power. Higher-scoring models can supply power well past 2 hours.
We also test for cold-cranking amps (CCA). That’s the measure of current that’s available at 0º F and is the primary indicator of cold-climate performance. CCA has long been a major selling point for batteries. But we believe that the industry’s claimed CCA doesn’t reflect real-world conditions because batteries are charged at a higher voltage than the 14.5 volts provided by most vehicles’ alternators. Our CCA test is based on more realistic charging voltages and amperage demands, and our results show each battery’s relative cranking power, regardless of the manufacturer’s claims.
