Which battery rating is expressed in minutes?

The rating that is expressed in minutes is the reserve capacity. This rating measures how long a fully charged battery can continuously supply a specified load (typically 25 amperes) before its voltage drops to a level that is no longer usable, usually considered to be 10.5 volts. Reserve capacity is crucial in automotive applications because it indicates how long a vehicle can run its electrical accessories in the event of an alternator failure or other issues that may prevent the battery from receiving a charge.

In contrast, cold-cranking amperes (CCA) and cranking amperes (CA) measure the battery’s ability to deliver a high burst of energy necessary to start an engine in cold temperatures or under load, specified in amperes, rather than minutes. Battery voltage test evaluates the health of the battery by measuring its voltage at rest, but again, does not provide a time-based measurement. Therefore, reserve capacity is the only rating specifically associated with a time duration in minutes, making it the correct answer.