A battery's reserve capacity indicates what?

A battery's reserve capacity specifically refers to the amount of time it can deliver a specified current, which is usually measured in minutes at a certain discharge rate (commonly 25 amps). This measurement is critical for determining how long a battery can sustain electrical loads without being recharged, particularly in situations where the engine is not running.

For example, if a battery has a reserve capacity of 120 minutes at a 25-amp load, it means that the battery can provide that load for two hours before being depleted. This information is especially important for starting vehicles or powering accessories when the alternator may not be operational or when the vehicle is off.

Understanding reserve capacity helps in selecting the right battery for specific vehicular needs, especially in vehicles with heavy electrical demands or when frequent short trips prevent the battery from being fully recharged.