How long will a 12 volt battery run 4 amps?

To determine how long a 12-volt battery will run at 4 amps, you need to know the battery's capacity in amp-hours (Ah). For example, if the battery has a capacity of 50 Ah, you can calculate the runtime by dividing the capacity by the current: 50 Ah / 4 A = 12.5 hours. Therefore, the battery would last approximately 12.5 hours under a constant load of 4 amps. Keep in mind that actual runtime may vary due to factors like battery age and discharge rate.