With the engine running, how much voltage should be across the battery terminals?

With the engine running, how much voltage should be across the battery terminals?

• A. 13-15 volts
• B. 12-13 volts
• C. 16-18 volts
• D. 10-12 volts

Answer: (A)

When the engine is running, the alternator charges the battery and the system voltage is kept in a charging range of roughly 13 to 15 volts. This higher voltage compared to the resting battery value (about 12.6 V) ensures the battery can accept a charge and the electrical system has enough power under load. So reading across the terminals in the 13–15 V range is normal. Seeing 12–13 V would be more typical of a resting battery, while 16–18 V would suggest overcharging and 10–12 V would indicate the system isn’t charging properly or the battery is very discharged.

When the engine is running, the alternator charges the battery and the system voltage is kept in a charging range of roughly 13 to 15 volts. This higher voltage compared to the resting battery value (about 12.6 V) ensures the battery can accept a charge and the electrical system has enough power under load. So reading across the terminals in the 13–15 V range is normal. Seeing 12–13 V would be more typical of a resting battery, while 16–18 V would suggest overcharging and 10–12 V would indicate the system isn’t charging properly or the battery is very discharged.