A cheap multimeter is one of the best tools you can own. Here’s how to use it on a battery.

Quick answer With the engine off and everything shut off, a healthy, fully charged battery reads about 12.6 volts. Around 12.4 is roughly 75% charged, about 12.2 is half, and 12.0 or below is nearly flat. While cranking, it shouldn’t drop below about 9.6 volts. A parts store can also do a free load test.
How to Test a Car Battery with a Multimeter
Photo: Jacek Halicki / Wikimedia Commons, CC BY-SA 4.0
Tools & materials

  • Digital multimeter
  • Gloves and eye protection
  • Wire brush (if terminals are corroded)

Steps

  1. Let the car sit at least an hour with everything off. Overnight gives the truest reading.
  2. Set the meter to DC volts, 20V range.
  3. Red probe on the + terminal, black on the −. Read the voltage.
  4. Read it: 12.6–12.8 V full; ~12.4 V about 75%; ~12.2 V about 50%; ~12.0 V about 25%; under ~11.8 V discharged.
  5. Cranking test: have a helper crank the engine while you watch the meter. If it dips below about 9.6 V, the battery is weak even if the resting number looked fine.
  6. Charging check: with the engine running, the reading should rise noticeably above the resting number. If it doesn’t, the alternator or wiring may be the problem rather than the battery.
  7. If it reads low, charge it fully and re-test the next day. A battery that won’t hold a charge needs replacing.
Safety: Keep tools from bridging the two terminals. Wear eye protection, and don’t smoke or make sparks near a battery.

From https://www.djgaston.com/test-a-car-battery/ · Updated October 22, 2026