Battery Maintenance
How to Test a Car Battery (Voltage, CCA & Load)
Multimeter, load tester, BMS reading — what each tells you and what they don't.
6 min read · 15 November 2025
Voltage test (basic)
Engine off, multimeter across the terminals: 12.6V+ is fully charged, 12.4V is 75%, 12.2V is 50%, below 12V is heavily discharged. This only tells you state of charge, not battery health.
CCA load test (better)
A proper load tester applies a high current draw and measures voltage drop. This is the only reliable way to check whether your battery still has the cold cranking amps printed on its label.
BMS diagnostic (best on modern cars)
On AGM/EFB start-stop vehicles, the only way to know what the car thinks of its battery is to read the BMS data via diagnostics. Our mobile technicians do this on every job.