Battery Drain
Workflow for repeated dead battery after sitting, separating weak battery, charging issue, and parasitic draw.
A battery drain complaint is not automatically a bad battery. The useful split is whether the battery fails capacity testing, the alternator does not recharge it, or a draw remains after shutdown.
Common Sounds or Signs
- Battery dead after sitting overnight or several days
- Jump start works, then problem returns
- Interior light, module, or accessory stays awake
- Slow crank with no obvious charging warning
Quick Checks
- Charge and load test the battery first
- Verify alternator output after the engine starts
- Inspect terminals, grounds, and aftermarket accessories
- Measure key-off draw after modules time out
Inspection Priority
- Verify battery voltage and load-test results first.
- Inspect cable voltage drop and grounds before replacement.
- Confirm starter command or charging output before pricing parts.
Diagnostic Path
Pick the first inspection path.
Battery and Charging Path
Confirm battery capacity and charging output before spending time on draw isolation.
- Load test battery after full charge
- Check charging voltage with loads on
- Voltage-drop terminals and grounds
Parasitic Draw Path
If battery and charging pass, isolate excessive key-off draw without waking modules repeatedly.
- Let modules sleep before draw measurement
- Check glove box, trunk, vanity, and aftermarket loads
- Pull fuse paths only after baseline draw is confirmed
Common Next Steps
Quick checks before expanding the estimate.
Test charging voltage
Measure alternator output and battery voltage under load.
Inspect serpentine belt
Check belt condition, tensioner travel, and pulley alignment.
Verify battery condition
Charge and load test before blaming the alternator or starter.
Related Inspection
Recommended Next Repair Paths
Compare repair paths before replacing parts.
Battery Replacement
Use after capacity testing confirms the battery will not hold charge.
Alternator Replacement
Use when low charging output is confirmed with a known-good battery.