OBD2 Battery Cranking Voltage Test
See how reported voltage changes while the engine is started. OBD CAN records a trace and summary values for review. This is not a battery capacity test or a prediction of remaining life.
What the test measures
The app reads voltage exposed by the OBD adapter and records samples. Results can include static, minimum and recovery readings, duration, sample count and a chart. A status label summarizes the trace; voltage alone cannot establish capacity, cold-cranking amps, battery health, charging-system condition or remaining life. Unsupported adapters cannot provide useful readings.
Prepare and run the test
- Use a compatible BLE OBD2 adapter and connect it to the vehicle. Sign in and open Battery Test; this test requires Premium membership.
- For the suggested cold-battery procedure, leave the engine off for at least an hour. Turn the ignition to ON without starting the engine. For a push-button vehicle, follow the vehicle maker's instructions for accessory or ignition mode.
- Tap Start Test. The app checks engine RPM and asks that the engine be off before sampling.
- When prompted, start the engine once. The app records the voltage change and detects the start event; it may complete automatically. You can stop the run from the screen.
- Review the values and time-series chart. A completed report can be saved in local diagnostic history for later review.
How to use the readings
Review the minimum and the change from resting voltage through starting and recovery. Compare only tests with similar temperature, vehicle state, adapter and procedure. An unusual trace is a reason to use proper battery and charging-system equipment. The label is guidance, not a professional load test or component diagnosis.
Illustrative example: investigate a slow start
Suppose the engine cranks slowly on a cold morning. After the recommended rest, the owner connects the adapter, records a start and reviews static, minimum and recovery values. If the trace looks unusual, arrange a professional battery and charging-system test before relying on the car for a trip. The OBD trace cannot establish battery health, explain slow cranking, rule out a starter or connection issue, or predict remaining life.
Compatibility and limits
Sign-in, Premium membership, an BLE OBD2 adapter that responds to the voltage request and an active vehicle connection are required. Some adapters expose no usable value. This is not a calibrated measurement at the battery terminals. Follow the vehicle's starting procedure and keep clear of moving parts.
Frequently asked questions
Does this estimate battery life?
No. It records voltage around a start, not battery capacity or remaining life.
Why is the reading unavailable?
The adapter may not support the request or the connection may have failed. Check both before retrying.
Should I replace the battery based on one result?
No. Treat the chart as an observation and seek a shop's battery and charging-system test before replacing parts.