The leading cause of battery misdiagnosis is… re-testing a vehicle's battery without acknowledging the first result.

We recommend vehicles are battery tested upon arrival into a workshop, but if test results are not acknowledged the first time, it can alter the overall diagnosis of a vehicle.

Battery misdiagnosis costs workshops time, money, and reputation, as vehicles are continue to break down after leaving the workshop. Testing a battery multiple times often provides different results, confusing technicians and preventing correct battery management solutions.

Factors that impact upon battery test results in a short space of time include:

- Location: Testing a battery outside a vehicle produces varied connection interference, such as extra resistance along the cable length.

- Rest time: If a battery doesn’t rest for 15 minutes before a test, previous charging/discharging will impact results due to added surface charge.

- Data input: Different battery tester inputs, such as battery type, rating, and AH (amp hour), will output different results. The tester must recognise the correct battery type to output accurate results.

- Age: The age and type of battery can change results quickly. Each technology performs differently at a different voltage level and has a varied resistance. Different standards are also used in each technology, such as ENSAE and DIN, to measure performance (cranking amp measurements).

- Temperature: If the temperature sensor is pointing in different directions, results will change due to different temperature readings.

The first test when a vehicle enters a workshop should always be treated as the most accurate - it's the most likely to have limited influencing factors.

To make sure the first test is accurate, always double-check a battery tester's inputted data to avoid undetected battery misdiagnosis. If a battery tester is operating noticeably inaccurate during the test, we recommend a service and calibration is performed.

Battery maintenance technology is constantly improving with each new product release, so we recommend older products are replaced to make sure test results are calculated using the latest technology available.

Best Practice Checklist for Battery Testing

- Rest the battery for 15 minutes before testing, to remove any surface charge.

- If this isn’t possible, the Midtronics CPX900 can correctly diagnose a battery by identifying and discounting potential surface charges.

- Perform one battery test. Multiple tests are proved to provide no benefit and can result in reduced test result accuracy.

- Check, check and check again to make sure battery test data is inputted correctly.

If you have any further questions on how to reduce battery misdiagnosis, please contact us on 0121 514 0605.