Log #8 - Battery Diagnosis and Charging-System Check

Battery Replacement and Electrical Safety Note

July 5, 2026

Removing the battery hold-down bracket.
Old battery label details.
Resting battery-voltage measurement.
Alternator charging-voltage test.
Voltage after external charging.
Battery tray and main wiring.
Installing the new Varta D24 battery.

Initial Battery Diagnosis

The vehicle had an older Halk 12 V, 60 Ah, 520 A battery manufactured in February 2022. After the car had been parked for approximately four hours, its resting voltage measured 12.18 V. With the engine running, the charging voltage measured 13.97 V.

Replacement and Follow-up Measurement

The old battery was taken to a battery shop and fully charged. After a further 24 hours of rest, its voltage had fallen to 12.12 V. It was traded in for a Varta D24 12 V, 60 Ah battery manufactured in 2024. After installation and approximately four hours of rest, the new battery measured 12.89 V.

Important Safety Correction — 13 October 2026

An earlier note said that the negative battery terminal had been disconnected while the engine was running. This is not a safe alternator test on a modern vehicle. Disconnecting the battery while running can cause voltage spikes and damage the alternator diodes and electronic control units. Do not repeat this procedure. Check charging performance with a multimeter using the correct measurement method.

Conclusion

The replacement battery showed a substantially higher resting voltage after installation. Charging-system checks should be performed with suitable instruments, without disconnecting the battery while the engine is running.