The EV drives but the 12 V battery slowly goes flat and accessory systems misbehave.
The DC-DC converter is not supplying the 12 V rail from the HV pack.
Suggested test plan
- Measure the 12 V rail in ready mode.
- Verify HV input to the converter.
- Read converter codes.
- Replace or repair the converter.
Safety: High voltage can be lethal. Only trained technicians may work on an EV. Use rated PPE and follow the manufacturer isolation procedure. This is an educational model only.
The DC-DC converter replaces the alternator in an EV. A failing converter produces confusing low-voltage symptoms.