BYD DOLPHIN charges on DC but not AC: should the onboard charger be replaced first?

If a DOLPHIN charges on DC equipment but will not charge on AC equipment, do not rush to buy an onboard charger. The difference warrants inspection, but external power, charging equipment and vehicle-side AC conversion must be distinguished before deciding on replacement.

AC and DC charging provide different clues

The onboard charger is commonly abbreviated OBC. Before AC power can charge the traction battery, it must be converted to DC in the vehicle. Würth Elektronik's technical explanation distinguishes the two charging methods and onboard conversion.[OBC function explanation][S2]

Successful DC charging therefore confirms only some charging conditions, without independently proving normal onboard AC conversion. Equally, AC charging failure does not directly prove OBC damage. The symptom helps narrow the inspection path; it does not justify skipping other checks.

Start with the external conditions in the troubleshooting table

The DOLPHIN handbook's charging fault table lists equipment faults, interrupted AC supply, abnormal connections and battery temperature.[DOLPHIN handbook page 71][S1] Compare vehicle messages with charging equipment status, rather than diagnosing an assembly from “it did not charge when plugged in”.

Record the charging method, when charging stopped and the messages from both vehicle and equipment. If equipment or the port has obvious damage, looseness or corrosion, stop using it and arrange attention. Do not keep connecting suspect equipment simply to try again.[Handbook pages 68, 71–72][S1]

OBC replacement requires vehicle-side inspection results

After external conditions have been checked, the repairer still needs to inspect the AC charging path and related controls using the vehicle's service information. Any recommendation to replace the OBC should identify the checks supporting an internal fault and the other possibilities excluded.

A single recovery after clearing a message or reconnecting does not establish the cause. Conversely, one unsuccessful charge does not justify replacement. For intermittent problems, retaining the conditions and actual messages helps reproduction more than specifying a new assembly in advance.

A function name may not be a separately supplied part name

Bosch's public product material shows a design integrating OBC and DC-DC functions.[Integrated charging conversion design][S3] This illustrates why the “onboard charger” function and the assembly available for service purchase need separate verification.

If a quotation groups several names together, confirm the component and permitted repair scope against the actual vehicle documentation. Separate OBC replacement on another model does not establish that DOLPHIN allows it. Equally, an integrated design elsewhere does not establish that this vehicle requires complete assembly replacement.

Verification reminder

Verify compatibility or interchangeability using the VIN and local manufacturer parts catalogue. No public data was available for vehicle-specific OBC test thresholds, fault-code meanings, integrated or separate supply boundaries, OE numbers or candidate-part certification. [To be verified] Supplier designs provide functional background only and do not prove that their products are installed on this vehicle. Inspect and repair the vehicle-side charging system using professional service procedures.

For DOLPHIN charging-system parts, use the parts enquiry page.

[S1]: https://bydautomotive.com.au/brochures/BYD-DOLPHIN-Owners-Handbook-2023.pdf
[S2]: https://www.we-online.com/en/components/applicationguide/on-board_charger
[S3]: https://www.bosch-mobility.com/en/solutions/power-electronics/charger-converter/