The short answer
The first digit shows the module position; check its connections and use the module exclusion method.
Plain explanation
From the BYD manual for the Battery-Box Premium HVS/HVM: Read the code: first digit shows the module position. Installer checks that module's connections. The rest of the checklist is below; work through it in order. Installer only: DC and AC work on a live PV system is dangerous, so owners should note the code and call their installer.
Steps from the source
- Read the code: first digit shows the module position
- Installer checks that module's connections
- Use the module exclusion method to find the faulty module
- Service if confirmed
Source
BYD Battery-Box Premium HVS/HVM Service Guideline & Checklist (BCU2.0) V1.1, 2025-08-08, §2.9 + §2.11 p14www.bydbatterybox.com ↗
Where installers ask this
- BYD HVM expansions - combiner box (r/solar)
- reddit.com/r/DeutschePhotovoltaik/comments/1wq5in6/
- reddit.com/r/DeutschePhotovoltaik/comments/1mxjxdd/
General guidance based on the manufacturer's manual or the named source. Always follow the current manual for your exact model and your national code. DC and AC electrical work is for qualified installers only. Not affiliated with or endorsed by any brand named; trademarks belong to their owners.