The short answer
Check the battery switches are on and the battery connection.
Plain explanation
From the Growatt manual for the SPH 3000-6000TL BL-UP: Check battery switches are ON. Installer checks battery connection. 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
- Check battery switches are ON
- Installer checks battery connection
Source
Growatt SPH 3000-6000TL BL-UP Installation & Operation Manual (Growatt doc, distributor-hosted), §9.2 Fault list, §9.2 Battery Openmidsummerwholesale.co.uk ↗
Where installers ask this
- Help, Growatt + Pylontech (r/SolarDIY)
- reddit.com/r/SolarDIY/comments/1rovstx/
- reddit.com/r/SolarUK/comments/1c4gv9q/
- reddit.com/r/SolarDIY/comments/1mbxinp/
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.