The short answer
Here is BYD's own checklist from its service guideline.
Plain English
BYD Battery-Box HVS / HVM not charging or discharging? Here is BYD's own checklist from its service guideline.
Why it happens
Once the battery and inverter communicate, the BCU closes the relay. Only then is there output voltage.
The fix, step by step
- Installer Check the configuration against BYD's latest Compatible Inverter List (V2.19 or above) and make sure the inverter is configured correctly
- Installer Check the app configuration was completed and the firmware is the most recent one
- Installer Terminal resistor: one tower, plug it into the IN port. Parallel towers: OUT port of the master and IN port of the last slave
- Installer Inverter not showing battery SOC and temperature? Confirm the PIN / cable configuration for your inverter model, replace the comm cable (min. CAT5, better CAT7). Fronius and SMA: check the enable signal
- Installer Connect the Battery-Box directly to the house ground bus, not over the inverter casing or other devices
- Installer Relay closed? Check for output voltage in Be Connect 2.0 / Be Connect Plus, or whether the inverter shows the battery voltage
- Installer Defined restart: battery off (LED button 5 s), inverter DC off, AC off, wait 1 minute, battery on, AC on, DC on (Kostal only: pull the PV strings before waiting and reconnect them after battery on)
Safety. BYD: all work and measurements on the Battery-Box are only allowed by professional, qualified electricians. High voltage.
Source
BYD Battery-Box Premium HVS & HVM Service Guideline and Checklist for BCU-V2.0, V1.1, Section 2.4 Battery <> inverter communication / no charging or discharging, page 6.www.bydbatterybox.com ↗
Where installers ask this
- Fronius Gen24 + BYD: battery no longer charging? (r/fronius)
- reddit.com/r/DeutschePhotovoltaik/comments/1vjn81v/
- reddit.com/r/fronius/comments/1i11q4t/
- reddit.com/r/DeutschePhotovoltaik/comments/1pfn6m1/
- reddit.com/r/DeutschePhotovoltaik/comments/1ckxc0b/
The full answer
Different inverter or a different symptom? Ask us.
Ask a question →General guidance based on the manufacturer's manual. Always follow the current manual for your exact model. Steps marked INSTALLER ONLY must be done by a qualified electrician. Not affiliated with or endorsed by BYD; trademarks belong to their owners.