Bms Int Fault on a Fox ESS H1 G2 single-phase hybrid inverter: DIP switch at the wrong position; the communication between battery packs is interrupted
Short answer
On a Fox ESS battery, Bms Int Fault means: DIP switch at the wrong position; the communication between battery packs is interrupted. The battery keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 24 September 2026 · 1 source
What it means
The manual says: DIP switch at the wrong position; the communication between battery packs is interrupted.
Part involved: battery pack-to-pack link.
When it shows: Internal battery comms failure.
Likely causes:
- DIP switch wrong; inter-pack comms cable loose.
Is it safe?
| Does the battery stop? | Partly |
|---|---|
| Engineer needed? | Yes |
The battery keeps running with some functions stopped.
Resetting itself: unknown.
Manual reset: Move DIP switch / reconnect cable (installer).
What you can check
- Read the full code and message on the inverter screen or in the FoxCloud app and note the date/time for your installer.
- Check the inverter's AC isolator next to the inverter and the solar/battery breaker in the consumer unit are ON (do not reset a breaker that trips again - call your installer).
What the engineer will check
- Set DIP switches correctly; check inter-pack comms cables.
Who to ask for: Battery/hybrid installer trained on the specific battery (manufacturer-approved installer).
Certification: Battery and hybrid-inverter DC work: installer trained/approved by the manufacturer; electrical work under BS 7671 by a competent person.
What you might notice
Sources
- H1(G2)/AC1(G2) Series User Manual ↗ · V1.0.8 · page 50 · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026