Home › Fox ESS › BMS Lost
Check & restart

Fox ESS BMS Lost

Updated June 2026 · Reviewed for technical accuracy · ~2 min read

BMS Lost (often shown as Error 14) means your Fox ESS has lost the RS485 or CAN communication link with the battery BMS. The inverter can no longer read the battery, so it stops charging and discharging and waits. This is usually a comms cable problem, a wrong port or a DIP switch setting, not a damaged inverter, and it often clears once the link is restored and the system is power-cycled.

What usually causes it

  • A loose or wrong-port comms cable. The H1 G2 has several similar RJ45 sockets, so the BMS cable is easy to seat poorly or plug into the wrong one.
  • An incorrect DIP switch setting on the battery master unit, so the inverter and battery do not match.
  • A fully discharged battery. If the pack has gone flat, its BMS may be asleep and unable to answer.
  • A damaged or pinched cable, less common, that an installer needs to check or replace.

How to handle it safely

  1. Check the comms cable at both ends. Make sure the RS485/CAN cable is firmly seated at the inverter and at the battery, and in the correct port. On the H1 G2 the sockets look alike, so confirm it is in the BMS port, not a meter or parallel socket.
  2. Verify the battery DIP switch. Check the DIP switch on the battery master unit matches the setting in the manual for your battery count.
  3. Do a full power cycle. Turn the AC isolator off, turn the battery DC off, then wait at least 2 minutes for the capacitors to discharge. Turn the battery on first, then turn the AC back on.
  4. If it persists after reseating cables, do not keep opening connectors. Contact your installer or battery supplier to check the cable, DIP setting and battery state of charge.

Quick decision flowchart

BMS Lost (Error 14) appears
↓ reseat the comms cable and check the DIP switch
✅ Cable was loose or in the wrong port → reseat it, power-cycle, the link returns.
❌ Cable and DIP are correct but it stays → the battery may be flat or the cable faulty, call your installer.
↓
If the comms link is correct and the fault remains, contact your installer or battery supplier.
⚠️ When to call a professional. Reseating a plug-in comms cable and power-cycling are safe owner steps. Do not open the battery enclosure, touch the DC battery cables or probe inside the inverter. A battery that stays unresponsive, a damaged cable or repeated BMS Lost faults need a qualified installer or your battery supplier.

Related Fox ESS codes

Meter Lost Fault Bat Volt Low Internal Comms Fault

FAQ

BMS Lost cleared after a restart, do I still need to worry?

If a full power cycle cleared it and it has not come back, you are most likely fine. It often means a cable was slightly loose and reseating plus the restart fixed it. If BMS Lost keeps returning, the cable, the port or the DIP switch is still off and your installer should check it.

Why do I have to wait 2 minutes before turning it back on?

The inverter holds charge in its capacitors for a short while after the power is off. Waiting at least 2 minutes lets them discharge so the system makes a clean fresh start when you power the battery on first, then the AC. Powering up too quickly can leave the comms link in the same stuck state.

Helpful guides

Error codes explained How to safely restart your inverter

Sources

  • Fox ESS H1 G2 inverter user manual and FoxCloud alarm list (BMS Lost / Error 14 = lost RS485/CAN communication with the battery; check comms cable, port and DIP switch).
  • Fox ESS battery installation guidance on the BMS comms port, DIP switch setting and the correct power-up sequence.
⚠️ Safety disclaimer. Solar inverters and batteries carry lethal DC and AC voltage even when "off". This guide covers reseating a plug-in comms cable, checking a DIP switch and a power cycle only. Any battery DC wiring or internal work must be done by a licensed installer or electrician.