Inverex Nitrox F58 — BMS Communication Fault

What it means: The inverter has lost its data link to the lithium battery's BMS. Inverex's hybrid fault table describes F58 as telling you that "the communication between hybrid inverter and battery BMS disconnected", raised while the inverter's "BMS Err Stop" protection is active. Without that link the inverter cannot read the pack's real cell voltages, temperature or state of charge, so it has no reliable way to know when to stop charging or stop discharging — which is why it stops instead. This meaning is specific to the Nitrox hybrids. On the three-phase Nitrox string inverters, which have no battery at all, F58 is a completely different fault ("AC grid U over current"), so do not read a hybrid answer off a string-inverter table or vice versa.

Why does Inverex show F58?

• Loose, damaged, pinched or wrongly wired BMS communication cable between pack and inverter
• Wrong battery brand or protocol selected in the inverter's battery menu
• Cable in the wrong port — the Nitrox exposes both RS485 and CAN and lithium packs differ in which they use
• Battery pack powered down, or its own breaker or isolator switched off
• The pack's BMS sitting in a protection state of its own
• An incompatible battery paired to the inverter during a DIY or cut-price upgrade

The Pakistan factor

F58 shows up here most often after an upgrade from a tubular lead-acid bank to lithium in which the pack was fitted but the comms cable and battery protocol were never set up. The inverter then runs a lithium bank on a lead-acid voltage profile with no BMS link at all, which is one of the standard ways packs get overcharged in Pakistani installs. The shortcut of simply disabling "BMS Err Stop" circulates widely in local installer and dealer WhatsApp groups because it clears the alarm in seconds, and it is the single most dangerous piece of advice attached to this code — it converts a protective stop into silent, unmonitored charging. Heat compounds it. A lithium pack sitting in a hot, unventilated store room depends on its temperature-based protections, and a lost comms link is exactly what takes those away from the inverter.

How to fix it

1. Read the display and note whether "BMS Err Stop" is showing. That is the protection the manual ties to this code — the inverter has deliberately stopped rather than charge and discharge a battery it cannot see.
2. Check only what is visible from outside, without opening anything. Is the battery's own breaker or isolator on, is the pack powered up, is the comms cable seated at both ends and not crushed, pinched or chewed.
3. Have your installer confirm that the battery brand and protocol set in the inverter menu match the pack you actually own, and that the cable is in the correct RS485 or CAN port. This is only a settings check, but getting it wrong on a lithium bank has real consequences, so have it done by whoever commissioned the system if you are not certain.
4. Do not open the battery, and do not try to "reset the BMS" by disconnecting cells, terminals or the pack's internals. A BMS that has latched a protection is reporting something real about the pack, and a reset only hides it.
5. Do NOT disable "BMS Err Stop" to clear the message. The manual does list this as an option, but switching it off does not restore communication — it only removes the inverter's instruction to stop when it cannot see the battery, leaving the pack to be charged and discharged blind. That setting belongs to your installer, and only with a stated reason.
6. If the cable and settings check out, or you cannot verify them yourself, stop and call your installer or an Inverex service centre. The manual's own escalation for a persisting F58 is to contact them.