Firmware mismatches and BMS resets usually require remote or on-site engineer access. A diagnostic session identifies the exact cause and the correct fix route.
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CAN (Controller Area Network) is the communication protocol that most solar battery systems use to allow the inverter and battery to talk to each other. Over this link the inverter sends charge and discharge commands; the battery returns state of charge, voltage, temperature, and cell health data.
When this communication path breaks down, the inverter cannot safely control the battery. As a protection measure, it disables battery operation entirely and raises a communication fault alarm.
The break can be in the physical cable, the communication ports on either device, the protocol version (caused by firmware mismatches), or a locked BMS that isn't responding to communication attempts.
Do not open your battery or inverter enclosures. Battery packs contain high-voltage DC — typically 48V to 400V depending on system type. This voltage is present even when the AC supply is isolated. There are no user-serviceable components inside. All physical inspection of internal components must be carried out by a qualified engineer.
Listed from most to least commonly encountered.
Inverter and battery firmware updated to incompatible versions — typically after a cloud-pushed update that updates one side but not the other. The CAN protocol versions no longer align.
The BMS cable between inverter and battery is not fully seated, has been pulled under tension, or the RJ45 clip has broken. Causes intermittent or persistent communication loss.
The battery BMS has entered a protection state — from over-discharge, cell imbalance, over-temperature, or a hard fault — and is not responding to communication attempts.
Many inverters require the BMS communication protocol to be manually set to match the battery brand (e.g. Pylon, BYD, GivEnergy, custom). An incorrect protocol setting means the two devices transmit on different 'dialects' and cannot understand each other.
Less common. The CAN communication port on the inverter or battery has failed — from power surge, physical damage, or hardware defect. Requires component replacement.
In multi-battery systems, the CAN bus requires correct termination resistors at each end of the daisy chain. Missing or incorrect termination causes communication instability across all batteries in the stack.
These are the checks you can make without opening any enclosures.
Open the event log in your monitoring portal and record the exact fault code and the time it first appeared. Different codes indicate different parts of the communication path. For GivEnergy faults, see the GivEnergy fault codes guide. The code and timing are the most useful information you can bring to a diagnostic session.
Look at the event log timeline. Did the fault appear immediately after a firmware update notification? After a power cut? After a particularly cold or hot period? The timing often points directly at the cause — firmware mismatch, protection trip, or environmental trigger.
Without opening any enclosures, look at the communication cable between the inverter and battery — typically an RJ45 cable going into a BMS or CAN port on the side or bottom of each unit. Check it is firmly plugged in at both ends and hasn't been disturbed. A partially seated connector can cause persistent faults.
Turn off the inverter via its AC and DC isolation switches. Turn off the battery using its own shutdown button or circuit breaker. Wait 2 full minutes. Turn the battery on first, wait 30 seconds, then turn the inverter back on. Allow 5 minutes for the communication to re-establish. Check whether the fault has cleared in the portal.
Look at the battery unit itself for status LED indicators. A red or amber light on the battery (separate from the inverter) suggests the battery BMS has its own fault or is in a protection state. Note what colour and pattern of lights you see — this informs whether the battery needs a BMS reset rather than a communication cable fix.
Communication faults are one of the more complex fault types — the exact cause determines whether it is a cable fix, a firmware update, or a hardware replacement. A remote diagnostic session reviews your event log, firmware versions, and fault history to give you a clear answer.
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