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Fault guide · GivEnergy battery

GivEnergy BMS Comm Fail: Diagnostic Guide

Your GivEnergy inverter has lost communication with the battery's BMS (battery management system). The app or portal shows STORAGE_WARN_BMS_COM_FAIL or STORAGE_ERROR_BMS_COM_FAIL, or the battery shows as disconnected. It happens on LV systems, where the battery talks to the inverter over RS485, and on HV systems, where the link is CAN. This guide covers the causes in order of likelihood.
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  • Covers LV (RS485) and HV (CAN) battery systems
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BMS Comm Fail is hard to pin down without the event log

The exact sequence of events in your inverter's log (which events appeared, in what order, and when) tells us whether this is a cable fault, a firmware issue or a BMS protection event. We can review this remotely.

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Ronald at Solar Tech Support was very quick and knowledgeable in helping me restart my GivEnergy solar electric battery. I would highly recommend his services.

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I contacted Solar Tech Support because I had a problem with my legacy GiveEnergy installation. within 24 hours they had diagnosed the problem and offered advice on resolution. Because they were unable to fix the problem there was no charge! This despite numerous time consuming emails. I am currently trying to engage with the original installer but if that is unsuccessful I will go back to Solar Tech Support and ask them to repair the system with a retrofit. Very knowledgeable and responsive. I highly recommend them.

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After recently changing my fuse board the ct clamp broke, this meant my inverter was not communicating properly with my GivEnergy system. After several people letting me down, finally got put in touch with Ron. He came out within 24hours & resolved the fault within an hour, no fuse just got on with it. Work was tidy & arrived when he said he would. Ron followed up a few days later to confirm all was still good, great service from all involved.

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Written by · Independent Solar Engineer Last updated

WHAT THE LINK DOES

How the battery talks to the inverter

The battery's BMS (battery management system) sends the inverter its state of charge, temperatures and protection signals, and the inverter sends back charge and discharge commands. LV GivBat packs (51.2 V) do this over RS485: through the plug-in battery cable on Gen 2 and Gen 3 batteries, or a separate data cable on Gen 1. HV battery kits do it over CAN. Without this link the inverter cannot safely run the battery.

WHAT BREAKS

The data link, not the battery

BMS Comm Fail doesn't necessarily mean the battery is damaged. It means the communication between the battery and the inverter has been interrupted. The cells themselves are usually fine; the system can't talk to them. This matters for whether the fix is remote or on site.

WHAT YOU SEE

The event in the app or portal

The event log shows STORAGE_WARN_BMS_COM_FAIL (warning) or STORAGE_ERROR_BMS_COM_FAIL (error). In the app: your device → Event History. In the portal: My Inverter → Event Log. The battery may show as disconnected, with state of charge at zero or N/A. On the battery itself, an amber or yellow status light usually means the BMS is not talking to the inverter.

Do not open the battery or inverter enclosure. The comms cable connects at the outside of the battery and the underside of the inverter, and looking at those plugs is safe. Do not remove any covers or touch internal parts. If you're unsure what you're looking at, contact a qualified engineer.
Start here
Quick checks

Before anything else, check these

Two checks that take under a minute and rule out the most common causes.

1
Check the battery is switched on

The GivEnergy battery has a power button on the side panel. If it has been turned off by accident, after a power cut, during a house move or by someone in the household, the battery will appear as disconnected and the inverter will log a BMS Comm Fail event. Press and hold the button until you hear a beep and the LED indicators light up.

Also check that the DC MCB isolator is in the UP / ON position. Gen 2 and Gen 3 batteries have it built in, behind a cover on the battery; on Gen 1 batteries it is a separate breaker between the inverter and the battery. If it is down, no DC power flows between the battery and inverter, although the comms stay connected.
2
Check the battery comms cable at both ends

The communication cable runs between the underside of the inverter and the battery. What it plugs into depends on the generation:

  • Gen 1 inverter and Gen 1 battery: a green pin connector on a separate data cable. Gen 1 battery power is on cable lugs.
  • Gen 2 inverter: an RJ45 BMS port.
  • Gen 2 and Gen 3 batteries, Gen 3 inverter: a plug. On the batteries the same plug-in cable also carries battery power.
  • HV kits: the link is CAN, on the orange HV-kit connector.

Look at the connector at each end: it should be fully home, with its clip engaged where it has one. A connector that isn't fully seated is a common cause of on-off comms faults, particularly on newer installations where it may not have been pushed fully home at commissioning. If one looks loose, don't pull or push it with the system running. Tell us, and an engineer will reseat it with the system isolated.

Cause 1: try first
Power cycle

Restart the inverter and battery

Many BMS comms faults, particularly those triggered by power interruptions, brief grid outages or software glitches, clear after a controlled restart. This should always be the first active step after the quick checks above. One exception: if the battery or inverter is flashing red and green together, a firmware update is in progress. Leave it alone and do not switch anything off.

1
Start with a battery-only restart

It clears many BMS communication faults without powering the whole system down, and no isolator moves. Follow the battery-only restart steps for a Hybrid or an AIO.

2
Fault back within 5 minutes? One full restart, in the correct order

The battery goes off first and the DC MCB last, then the AC comes back on first. Shutting the inverter down while the battery is still live can latch a BMS protection state, so the order matters. Follow the full sequence for a Hybrid or an AIO.

After restart: Allow 5–10 minutes for the inverter and battery to re-establish communication. Check the event log for whether the BMS Comm Fail event has cleared. If the fault comes back within minutes of restarting, there is a persistent cause underneath. Carry on through this guide.
Cause 2
Physical: needs a site visit

Comms cable or set-up fault: loose, damaged or wired wrong

If the restart doesn't clear the fault, the communication cable between the inverter and battery is the next suspect. On LV GivBat systems the link is RS485, in the plug-in battery cable on Gen 2 and Gen 3 batteries or a separate data cable on Gen 1. At the inverter it lands on a green pin connector on a Gen 1, an RJ45 BMS port on a Gen 2 and a plug on a Gen 3; a Gen 1 battery also uses a green pin connector. On HV kits it is CAN. Either way it is a physical connection, and physical faults need a site visit to put right. A remote diagnostic can confirm the cable is the likely cause first.

Common cable and set-up faults

→Plug not fully seated: the cable looks connected but isn't clicked fully home. Most common on new installations.
→Gen 2 inverters: the thick comms cable crimped straight into the RJ45 plug. The commonest Gen 2 fault we see, explained below.
→Wrong port, or wired wrong at one end. Shows as BMS Comm Fail from the very first start-up.
→Damaged cable: crushed, bent sharply or chewed by rodents. Can cause on-off faults that are hard to pin down.
→LV stacks: two packs on the same dip-switch address. Every battery needs its own address, so a new or moved pack left on the wrong setting drops out.
→HV kits only: the CAN chain needs its terminator in place. LV packs have no terminator, so this never applies to them.

Signs pointing to a cable or set-up fault

→Fault appeared straight after installation (wiring, addressing or, on HV kits, termination)
→Fault comes and goes: clears after a restart, then returns within hours or days
→Fault appeared after work near the inverter or battery (cable disturbed)
→More than one battery, and only one or some drop out
→A restart clears the fault for a while, but it always returns
Gen 2 inverters

The commonest Gen 2 fault we see: the comms cable crimped into the RJ45 plug

On a Gen 2 inverter the battery comms go into an RJ45 BMS port. The BMS comms cable is too thick for an RJ45 plug, so crimping it straight in causes comms faults.

It is common practice in the field to join it to a thinner Cat5 cable with Wago-type connectors and crimp the Cat5 instead, to stop the problem. This is an engineer job: do not unplug or re-crimp anything yourself.

What you can safely check yourself: Look at the comms connector on the battery and on the underside of the inverter. Confirm each one is fully seated, with its locking clip engaged where it has one. Do not open any covers and do not unplug anything. If the cable looks connected but the fault persists, the problem is likely inside the plug or the cable itself, or in the battery addressing. A qualified engineer needs to test the cable and check the set-up.
Cause 3: common after updates
Common after updates

Firmware mismatch between inverter and battery

The GivEnergy inverter and battery run separate firmware, and the two must be compatible. If one is updated and the other isn't, they can stop understanding each other and communication breaks. GivEnergy's Gen 3 battery manuals also say every battery in a stack must be on compatible firmware.

How to check firmware versions

Inverter firmware

Go to givenergy.cloud → My Inverter → Software. The current firmware version is shown here.

Battery firmware

Battery firmware version is visible in the portal under My Inverter → Battery details. GivEnergy Ltd entered administration on 9 April 2026, so the firmware compatibility matrix is no longer published or maintained. Send us both version numbers and we will check them against the pairings we hold.

Please don't update from the portal or app

We no longer advise owners to run firmware updates themselves from the GivEnergy portal or app. We have seen faults start after a self-service update. STS does firmware updates manually, to our own written procedures, with the right file for your inverter and battery: on a callout, or by talking you or your electrician through it remotely. If the versions don't match, contact us and we will tell you what is needed before anything changes.

Update already running? Red and green flashing together on the battery or inverter means a firmware update is in progress. Leave it alone and do not switch anything off, even if it seems slow. If it still hasn't finished after an hour, contact us before you touch anything.

Battery firmware: on a callout or guided remotely

Battery firmware is written to the USB drive inside the battery, behind the front cover. That means opening the front cover of the battery, so do not attempt it on your own. GivEnergy Ltd is in administration and no longer issues firmware to owners. STS holds the GivEnergy firmware. We can do the update on a callout, or supply the right file and talk you or your electrician through it remotely. We do not publish the files, and you should not use firmware from any other source.

Safety: Battery local firmware updates involve isolating the DC MCB and opening the battery enclosure. This is live electrical equipment: the cells inside stay live even with the system switched off, so with the cover off only the USB drive is touched. Do not attempt this unguided: we do it on a callout, or stay on the call with you or your electrician for every step. The GivEnergy support desk closed with the administration, so there is no address left to request the file from. If a battery firmware update is genuinely needed, book it as a job: the engineer brings the correct file, or we send it to you or your electrician before the call.
Cause 4
BMS protection event

BMS protection event: the battery has locked itself out

The battery management system (BMS) can lock the battery into a protection state after events like over-voltage, under-voltage, over-temperature or a short circuit. While it is in protection, the BMS stops answering the inverter. That is logged as BMS Comm Fail even though the cable is fine.

What triggers a BMS lockout

→Over-discharge: the battery ran below its minimum voltage, often after a long power cut with EPS running
→Over-temperature: the battery is in a confined space with poor ventilation, particularly in summer
→Charge voltage spike: the inverter sent the wrong charge voltage during a firmware update or a settings change
→Cell imbalance: individual cells have drifted well apart, triggering a BMS protection shutdown

Telling a BMS lockout from a cable fault

→Check the event log for protection events just before the BMS Comm Fail event. Over-voltage, under-voltage or temperature warnings are the key signs
→Look at the battery status light and note the colour. Solid red means a battery fault that needs investigating. Amber or yellow points to the BMS not talking to the inverter. Flashing red on a Gen 1 or Gen 2 battery means very low charge
→Check the battery temperature if you can: batteries in garages can overheat in summer
→Did the fault start during a power cut? EPS running until the battery is flat is a common lockout trigger

Recovery from BMS lockout

Some BMS protection events clear after a controlled restart (see the power cycle section above). Others, particularly over-discharge events, need the battery recovering with a slow charge before the BMS will accept normal operation. There is no GivEnergy support desk to escalate this to since the administration. If a restart doesn't clear the fault and a BMS protection event is suspected, your installer is the right first call if they are still trading, or we can review the event log remotely.

See the red status light guide →
Cause 5: last resort
Hardware

Hardware fault: the inverter's battery comms port or the battery's BMS board

If all the above have been checked and ruled out, the fault may be a hardware failure: either the battery comms circuit on the inverter, or the BMS board inside the battery. These used to be manufacturer warranty repairs. GivEnergy Ltd entered administration on 9 April 2026 and the administrator has said no further hardware warranties will be honoured, so that route is effectively closed.

Inverter comms port failure

The battery comms circuit on the inverter's board can fail, particularly after lightning surges or sustained over-voltage events. Signs include a persistent BMS Comm Fail with a known-good cable, and the fault still showing when a different battery is connected as a test.

Inverters installed from 11 September 2023 carried GivEnergy's 12-year warranty. Before that, inverters had 5 years, or 10 years if an extended warranty was paid for: your paperwork shows which. A direct claim against GivEnergy Ltd is unlikely to succeed now it is in administration. Your installer's workmanship cover, an insurance-backed guarantee, Section 75 or MCS Consumer Code redress may still be open to you. Our warranty page walks through each route.

Battery BMS board failure

The BMS board inside the battery can fail independently of the battery cells. This is a hardware fault inside the enclosure and requires an engineer visit. Do not open the battery yourself. Batteries installed from 11 September 2023 carried GivEnergy's 12-year warranty, and earlier ones 10 years at 70% capacity, but GivEnergy Ltd is no longer honouring hardware warranties.

A written engineer report identifying the fault is what any remaining route will ask for, whether that is your installer, an insurance-backed guarantee or a Section 75 claim. Be realistic about the money too: on an older battery a BMS board replacement is not always economic.

We provide written diagnostic reports

GivEnergy Ltd is no longer honouring hardware warranties, but a written engineer report identifying the fault type and cause is what your installer, an insurance-backed guarantee or a Section 75 claim will ask for. We can provide it as part of a remote diagnostic session.

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Related GivEnergy pages
Red status light

What a red light on the battery or inverter means, and what to check next.

See red status light →
Firmware updates

Firmware updates causing new faults or resetting settings.

See firmware updates →
Battery not charging

Battery not charging overnight: Timed Charge window and CT clamp causes.

See battery not charging →
GivEnergy fault codes

Full index of GivEnergy fault codes and their meanings.

See GivEnergy fault codes →

This is a brand-specific version of our general battery communication fault guide, which covers all brands.

FAQ

GivEnergy BMS Comm Fail questions

STORAGE_WARN_BMS_COM_FAIL is a warning. The inverter has had trouble talking to the battery's BMS (battery management system) but has not lost it completely. The battery may still be working, but the inverter can no longer fully trust what the BMS tells it. Try a battery-only restart first. STORAGE_ERROR_BMS_COM_FAIL is the error version and means communication has been lost. Both point to the same causes. The error version means the fault has lasted longer or is more severe.
Yes. Solar generation is usually unaffected. The panels and inverter keep generating and export or supply the house. What stops is battery charging and discharging, because the inverter cannot safely run the battery without the BMS link. Your solar figures in the portal should still be accurate. Solar carrying on while the battery drops out of the portal is a good sign the problem is communication, not power.
A fault that clears after a restart but returns within hours or days usually points to one of three things: a cable that is not fully seated and works loose, a firmware mismatch where the inverter and battery connect at start-up but lose each other during operation, or a BMS protection event that keeps triggering. A remote diagnostic that reviews your event log over the past week can spot the pattern and narrow the cause.
In a stack, each battery has its own BMS. On LV systems every pack needs its own dip-switch address and a fully seated cable. On HV kits the packs share a CAN chain that needs its terminator in place. If one pack drops out while the others are fine, start with that unit: is it switched on, is its cable fully home, and is its firmware compatible with the others? GivEnergy's Gen 3 battery manuals say all batteries must be on compatible firmware. The address and firmware checks are engineer jobs, so send us what you see and we will check remotely first.
The remote diagnostic is free. Tell us what the app or portal shows and we'll review your event log at no charge. If the fault is something we can put right remotely, such as a settings correction, the fix is a flat £125. If we can't fix it remotely, there's nothing to pay. If the log points to a physical fault, such as a damaged comms cable, a failed BMS board or a damaged inverter port, that needs an on-site visit quoted up front from £295 before anyone comes out. You'll always know the price before any work starts. Full pricing →
We can look at most BMS Comm Fail cases the same day. Once you send the event names and roughly when they appeared, we review your event log remotely. If it's a settings issue we can often put it right in that session, then allow 5–10 minutes for the inverter and battery to re-establish communication. If the firmware versions don't match, we do the update to our own procedures, either on a callout or by talking you or your electrician through it remotely. If the log shows a loose cable or a BMS hardware fault that needs hands-on work, we'll book the earliest on-site slot rather than leave the battery offline. Either way you get a written report. GivEnergy Ltd is in administration and is not honouring hardware warranties, so that report is for your installer, an insurance-backed guarantee or a Section 75 claim rather than the manufacturer.
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