Quattro Firmware Update using VRM with BMS

Been meaning to post about this for a while after going down a rabbit hole on it last month.

I've got a Quattro 5kVA running in my garden office setup alongside a Fogstar Drift 200Ah with the BMS connected over CAN bus. Went to push a firmware update through VRM and got myself in a proper mess — the update seemed to stall and I wasn't sure if it was the BMS connection causing grief or just flaky internet on my end.

Did a bit of digging and it seems there's a known issue (or at least a was known issue) where having a BMS on CAN bus active during a firmware flash can cause problems. Whether that's still the case on more recent VRM firmware I genuinely don't know.

My question for the thread: has anyone successfully updated Quattro firmware via VRM with a BMS CAN bus connection still active? And does bypassing that by using a direct MK3-USB connection actually sidestep the problem entirely, or does the BMS presence still cause issues regardless of update method?

I ended up disconnecting my BMS comms temporarily and doing it via MK3 direct, which worked fine — but that's not always practical, especially if you've got a more complex system or the kit is mounted awkwardly.

Would be good to get a clearer picture of where things stand currently. Victron's documentation on this feels a bit patchy and the VRM changelog doesn't exactly spell it out.

Anyone else hit this? Particularly curious if others running PACE or Daly BMS units have had different experiences to those on Pylontech.

DustyBodger | Posts: 847

@LisaHunt88 Looks like your post got cut off there - you were just getting to the interesting bit about the BMS connection!

I've done a few Quattro firmware updates via VRM remotely and the BMS interaction is definitely something worth being careful about. The main thing I'd flag is making sure your DVCC settings are sorted correctly beforehand, otherwise the update process can occasionally cause the BMS to throw a wobble and disconnect at an awkward moment.

What firmware version are you coming from and going to? There were some fairly significant changes around the 490-500 range that affected how the Quattro handles BMS communication.

Finish your original post and I'll try to help properly - curious whether you're using the Fogstar's CANbus output or just VE.Bus. Makes a difference to how you approach it.

@LisaHunt88 yeah, finish that post! Guessing you hit the BMS comms drop issue during OTA update via VRM?

Classic gotcha with the Quattro + Fogstar Drift combo. The BMS talks over VE.Can or VE.Bus, and mid-firmware-flash the GX device briefly loses comms — some BMS units interpret that as a fault and pull the charge/discharge enable lines. Result: update bricks partway through.

The safe way to do it:

• Disconnect the BMS communication cable before initiating the VRM remote firmware update
• Keep the DC connected obviously, you need the power
• Update completes cleanly, GX reboots, then reconnect BMS comms

Done this on my narrowboat's Multiplus II setup twice without drama. The Victron VRM remote update process itself is solid, it's just the BMS handshake timing that catches people out.

What firmware version are you jumping from/to? Some of the older 490-series builds had quirks worth knowing about.

RustyTinker | Posts: 312

@LisaHunt88 Done exactly this on my motorhome Quattro 48/5000. The short version: during a VRM remote firmware update, the Quattro briefly drops its charge algorithm and the BMS can interpret that as a fault condition — cuts comms, sometimes trips the battery disconnect entirely.

What worked for me was setting the DVCC charge current to a conservative figure beforehand, and making sure the BMS was in a relaxed state of charge — mid-range, not near limits. Reduces the chance of it getting twitchy during the handshake interruption.

Also worth checking your VE.Bus firmware version before you start. Some older versions make the transition rougher than it needs to be.

Would be useful to know which BMS firmware your Fogstar Drift is running. That matters more than most people realise.

MarinePhil | Posts: 1,204

@LisaHunt88 Looks like we've got two cut-off posts here which is frustrating — @RustyTinker you too!

The key thing people miss with VRM remote firmware updates on a Quattro when a CANBUS BMS is in the loop: the BMS can interpret the inverter dropping to update mode as a fault condition and disconnect the battery entirely, which kills the update mid-flash. Nasty situation.

What saved me on my van build was:

• Pre-charging a separate small AGM as a keep-alive on the Cerbo GX
• Setting BMS charge/discharge enables to manual override beforehand via the console
• Doing it during daylight with solar maintaining bus voltage

Victron's own knowledgebase is surprisingly thin on this specific scenario. The Fogstar Drift BMS in particular can be twitchy — worth checking your DVCC settings are locked before you start.

LiFePO4Nerd | Posts: 847

The bit nobody warns you about: your BMS will almost certainly drop the VE.Bus comms mid-flash if it decides the Quattro's behaviour during firmware upload looks like a fault condition. Seen it on my own Victron/Fogstar setup.

My fix — disconnect the BMS communication cable before initiating the VRM remote firmware update, leaving the battery connected purely for power. Let the flash complete fully, then reconnect comms and let everything re-handshake.

Some folks swear by doing it via MK3-USB locally instead, which gives you far more control over the process. Honestly for anything critical I'd still prefer local over OTA, VRM remote updates are convenient but you're one dodgy mobile signal away from a bricked unit.

@RustyTinker curious whether your motorhome setup gave you the same BMS dropout or something different — would help @LisaHunt88 build a clearer picture.