Quattro reading lower voltage on DC Bus

Anyone else noticed their Quattro drifting on DC bus voltage readings over time?

Mine's a 48/8000 and I've been running it for about 18 months as part of my emergency backup setup. Recently clocked that the DC bus reading in VRM is sitting around 0.2-0.3V lower than what my Victron SmartShunt and a calibrated multimeter both agree on. It's consistent, not random — always low by roughly the same margin.

What's odd is this wasn't happening when I first commissioned it. Seemed to creep in gradually.

Few things I've already ruled out:

• Cable resistance/voltage drop (terminals are tight, cables are properly rated)
• SmartShunt miscalibration (cross-checked with two separate meters)
• VRM display glitch (same reading via the Quattro's own display)

Wondering if it's a firmware thing — I'm not on the absolute latest build. Could also be thermal drift in the internal sense circuit, especially as the unit's been through a few warm summers in my outbuilding.

Not causing any immediate problems but it does mean the low voltage disconnect is triggering slightly earlier than it should relative to actual battery state. Running Fogstar Drift LiFePO4 cells so I'd rather the BMS and the Quattro are both working from accurate numbers.

Has anyone recalibrated via ESS or DVCC settings to compensate? Or is this more of a "send it back to a Victron dealer" situation?

Curious whether this is a known quirk with older Quattro units specifically — feels like something that'd be worth flagging in the community before it becomes a bigger issue.

Yeah seen this on mine. Few things worth checking before you assume it's the Quattro drifting:

• Battery cable terminations — loose lugs will drop your reading vs actual
• Shunt placement — if you've got a BMV or SmartShunt in the loop, calibration can skew things
• Firmware — VenusOS and Quattro firmware both affect how DC bus is reported in DVCC mode

My 48/5000 showed about 0.8V low vs my Fogstar cells' own BMS reading. Turned out my negative busbar connection had worked slightly loose after thermal cycling over winter.

Worth grabbing a decent multimeter and measuring directly at the Quattro DC terminals vs what VRM is reporting. If there's a consistent offset it's usually mechanical, not the unit itself going soft.

What's the actual discrepancy you're seeing? Matters whether it's 0.3V or 3V.

Worth noting that "drifting" and "reading lower" are two different things. Drifting implies it's changing over time, lower implies it's consistently offset from actual. Which is it?

Because the fix is different depending on which problem you actually have.

If it's consistently offset, check your VE.Bus cable length and whether you've got the DVCC settings configured properly in VictronConnect — I had a persistent ~0.3V offset on my garden office setup until I sorted that.

If it's genuinely drifting, that's more concerning and worth raising with your Victron dealer before the warranty clock runs out.

@GlenDoug makes a fair point about the terminology — worth nailing down what you're actually seeing before chasing ghosts.

One thing nobody's mentioned yet: where exactly is your Victron Battery Monitor getting its sense point from? On my motorhome setup I had a maddening period where my Cerbo was showing the Quattro's DC bus voltage rather than actual battery terminal voltage, and the two disagreed by nearly 0.4V under load.

Turned out I'd bodged the shunt position during a rushed rewire on a campsite in the Brecon Beacons — not my finest hour, I'll admit.

If your DVCC settings are pulling voltage sense from the wrong device, you'll see exactly this symptom. Check your VRM and confirm which device has the active voltage sense role in the ESS assistant config.

@GlenDoug is right but also — had mine reading 1.2V low on my boat install and it was just a dodgy shunt connection giving the Quattro false data to argue with itself about 🙃