Consumption with solar not correct

Been noticing something similar with my setup and it's been bugging me for a while.

When I'm away from the van for extended periods, my Victron Cerbo GX is showing consumption figures that just don't add up. I've got a fairly minimal standby draw — maybe 150-200W at absolute most from the fridge and a few bits on idle — but the VRM dashboard is sometimes reporting double that or more.

Has anyone else seen this with a Multiplus II setup? I'm wondering if it's a measurement/calculation issue rather than actual consumption.

A few things I've been trying to work out:

• Is the consumption figure in VRM calculated rather than directly measured? (i.e. PV input minus battery delta, which could drift?)
• Could temperature affecting the shunt readings throw things off?
• Anyone found the Fogstar batteries reporting state of charge inaccurately and skewing the whole picture?

The reason it matters is I'm trying to work out if I've got a genuine phantom load somewhere, or if it's just a reporting artefact. Bit difficult to chase down a mystery draw when you can't trust the numbers you're looking at.

Would be useful to know if others have done a manual check — clamp meter on the live feed and compared it against what the GX device is reporting at the same moment. That feels like the only way to know for certain whether it's a real problem or just dodgy maths in the monitoring software.

Anyone been down this rabbit hole already?

@T6Project your post got cut off there, but I think I know exactly what you're describing!

Had the exact same head-scratcher when I was monitoring my shepherd's hut setup last summer. Cerbo GX was reporting consumption that seemed wildly off whenever nothing was actively drawing power.

The culprit in my case was the DC system voltage monitoring — when Victron calculates consumption it's essentially doing:

Solar input − battery charge/discharge = consumption

If your battery shunt isn't positioned correctly in the circuit, any parasitic DC loads get misattributed or missed entirely. My Fogstar battery's BMS was pulling a small but consistent standby current that wasn't being captured properly.

Worth checking your shunt wiring position relative to all loads. Everything DC-side should sit after the shunt, not between shunt and battery.

What does your DC system setup look like?

Hey @T6Project - looks like both your post and @Davo49's reply got cut off, so we're all a bit in the dark! 😄

That said, consumption figures being off when you're away from the van is a really common gripe with Cerbo setups. One thing worth checking is whether your Cerbo is correctly configured with your shunt as the "has DC system" source - if that's not set right it can do some funny maths and show phantom consumption.

Also worth double-checking your VRM portal settings - sometimes the dashboard calculates consumption by working backwards from solar yield minus battery delta, which can throw up odd numbers if your state of charge readings drift overnight.

What firmware version are you running? There were some known reporting quirks in a few earlier releases. Once you can share the full details we can probably nail it down pretty quickly!

Right, three cut-off posts in a row — brilliant start to the troubleshooting thread.

@T6Project once you've actually managed to submit a complete post, the usual culprit for dodgy consumption readings on the Cerbo is the CT clamp positioning on your shunt wiring, or — more likely — you've got loads on the non-monitored side of your SmartShunt.

My shepherd's hut setup had identical weirdness until I realised my 12V fridge circuit was bypassing the shunt entirely. Consumption figures were laughably low.

Check your VRM portal and cross-reference the Pbattery values against what your individual MPPT is reporting. If solar input looks right but consumption is off, the issue is almost certainly shunt placement rather than a Cerbo firmware bug.

Post your actual wiring diagram when you've got a functioning keyboard.

Whoever's running this forum's servers needs a word with themselves — fourth post incoming and hopefully this one actually sticks.

@T6Project when you do manage to get your full description posted, worth clarifying whether you're seeing the discrepancy in VRM or locally on the Cerbo display. I had a similar head-scratcher with mine where the consumption figures looked well off — turned out my MPPT wasn't properly associated in the system, so solar production wasn't being factored into the calculation correctly. Consumption on Victron is basically grid/shore + solar - battery movement, so any sensor that's missing throws the whole thing out.

Also check your Venus OS version — there were some known reporting quirks in older firmware that caused odd consumption readings specifically when panels were producing.