ARCO Zeus + Orion XS + Cerbo GX (DVCC) – Zeus charging current not included in battery balance

Right, so I've been scratching my head over this one for a good few weeks now, sat on the cut wondering why my battery SOC keeps drifting into fantasy land.

Here's my setup aboard the boat:

• Victron Cerbo GX with DVCC switched on
• Victron SmartShunt as the main battery monitor
• ARCO Zeus managing the alternator, with its own ARCO shunt
• Victron Orion XS handling the DC-DC from the engine battery

The problem is this: the SmartShunt knows precisely nothing about the current the Zeus is pushing in from the alternator. The Orion XS plays nicely — shows up in the Cerbo, current gets counted, lovely. But the Zeus? Invisible to the battery balance calculations. My SOC readout ends up looking like it was estimated by a slightly optimistic golden retriever.

I think the issue is that the ARCO shunt isn't communicating its figures back into the DVCC loop properly, so the Cerbo just... ignores it. The Zeus charges away merrily whilst the SmartShunt thinks the battery is sitting there doing nothing.

Has anyone else run into this particular headache? I'm curious whether:

1. There's a VE.Bus or VE.Direct trick I'm missing
2. The ARCO needs configuring differently to report into the Victron ecosystem
3. Or whether physically repositioning the SmartShunt to catch all incoming current is just the sensible fix

Would love to hear from anyone running a similar hybrid alternator setup — especially on a narrowboat or off-grid build where the alternator is doing the heavy lifting most of the day.

@BoxerWanderer classic narrowboat gremlins 😄

Sounds like your Zeus isn't reporting its charge current back through the VE.Can/VE.Bus chain properly, so the Cerbo's DVCC charge current balancing is basically doing maths with a missing number. Not ideal when you're trying to keep SOC honest.

Few things

@BoxerWanderer the Cerbo's basically doing GCSE maths with one hand tied behind its back — if the Zeus isn't on the VE.Can/VE.Direct chain reporting current, the battery monitor has no idea it's even there and your SOC calculation is about as accurate as a chocolate sundial.

Seen this exact nonsense in my cabin setup; fixed it by making sure DVCC's "Shared Current Sense" is properly enabled and that the Zeus is actually recognised as a charger input in the device list — not just sat there looking decorative.

Check Settings → DVCC → SVS/SCS on the Cerbo and see what's actually contributing to the measurement. Fogstar's documentation on this is decent if Victron's own manual puts you to sleep, which it will.

@MultiPlusNerd nailed the metaphor but the fix is dead simple — shove a proper BMV-712 or SmartShunt on the battery negative and let the Cerbo do its sums from actual measured current rather than whatever the Zeus fancies reporting that Tuesday.

@KentExplorer the SmartShunt suggestion is correct but worth being precise about where it goes — it needs to be the sole current measurement point for DVCC to work properly, meaning all loads and charge sources must sit on the load side of the shunt except the battery negative itself.

If the Zeus is wired such that its negative bypasses the shunt, DVCC's current-based SOC calculation is fundamentally broken regardless of what shunt you fit.

In my static caravan backup setup I had a similar issue with a Renogy DC-DC charger sitting outside the measurement loop. Moved the shunt to the true battery negative, configured it as the Battery monitor in Cerbo settings, and SOC drift resolved almost immediately.

@BoxerWanderer — post your negative busbar wiring diagram if you have one. That'll confirm whether it's a configuration issue or an actual wiring fault.

@Compo is right about placement being critical. Had almost identical grief on my narrowboat last summer — Cerbo was blissfully unaware of anything not on the VE.Can/VE.Direct bus.

One thing worth adding: once you've got the SmartShunt in the right position, make sure DVCC's SCS (Shared Current Sense) is actually enabled in the Cerbo settings. Without that ticked, the Cerbo won't use the SmartShunt's current reading as the authoritative source, and you're back to square one with the SOC drift.

Also double-check your SmartShunt's battery capacity and Peukert exponent are dialled in properly — default values are often way off for lithium setups, which compounds the inaccuracy significantly.