SmartShunt and Venus OS disagree on 100% SOC

Been having a similar head-scratcher on my boat setup and wondering if others have run into this.

My SmartShunt is syncing to 100% fine — it's hitting the criteria I've set (absorption voltage sustained, tail current dropping below threshold, charge detection timer ticking through) — but when I look at the Venus OS dashboard on my Cerbo GX, the SOC figure shown there seems to lag behind or occasionally disagree with what the SmartShunt is reporting directly via the VictronConnect app.

A few questions I can't quite get my head around:

• Is Venus OS pulling the SOC value directly from the SmartShunt, or doing some of its own calculation on top?
• Could the discrepancy be down to a polling/update interval issue rather than an actual calculation difference?
• Has anyone found that tweaking the charged voltage or tail current percentage in the SmartShunt settings helps keep the two in better agreement?

My bank is 200Ah of Fogstar Drift LiFePO4, charged via a Victron MPPT and a B2B from the engine alternator, so there are occasionally two charge sources active simultaneously — wondering if that muddies the waters for the shunt's sync logic.

I've gone through the SmartShunt manual and it seems straightforward enough, but the Venus OS side feels like a bit of a black box in terms of exactly how it handles incoming SOC data from connected devices.

Anyone running a similar multi-source setup who's managed to nail this down? Interested to know whether this is a configuration issue or just something you have to accept as a minor quirk of the system.

@EwanCole58 had exactly this with my static caravan build last spring. The penny dropped when I realised Venus OS has its own tail current threshold baked into the DVCC logic — it won't declare 100% until it's satisfied, regardless of what the SmartShunt is reporting locally.

Worth checking two things:

1. DVCC settings on your Cerbo/Venus device — specifically the "SVS" and tail current values
2. Whether your SmartShunt's Bluetooth settings and the VE.Direct parameters are actually in sync, because I found mine had drifted after a firmware update

The fix for me was letting DVCC take full control and matching the tail current percentage across both. Once I stopped letting them "negotiate" independently, they agreed almost immediately.

Victron's own forum has a thread on this — search "SmartShunt SOC offset Venus" and you'll find the relevant dev response.

@EwanCole58 worth checking whether Venus OS is pulling its SOC from the SmartShunt directly via VE.Direct, or whether something else is feeding it. I had this exact split on my boat — turned out the MPPT was also connected and Venus was blending sources in a way that made no sense.

Go to Remote Console → Device List and check what's listed as the "battery monitor" under the system settings. If it's not explicitly set to your SmartShunt, Venus will make its own assumptions and they won't match.

Once I forced it to use the SmartShunt as the sole battery monitor source, both readings locked together. Took me an embarrassingly long time to find that dropdown.

Good shout from @RKE_Builds on the VE.Direct source question — that's the first thing to nail down.

One thing neither reply has touched on yet: Venus OS has its own synchronisation logic that can override or lag behind what the SmartShunt reports, particularly if you've got the "has DC system" toggle enabled in the CCGX/Cerbo settings. That box essentially tells Venus OS to calculate an additional DC load figure, which can skew the displayed SOC independently of what the shunt is measuring.

On my narrowboat I had a persistent 2-3% discrepancy until I audited every VE.Direct device listed under the "Devices" menu and confirmed Venus was actually consuming the SmartShunt SOC rather than calculating its own.

Worth checking: Remote Console → Device List → SmartShunt → SOC — does that figure match the Victron Connect app reading at the same moment?

Ran into this exact gremlin in my van last winter — sat there in a layby in the Peak District staring at two different numbers like I'd broken reality itself.

What nobody's mentioned yet: check your tail current threshold in the SmartShunt settings. If Venus OS is pulling SOC from the shunt via VE.Direct but the shunt's sync criteria include a tail current percentage, Venus can appear to lag because it's displaying a slightly smoothed/averaged value rather than the instantaneous sync moment.

In my case the fix was embarrassingly simple — the SmartShunt had synced, but Venus OS needed a full data refresh cycle before it caught up. Toggling the DVCC settings sometimes shakes it loose too.

Also worth a glance at whether your Fogstar or whatever cells have drifted — a sneaky capacity imbalance can make both devices technically "correct" but disagreeing. 😅