Smartshunt phantom currents and power company transformer

Interesting one this — has anyone else experienced phantom current readings on their Victron SmartShunt?

I've noticed occasional oddities on my shepherd's hut setup where the shunt reports small but persistent draws that don't match what's actually running. Nothing as dramatic as 22A for 48 hours, but enough to make me question the state of charge readings.

A few things I'm wondering about:

• Could interference from the nearby grid transformer (there's one about 30 metres from the hut) be affecting the shunt's measurements?
• Is it worth checking the grounding arrangement first before assuming the shunt itself is faulty?
• Has anyone tried repositioning their shunt or adding ferrite cores to the data cable to reduce noise?

My setup uses a Fogstar Drift 100Ah lithium with the SmartShunt mounted close to the negative terminal, all connected via the Victron app over Bluetooth. Everything looks right but I occasionally get phantom loads appearing overnight when nothing is switched on.

I've read that poor earthing or even a dodgy neutral on the mains side can induce small currents that confuse the shunt — is that plausible on a completely off-grid system, or am I overthinking it?

Would be curious whether anyone on here has traced similar gremlins back to external electrical infrastructure rather than a wiring fault in their own system. Particularly interested if you're on a rural supply where the transformer might be older or less well-maintained.

@CamperClive — almost certainly transformer-coupled noise from the grid supply if you're anywhere near a DNO substation or running a long earth cable.

On my narrowboat I had phantom readings of ±0.3A on the SmartShunt when moored at a marina with dodgy shore power. Turned out to be common-mode noise riding the negative bus.

Few things worth checking:

• Single-point earthing — are all your negatives bonding at one point only?
• Shunt placement — must be the only path between battery negative and system negative
• VE.Direct cable routing — keep it away from AC wiring, even a few centimetres helps enormously
• Check your zero current calibration in the VictronConnect app with everything genuinely disconnected

The SmartShunt's synchronisation threshold (default 0.10A) can also mask or exaggerate this depending on settings. Worth bumping it slightly if genuine phantom drift is confirmed.

@CamperClive oh mate, I had exactly this nonsense in my van build last spring. Parked up near one of those big green DNO boxes overnight and my SmartShunt was insisting I was simultaneously charging AND discharging at 0.3A. The battery just sat there looking confused, same as me.

Turned out my negative cable run was acting like a lovely little antenna. Rerouted it closer to the chassis and twisted it with the positive — phantom readings basically vanished.

Worth checking your shunt's ground reference too. If the shepherd's hut has any grid-tied equipment nearby sharing earthing infrastructure, you can get genuinely weird induced currents that aren't entirely "phantom" — they're just tiny and real and annoying.

@RustySpanner is on the money about transformer coupling though. Distance from the substation matters enormously.

Great thread this — @CamperClive I'd add that it's worth checking whether the phantom readings correlate with time of day. In my shepherd's hut I noticed the oddities were worst in the evening when local demand peaks, which pointed squarely at transformer loading rather than anything wrong with the shunt itself.

Worth also verifying your shunt's ground reference is solid — a loose or corroded negative connection can make the shunt "see" noise it shouldn't. Clean the terminals and check torque on those M8 bolts.

@RustySpanner makes a fair point about DNO substations, but honestly even a standard street transformer a few hundred metres away can cause this if your earthing isn't up to scratch. The SmartShunt is quite sensitive by design.

Try the Victron Connect app's history screen — if the phantom currents aren't showing up there, it may just be a display glitch rather than genuine noise pickup.

@CamperClive worth checking your shunt's negative terminal connection quality first before chasing transformer noise. I had a similar thing on my LiFePO4 setup — turned out to be a slightly loose ring terminal causing intermittent resistance variations that looked like phantom loads on the Victron app.

Also, if you're running the SmartShunt alongside any inverter/charger on the same bus, switching noise from the inverter can bleed through. Victron's own guidance suggests keeping the shunt wiring away from high-current AC cables.

What's your synchronisation interval set to in the app? Dropping it helped me filter out some of the spurious readings — though it does increase Bluetooth traffic. The Fogstar Drift cells I'm running are pretty transparent to this sort of noise so I can rule out the battery side being the culprit in my case.