Lynx Shunt fiel aus und nun passt die Strommessung nicht mehr

Had a similar headache last year on the boat. Running a pair of Multiplus II 48/5000s through a Cerbo GX, and when my Lynx Shunt started playing up after a saltwater ingress incident, the whole current measurement picture went completely sideways.

The Cerbo was reporting SOC figures that made no sense — showing 80% whilst the batteries were clearly struggling under load. The Fogstar Drift cells I'm running deserve better than that kind of guesswork, especially when I'm also trying to manage EV charging from the system at the cabin.

What I eventually traced it to was the shunt's calibration having drifted rather than a full failure. Victron's support suggested doing a full synchronisation after replacing the unit, but the key thing nobody mentioned upfront was that all three phases need to be stable and balanced at the point of sync, otherwise you're just baking the error in permanently.

A few things worth checking if you're in a similar situation:

• Is the VE.Direct connection between the shunt and Cerbo solid? Mine had developed intermittent dropouts I'd missed
• Have you tried forcing a manual SOC sync via the Cerbo touchscreen?
• Check whether your ESS assistant settings are fighting the shunt readings — mine were, which masked the real problem for weeks

Curious whether anyone else running multiple Multiplus units on a single Lynx bus has seen measurement drift rather than outright failure. Feels like it's more common than Victron's documentation suggests, particularly in marine environments with vibration and humidity thrown into the mix.

@DaiHenderson saltwater ingress into a Lynx Shunt is basically a death sentence for accurate current measurement — the shunt resistance itself can corrode and drift, so even after drying out, your calibration figures are meaningless.

Before replacing the unit, worth checking a few things in VictronConnect:

• Shunt current vs what a clamp meter reads on the same conductor simultaneously
• Whether the Peukert exponent and charge efficiency factor have wandered off defaults
• Cross-reference the Cerbo's readings against any secondary monitoring you've got

In my garden office setup running a Multiplus II 48/3000 with a Lynx Distributor stack, I've found even minor resistance changes at the shunt connections cause wild SOC drift within days.

Realistically, if it's had a saltwater soak, just replace the shunt — Fogstar and many dealers stock them and they're not catastrophically expensive relative to the headache of chasing phantom readings.

@DaiHenderson mate, saltwater and Victron kit go together about as well as a damp fuse box and a cup of tea — replaced my Lynx Shunt after a dodgy calibration drift in my garden office setup and the Cerbo GX was showing me numbers that made my battery bank look like it was running a small nightclub.

Quick tip: before you bin it, check the shunt's calibration offset in VictronConnect — sometimes a full reset to factory defaults sorts the daft readings without needing a replacement.

If it's properly cooked from the saltwater though, a new unit is around £180-£200 from the usual UK suppliers and it's genuinely plug-and-play with the Cerbo once you've done the setup wizard properly.

@DaiHenderson been there, done that, got the corroded shunt to prove it. After my Lynx Shunt threw a tantrum on my narrowboat, I discovered the fix isn't just swapping the unit — you must do a full battery monitor reset on the Cerbo GX afterwards, otherwise it inherits the drifted calibration values like some sort of cursed heirloom.

Go into Settings → System Setup → Battery Monitor and reassign the shunt fresh. Also worth checking your VE.Direct cable terminals while you're in there — saltwater loves creeping along cable runs.

On the replacement front, Fogstar now stock the Lynx Shunt at decent prices if Victron's official route feels steep. Once my readings settled, I ran a proper charge/discharge cycle to let the SOC algorithm relearn — took about two days but accuracy came back beautifully.

@DaiHenderson worth checking whether the shunt calibration offset has drifted in the VRM/Cerbo settings even after replacing the unit — saltwater ingress can corrupt the stored calibration values that persist in the Cerbo itself, not just the shunt hardware. Had exactly this on my narrowboat last summer; fitted a brand new Lynx Shunt but the SOC readings were still wildly off until I did a full BMV calibration reset through the remote console and let the system run a proper charge/discharge cycle to re-establish the floor.

Also double-check your cable torque on the busbars afterwards — corrosion tends to spread further than you'd expect, and a slightly loose connection post-cleanup will give you spurious current spikes that look like a faulty shunt but aren't.