Battery fuse blown = wrong voltage reported by LynxBMS

Has anyone experienced odd voltage readings from a Lynx Smart BMS after a battery fuse has blown?

Here's my situation. I've got a 24V system in my garden office build — two 200Ah lithium batteries wired in parallel, both running through a Lynx Distributor with individual fuses, feeding a Multiplus-II 24/3000. The whole lot is monitored via VRM and I'm generally pretty happy with it.

Recently one of the battery fuses blew (still not entirely sure why — possibly a connection issue I hadn't spotted). After it went, I noticed the BMS was reporting a voltage that didn't match what my SmartShunt was showing, and the Multiplus seemed confused about state of charge as well.

My questions are:

• Is this a known behaviour with the Lynx Smart BMS NG when one parallel string drops out? I'm wondering if it's averaging across both battery connections even when one is effectively dead
• Could the blown fuse cause the BMS to read a phantom voltage from back-feed through the remaining battery?
• Would replacing the fuse and doing a full VRM calibration sort it, or is there something else to reset on the BMS side?

I've had a look through the Victron documentation but couldn't find anything specific about this failure mode. The system is back running on a single battery for now with a current limiter set in VE.Config, but the voltage discrepancy is nagging at me before I put a fresh fuse in.

Anyone dealt with something similar, particularly on a parallel 24V setup?

@StuKnight yes, seen this exact thing. When a fuse blows on one of your batteries, the BMS is essentially reading a "ghost" voltage through the remaining cell balancing circuitry or the BMS communication wire rather than the actual bus voltage. It's not a Lynx fault as such — it's just measuring whatever it can still see.

Had something similar on my static van setup when a midi fuse went on one of my Fogstar Drift 100s. Victron Connect was reporting 26.8V when the actual bus was sat at 24.1V.

Worth checking:

• Which battery the blown fuse is on
• Whether the Lynx is still getting comms from both batteries
• Your actual bus voltage with a multimeter

Don't trust the BMS display until you've confirmed both batteries are properly back in circuit.

@StuKnight had almost the identical situation in my static caravan build last summer. Two Fogstar Drift 200Ah cells in a 24V setup, one fuse went quietly in the night and the Lynx was reporting some absolutely baffling voltages — looked like a brownout on the display but everything seemed fine.

The bit that caught me out was assuming the BMS readout was gospel. It isn't when the circuit's incomplete.

Worth checking a few things before anything else:

• Physically inspect every fuse in your Lynx Distribution unit
• Use a multimeter directly across each battery terminals, don't trust the BMS figure alone
• Check your Victron app history — you'll often see the voltage anomaly timestamped, which helps pinpoint when the fuse actually went

Once I replaced the fuse and had a full circuit again, the readings corrected themselves immediately.

Worth adding from a narrowboat perspective — voltage anomalies after a blown fuse are often worse to diagnose than people expect, because the Lynx Smart BMS can still appear to be communicating normally via VE.Can whilst reporting nonsense figures.

On my boat I had a similar head-scratcher last year. What actually caught it for me was cross-referencing the BMS voltage against the Victron BMV-712 — they disagreed by nearly 4V, which was the giveaway.

Before assuming it's a BMS fault, I'd methodically check:

• Each battery's fuse in the Lynx Distributor
• Confirm with a multimeter directly at the battery terminals
• Check VictronConnect for any historical alarms you might have missed

The BMS isn't necessarily faulty — it may simply be reading what it's actually seeing on that circuit segment.

@StuKnight yep, been there! Had a similar head-scratcher on my 48V setup — Victron Lynx BMS was reporting voltages that made no sense until I traced it back to a blown MEGA fuse on one of the cells.

One thing nobody's mentioned yet: check your BMS sense wires. If the voltage sense lead is on the "dead" side of a blown fuse, the BMS reads whatever phantom voltage is floating there. Completely misleads the whole system.

Grab a multimeter and probe directly at each battery terminal independently — don't trust the BMS readings until you've confirmed which fuse has gone. My Fogstar cells were absolutely fine once I sorted the fuse and re-zeroed everything.

Also worth checking your fuse rating is actually appropriate for your cable gauge. Under-rated fuses cause nuisance blows that are easy to miss.

Good shout from @RetiredEngineer86 — worth expanding on why this happens technically.

The Lynx Smart BMS derives its voltage reading from the sense wires, not the main busbars. With a blown battery fuse, you can end up with the BMS sensing through a partial circuit — sometimes via parasitic paths through the BMS comms or balancing circuitry itself. Result: a floating or wildly inaccurate reading that looks plausible enough to confuse you.

On my shepherds hut build I now run a separate low-current sense fuse (typically 5A) alongside the main ANL, so if the main fuse goes, the sense path fails cleanly rather than ambiguously.

Also worth checking: Victron's VE.Can network can propagate stale voltage data if the BMS drops off unexpectedly. Force a VE.Can rescan in VictronConnect before trusting any readings post-fault.