Lynx Shunt throwing Low Voltage alarms consistently - can’t find low voltage

Sorting out a mate's motorhome electrical setup and I've hit a wall with his Victron Lynx Shunt throwing Low Voltage alarms constantly, even when the batteries are clearly sitting at 26V+ on a multimeter.

His setup:

• 4x Fogstar Drift 200Ah cells wired in parallel (24V system)
• Lynx Shunt with two Lynx Distributors — one handling battery input, one feeding outputs to his Victron SmartSolar MPPT and a Votronic DC-DC charger
• All connected via Cerbo GX

The alarm fires sporadically, mostly when the DC-DC charger kicks in hard, but the actual bus voltage never dips low enough to justify it according to any other device on the network.

Few things I'm already suspicious of:

1. Voltage sense wiring — is the Lynx Shunt measuring voltage at the shunt itself rather than at the battery terminals? Could a volt or two of drop across dodgy busbars or connections be fooling it?
2. Alarm threshold misconfiguration — he's had a few people "help" him set this up and I wouldn't be surprised if someone set the Low Voltage alarm to something daft like 25.5V
3. Negative cable routing — all negatives returning correctly through the shunt, or has something been bypassed?

Before I start pulling everything apart, has anyone seen the Lynx Shunt behave like this when there's a high transient load pulling the bus voltage down momentarily — something too fast for a multimeter to catch but enough to trigger the alarm logic?

Worth grabbing a Victron SmartShunt alongside it

Paul1999 replied:

Classic one this - check your battery voltage sense wiring on the Lynx Shunt itself. If it's measuring voltage at the shunt rather than directly at the battery terminals, you can get a significant voltage drop across the busbars/connections giving false low readings, especially under load.

Also worth jumping into VictronConnect and checking what voltage threshold the alarm is actually set to trigger at - sometimes these come out of the box with settings more suited to a 12V system and nobody's rescaled them properly for 24V.

What does the shunt actually report as the voltage versus what your multimeter reads directly at the battery terminals? That'll tell you straight away whether it's a sensing issue or a configuration issue. Wouldn't be surprised if it's just the alarm threshold sitting at something daft like 22V.

@MarineGeoff 24V system but alarm threshold still set to 12V defaults — Victron doesn't auto-detect system voltage on the Shunt config, you have to manually set it in VictronConnect or it'll alarm at completely wrong thresholds all day long.

@MarineGeoff had almost identical drama on my boat last summer. The Lynx Shunt was screaming blue murder at me while the Fogstar batteries were sitting fat and happy at 25.8V.

Turned out my issue was the VE.Can termination resistors — one end of the network wasn't properly terminated, and the shunt was essentially reading phantom data. Worth pulling up the Network Status in VictronConnect and checking everything's talking properly before you chase your tail elsewhere.

Also worth double-checking which device is actually triggering the alarm in the notification history — sometimes it's not the shunt itself but a connected MPPT or MultiPlus on the same VE.Can network that's throwing the alert and it just looks like the shunt.

@MarineGeoff one thing nobody's mentioned yet — check whether the Lynx Shunt is actually measuring the right battery bank. On a 24V system with two 12V batteries in series, if the shunt's voltage sense is accidentally picking up across just one cell group, you'd see ~13V readings triggering low voltage alarms constantly despite the overall pack being healthy.

Also worth checking in VictronConnect: there's a "Low voltage alarm" threshold buried in the Lynx Shunt settings that's separate from your MPPT or MultiPlus thresholds. I've seen installs where someone's set it to something daft like 22V thinking they're being cautious, then forgotten about it entirely.

Had a similar head-scratcher on my own rig with Fogstar Drift cells — turned out to be a misconfigured alarm threshold that took me an embarrassingly long time to find. 🤦