Victron BMS keeps throwing a low cell alarm but the cells look fine on my meter

Had this exact faff with my van build last spring — turned out my meter was lying through its teeth while the Victron was picking up a genuine voltage sag under load that the meter couldn't catch fast enough.

A few things worth checking:

• Cell-level voltage under load, not just at rest — static readings are basically useless for spotting the weak sibling in a pack
• Balance wires — a dodgy connection on one sense wire will have the BMS convinced a cell is tanking when it's absolutely fine
• BMS alarm threshold settings in VictronConnect — the default low cell alarm can be very twitchy, and winding it back 50–100mV sometimes sorts the false alarms without masking a real problem
• Cell age and internal resistance — even if they're reading correct voltage, a cell going high-IR will sag under any meaningful draw and recover instantly, making it look fine two seconds later

My Fogstar cells threw similar phantom wobbles until I tightened every balance lead connector — embarrassingly simple fix after three weeks of head-scratching.

Worth grabbing the Victron Battery Protect data logs too if you haven't already, because the history tab will show you whether it's a consistent cell or a random rotating alarm, which tells you a lot about whether it's a wiring gremlin or a genuinely dodgy cell.

Anyone else had the balance wire culprit situation? Feels like half this forum's diagnostic threads end there eventually. 🔧

@RiverFinn that's a really useful distinction — static voltage vs voltage under load.

I had something similar crop up on my static caravan setup. Multimeter was showing all cells healthy sitting there doing nothing, but the Victron was catching brief sags when the inverter kicked in. Classic dynamic vs static reading problem.

Worth checking — are you measuring cells with any load actually running? Even something modest like a 12v fan connected while you probe each cell individually can reveal a weak one that looks fine at rest.

Also curious what cell chemistry you're running? I've read that LiFePO4 cells can mask weakness better at rest due to the flatter discharge curve compared to other lithium chemistries. Would make a dodgy cell harder to spot without load testing.

@RussWebb the meter sees the polite Sunday-best voltage, the BMS sees what happens when you actually ask the cells to do something — massive difference, especially if you've got dodgy internal resistance creeping in on older cells.

@FellGraham "Sunday-best voltage" is going in my vocabulary permanently — my Fogstar cells do exactly this, pristine on the meter then absolutely falling over themselves the moment the garden office kettle kicks in 🫖

@FellGraham "Sunday-best voltage" is brilliant but my static caravan cells are more like Monday morning before coffee voltage — technically alive, deeply unimpressive under any actual demand.