Anyone else had a Victron MultiPlus trip on a cold morning when the Fogstar batteries were below 10°C?

Mine did it twice last week — MultiPlus 12/3000 just threw a low battery alarm at 07:00 both times, even though the Fogstar Drift 200Ah was sat at a perfectly respectable 13.1V resting voltage. Turned out the BMS was throttling charge/discharge current because the cells were cold, so the inverter saw a voltage sag under load and panicked.

Fixed it (sort of) by bumping the DC input low shutdown down to 11.5V and adding a tiny 10W heat mat under the battery, but it feels like a bodge rather than a proper solution — surely there's a smarter way to handle this with the DVCC settings in VE.Configure?

Wondering if anyone's dialled in a low-temp cutoff workaround that doesn't involve babysitting the app every frosty morning.

CraigDavies | 847 posts

@BrookLover classic cold morning BMS issue, this. The Fogstar Drift has low-temperature charge protection built in, and if the cells drop below around 5-10°C the BMS will disconnect to prevent damage. The MultiPlus then sees that sudden disconnection as a low battery event rather than a BMS cutout — hence the alarm despite a healthy resting voltage.

Worth checking your Fogstar app (if you've got the Bluetooth module) to see what cell temps were logged at that time.

The fix most people land on is either a small battery heater wrap, or if you're using Venus OS, setting a low-temp cutoff offset in the DVCC settings so the MultiPlus backs off gracefully before the BMS pulls the plug. What's your installation situation — shed, vehicle, static cabin?

ZoeBurns | 312 posts

@BrookLover worth checking whether it's actually the charging side causing the trip rather than discharge. The Drift's BMS will cut charge current below 5°C, but if your MultiPlus is set to bulk charge early morning and the battery rejects it, the voltage can spike oddly and confuse things. Had something similar with mine over winter.

What's your absorption voltage set to in VictronConnect? I dropped mine to 14.2V during colder months which seemed to smooth things out. Also — and this sounds obvious — have you got a temperature sensor fitted? The MultiPlus really does benefit from proper battery temp compensation rather than guessing. The Cerbo GX with a Smart Battery Sense transformed how mine behaved through January. @CraigDavies is right about the BMS, but there's usually a tuneable fix before you start pulling your hair out!

LochSeeker | 1,204 posts

Had almost identical with my MultiPlus 2 last winter — worth checking your battery temp sensor is actually connected and configured in VictronConnect. If the MultiPlus isn't seeing a temp reading, it can't apply the low-temp charge disconnect properly and things get a bit unpredictable.

Also @BrookLover, have a look at your DC input low shutdown voltage in VEConfigure. Cold LiFePO4 cells sag more under load, so even at 13.1V resting you might be hitting the shutdown threshold momentarily when the inverter pulls a decent load at startup — kettle going on, heating kicking in, that sort of thing.

What's your DC input low shutdown currently set to? Default Victron settings aren't always ideal for lithium.