Anyone else's inverter struggling in this cold snap we've been having?

Been noticing my Victron MultiPlus has been a bit grumpy this past week or so. Startup loads are taking longer to stabilise and I've had a couple of low voltage warnings that I wouldn't normally see at this state of charge.

Pretty sure it's a combination of things — the LiFePO4 cells on the boat don't love single-digit temperatures (Fogstar Drift 200Ah, about 18 months old), and the BMS is throttling charge acceptance first thing in the morning before the cells warm up. Means the inverter is leaning harder on whatever's already in the bank than it should be.

I've thrown an old blanket over the battery box as a stopgap which sounds ridiculous but seems to have taken the edge off. Probably should look at a proper insulated enclosure before next winter.

A few things I've been mulling over:

• Pre-warming the bank before heavy loads — basically running something small for 20 mins to generate a bit of internal heat
• Adjusting the low voltage cutoff thresholds slightly in VictronConnect to account for the cold sag
• Keeping SOC higher overnight as a buffer

Not sure if others are seeing similar. Anyone on a boat or in a similarly exposed setup dealing with the same? Curious whether this is purely a battery issue or whether the inverter itself is less efficient in the cold — I've read conflicting things on that front.

Also wondering if anyone's tried battery heating pads — worth it or overkill?

@TracyMitchell the low voltage warnings in cold weather are almost certainly your battery internal resistance increasing rather than the inverter itself. Lithium or lead-acid?

If lead-acid, you'll lose a significant chunk of usable capacity below 5°C — I've seen my bank drop to maybe 60-70% effective capacity when it's been genuinely bitter on the cut. With lithium (Fogstar, etc.) it's less dramatic but BMS protection can still throttle charge acceptance hard.

Worth checking your VRM dashboard if you're on Victron — look at the DC voltage under load rather than resting voltage. If it's sagging badly under startup loads that's your culprit.

Also — where's your battery bank situated? Mine's in the engine bay which helps enormously in winter. Exposed batteries in an uninsulated space will suffer.

@TracyMitchell your MultiPlus isn't grumpy, it's just British — performs perfectly fine until the temperature drops and then suddenly it wants a hot cuppa before doing any work 😄

Jokes aside, worth checking your battery terminals too. Cold has a sneaky way of making loose connections look fine while quietly robbing you of voltage under load

@TracyMitchell curious whether you're also seeing this affect your charge acceptance rates? I've been monitoring my setup (garden office system, Fogstar Drift LiFePO4) and noticed my BMS is throttling charge current noticeably below about 5°C — the cells just won't take it as fast.

Worth checking a few things methodically:

• What temperature is your battery bank actually sitting at? (Not ambient — the cells themselves)
• Are you running any battery heating, or is the bank in an uninsulated space?
• What does VRM show for your charge/discharge curves over the past week compared to a milder period?

I'm wondering whether the issue is primarily the battery side manifesting as inverter warnings, rather than the MultiPlus itself. @PennineNomad's point about internal resistance seems relevant here — do your warnings correlate with higher draw moments specifically?

@TracyMitchell worth checking what your MultiPlus's low temperature cutoff is set to if you haven't already — the default settings aren't always optimised for winter conditions and you might have a bit of headroom to tweak the absorption/float thresholds to compensate. Also, are your batteries in an uninsulated space? Even wrapping a bit of old sleeping bag or rigid foam insulation around them makes a surprising difference. Mine are in a shed and I knocked up a simple insulated box last winter — night and day difference. @PennineNomad is spot on about internal resistance too, which is why those startup loads are catching it out. What battery chemistry are you running? Makes a difference to how aggressively you can address it.

@TracyMitchell I've seen the exact same thing this week. Worth noting that it's not just the inverter — your battery internal resistance rises significantly in the cold, so even a healthy bank can't deliver current as cleanly. If you're running LiFePO4, the Fogstar cells I use drop noticeably in discharge performance below about 5°C.

What's your battery sitting at temperature-wise? If they're in an uninsulated space, wrapping them in a few layers of rigid foam insulation makes a real difference — brought my pack from hovering around 4°C up to 9°C overnight just from passive insulation alone.

Also worth bumping your absorption voltage up slightly in winter to compensate — Victron's VRM makes that easy to adjust remotely if you haven't already.