Anyone else finding their batteries struggling more than usual this winter?

Been noticing this myself over the past few weeks. The cabin setup (2x Fogstar Drift 200Ah in a 24V config with a Victron SmartSolar 100/30) has been genuinely struggling to recover during daylight hours when we get those solid grey days back-to-back.

The issue I keep coming back to is twofold:

1. Lower temperatures reducing usable capacity — lithium cells genuinely lose a meaningful chunk of capacity below about 5°C, even the better quality ones. My BMS logs are showing this clearly.
2. Pathetically short solar windows — we're talking 4-5 hours of genuinely useful irradiance on a good day right now, and that's assuming the panels aren't sat under a layer of frost or ice until 10am.

I've compensated by being more aggressive about load management — the 12V compressor fridge is the main culprit and I've wound the thermostat up a degree or two. Also started running any high-draw tasks (kettle, power tools) strictly around solar peak which in December feels like about a 90-minute window.

What I'd be curious to know is whether anyone with insulated battery enclosures is seeing meaningfully better results. I've been considering boxing mine in with some 50mm Celotex and adding a small PTC heater element on a thermostat, but I'm wary of thermal runaway risk if it's not done properly.

Worth also checking your battery interconnects and terminals for any resistance creep — cold weather can make marginal connections significantly worse and you'll see voltage sag that looks like capacity loss but isn't.

Anyone else got strategies they've found actually work rather than just theoretical fixes?

Yeah @OldSparky52 same boat here. Garden office setup took a proper battering last month — Fogstar Drift 100Ah just couldn't claw back what it lost overnight even on the brighter days.

Few things that helped me:

• Bumped my absorption voltage up slightly in Victron Connect (worth checking your temp compensation settings)
• Insulated the battery compartment — massive difference, LiFePO4 really hates the cold for charging
• Shifted as much load as possible to midday when the panels are actually doing something useful

The short days are the real killer tbh, it's not even temps so much as just minutes of usable solar. My shepherd's hut secondary setup is worse because it's more shaded in winter when the sun sits low.

Nothing revolutionary but the insulation thing genuinely surprised me how much it helped.

Similar story here with the garden office and cabin setups. Worth checking your charge absorption voltage hasn't drifted — I noticed my Victron SmartSolar had somehow reverted to default profiles after a firmware update, which knocked maybe 20-30% off effective capacity in cold weather.

Also, LiFePO4 cells genuinely lose usable capacity below about 5°C — Fogstar's own spec sheets acknowledge this. If your batteries are sitting in an uninsulated space overnight, you're starting each morning already behind.

Couple of things that helped me:

• Insulating the battery enclosure (even basic foil-backed foam made a difference)
• Setting a low-temp charge cutoff so you're not stressing cells when they're cold
• Adjusting MPPT absorption time upward slightly in the Victron app for winter months

The short days are brutal but the cold is arguably the bigger issue for recovery times.

Had this exact conversation with myself last November when the cabin setup went through a rough patch. Turned out the real culprit wasn't the batteries at all — it was panel angle. Dropped mine from 35° to about 55° for winter and recovered nearly 40% more usable generation on those low-sun days.

@OldSparky52 with a 100/30 you're already working with limited headroom. Worth pulling your Victron Connect history and checking what your actual peak input hours look like day-by-day. The data usually tells a grimmer story than you'd expect.

LiFePO4 chemistry handles cold reasonably well compared to lead-acid, but below 5°C the internal resistance creeps up noticeably. If your Fogstars are in an uninsulated space, that's worth addressing before anything else.

Same issue on the boat last December — turned out my MPPT was set to AGM defaults even though I'd swapped to lithium months prior. Completely wrong charge profile the whole time 😅

Worth double-checking your battery temp too. Fogstar Drift cells don't charge below 0°C and if you've not got a low-temp cutoff sorted, cold mornings could mean your controller is trying to push charge in and getting nowhere. The Victron BMV will show this if you dig into the history logs.

Also — shorter days mean your absorption window gets squeezed hard. Even a few extra watts of panel can make a surprising difference mid-winter.