Internally powered self heating LiFePO4 Battery

Been looking into these for my van build and I'm genuinely torn on whether they're worth the premium.

The concept makes sense on paper — the battery draws from itself to warm the cells before allowing charge to flow, which should protect against lithium plating in cold conditions. But I keep coming back to the same question: how much capacity are you actually sacrificing to the heating element when you're parked up overnight in January?

I'm currently running a Fogstar Drift 100Ah and it's been fine down to about 5°C without any obvious issues, but I park in Scotland occasionally and last winter it got properly bitter. That's where I'd be nervous.

The Fogstar self-heating units look reasonable for the price, and I've seen a few people mention the Enjoybot ones as a budget option, though I'm not sure I'd trust an unknown BMS in a van environment with limited ventilation.

A few things I'm trying to work out:

• Is the self-heating circuit passive (only activates on charge) or can it run continuously to maintain temperature?
• Does the BMS cut off discharge as well when cells are too cold, or just charge?
• Are there any units with proper Bluetooth monitoring so you can actually see what's happening?

Victron obviously integrates well with everything but their LiFePO4 batteries are a completely different price bracket.

Anyone running one of these through a full UK winter? Would love to know if the real-world performance matches the spec sheets, especially for a van where temperatures can swing massively between day and night.

@JH_Power the self-heating draw is the bit that catches people out. In genuinely arctic conditions (-20°C overnight) you're burning capacity before you even start charging — could be 3-5% just to get cells to an acceptable charge threshold.

For van life that's often fine, because you're running a leisure load anyway and the parasitic draw is manageable. My concern with these units is the heating element reliability long-term — it's another failure mode baked into the pack.

Worth the premium? Depends entirely on where you're camping. Scottish Highlands in January? Probably yes. Surrey in November? Almost certainly not — a decent Fogstar or Fogstar Drift with proper insulation sorts 90% of UK use cases.

What's your typical worst-case ambient temperature? That's really the number that decides it.

@JH_Power had a similar dilemma before my last motorhome build. Ended up going standard Fogstar Drift cells with a separate heating pad wired through the BMS instead. Worked out cheaper and I could control exactly when heating kicked in via the Victron system.

The self-heating units make sense if you're genuinely wild camping in Scotland in January with no shore power to spare — but for most UK use cases it feels like paying a premium for maybe 3-4 weeks of weather per year where it actually matters.

What's your typical winter use pattern? If you're mostly on sites with hookup through the cold months, I'd honestly save the money and put it toward more capacity instead.

What's the real-world power draw like for the heating cycle though? That's the bit I can't find solid numbers on.

I've got a Fogstar 100Ah in my static caravan setup and last winter it was borderline useless below about 5°C without some external heat — so I get why these exist. But if the self-heating is pulling significant capacity just to wake itself up, that's got to compound in prolonged cold snaps?

Also curious whether any of the Victron kit plays nicely with the BMS on these — specifically the SmartShunt. Does it see the heating draw as normal discharge or does it confuse the SOC readings?

@RobJones85 which separate heater solution did you go with in the end? That might actually be the more sensible route for my garden office battery bank too — easier to size and control independently?

@OldSparky from what I've seen on the Epoch and Enjoybot units, you're looking at roughly 30-50W draw during the heating cycle, typically 15-30 minutes to go from -20°C to charge-ready — so worst case you're burning maybe 25Wh just to unlock the battery, which on a depleted pack starts feeling like a philosophical problem.

The daft irony is the colder it gets, the more energy the self-heating consumes, yet the less capacity you actually have available to fund it — my Victron BMV logs from last February were genuinely grim reading.

@RobJones85 's separate heater mat approach is arguably more efficient because you can run it off a small dedicated LFP buffer rather than cannibalising your main bank.

@OldSparky and @FormerCop — worth adding that the heating duration matters as much as the wattage. From what I've tested on my boat setup, a deeply cold battery (say -10°C) can take 20-30 minutes to reach charge-ready temps, so you're potentially burning through a fair chunk of your remaining capacity before you've even started topping up.

That said, for a van build like @JH_Power is planning, if you're regularly parking overnight in winter and want to plug into shore power first thing, the self-heating means the BMS won't block charging straightaway — which is the main practical benefit over a separate heating pad solution in my experience.