Swapped out my lead-acid leisure battery for a 200Ah Fogstar Drift LiFePO4 — worth the faff?

Been running a 2018 Transit-based motorhome for three seasons now, and last month I finally pulled the trigger on a Fogstar Drift 200Ah LiFePO4 to replace the tired 110Ah AGM that had been limping along since I bought the van. Total usable capacity has gone from roughly 55Ah (AGM at 50% DoD) to a genuine 180Ah usable, which is a transformative difference for two-person trips.

The install wasn't entirely plug-and-play. My existing Victron IP22 Blue Smart charger needed its charge profile tweaking — switched it to the lithium preset, absorption at 14.2V, float disabled entirely. Also had to sort the B2B charger situation because the factory split charge relay was clearly not going to cut it; ended up fitting a Victron Orion-Tr Smart 30A to handle alternator charging properly without hammering the van's charging system.

What I'm genuinely curious about is temperature management in winter. The Drift has low-temp cutoff protection built into the BMS, which is reassuring, but I've read mixed things about charging below 5°C in a poorly insulated locker. My battery lives in a vented under-seat compartment — not ideal for cold Welsh weekends in January. Anyone running LiFePO4 in similar uninsulated locations through British winters?

Also interested to hear whether anyone's paired a Fogstar Drift specifically with a Victron SmartShunt for accurate SoC readings — I've got one on order but wondering how long it takes to properly calibrate on a new lithium cell.

@VoltAlison yes absolutely worth it, done the same on my boat and honestly wish I'd done it years ago. The usable capacity jump is massive — you're not just gaining 90Ah on paper, you're actually using most of what you've got rather than babying it to 50%.

One thing though — did you sort your alternator charging properly? This catches people out. Standard transit alternator will just hammer into LiFePO4 without a decent DC-DC charger (Victron Orion is what I've got). Your AGM settings on the van's original system will not be right for lithium.

Also check your fusing is sized correctly for the higher potential discharge rates. Boring but important 🔥

@VoltAlison done the same swap in my cabin setup — Fogstar Drift is solid kit for the money. One thing worth checking is your B2B charger settings, the absorption voltage profile for LiFePO4 is quite different to AGM so make sure whatever's managing the charge from your alternator is actually configured properly. Easy to miss and you'll think everything's fine but you're not getting a full charge.

Also the BMS on the Drift handles a lot but it won't protect you from a dodgy fuse setup so worth reviewing that while you're in there anyway.

RetiredPlumber47 | 847 posts | ⭐ Trusted Member

@VoltAlison good shout on the Fogstar — decent bit of kit for the price point. One thing I'd flag from bitter experience: double-check your alternator charging setup. LiFePO4 will happily pull your alternator hard because the internal resistance is so low, especially when the battery's well depleted. Worth fitting a DC-DC charger (B2B) between the van's starter battery and the leisure bank if you haven't already. I use a Victron Orion on mine and it's been faultless.

Also worth mentioning — your existing battery monitor almost certainly needs recalibrating or replacing. The voltage curves are completely different from AGM so your state-of-charge readings will be nonsense otherwise. A proper Coulomb counter like the Victron BMV-712 makes a big difference to actually knowing what's going on.

How's your solar setup looking?

@VoltAlison the weight saving alone is worth celebrating — swapped lead-acid for LiFePO4 in my static caravan setup a couple of years back and the difference in how the system behaves is remarkable. Lead-acid always felt like it was sulking in the mornings; the LiFePO4 just gets on with it.

One thing nobody's mentioned yet — keep an eye on your charging profile. Your Transit's alternator will happily push the wrong voltage curve at the Drift if you haven't got a DC-DC charger (a Victron Orion-Tr Smart is what I ended up running). Without it you're not doing the battery any favours on longer drives.

Also worth noting the Drift handles cold reasonably well, but below about 5°C you'll want to watch charge rates — LiFePO4 and freezing temps aren't the best of friends.

ExpertWanderer | 312 posts | Transit owner

@VoltAlison great choice! One thing nobody's mentioned yet — keep an eye on your charging sources. LiFePO4 has a flatter discharge curve than lead-acid, so if your van-to-hab charger (B2B/VSR) was calibrated for AGM, it may not be pushing the Drift to a proper full charge. Worth checking the absorption voltage is hitting around 14.2–14.6V.

Also, if you're running a mains hookup charger, make sure it has a dedicated LiFePO4 profile rather than just bunging it on AGM mode — it'll still charge but you won't be getting the full 200Ah out of it long-term.

How are you finding the capacity in real-world use so far? I'd be curious whether the 200Ah is comfortably seeing you through a couple of days off-grid or if you're eyeing up solar to complement it.

@VoltAlison meanwhile my Renogy setup in the shepherd's hut has been quietly judging every lead-acid battery owner for two years — welcome to the cult.

Not to derail into static caravan territory, but the LiFePO4 journey is the same whatever the vessel. Moved my cabin over to a pair of Fogstar Drift 100Ah units last autumn and the thing that caught me off guard wasn't the performance — it was how boring it became. Previously I was constantly fussing over discharge levels, babying the AGMs through winter. Now the BMS just quietly handles everything and I've genuinely forgotten to worry about it. @VoltAlison that psychological shift is underrated. The faff is entirely front-loaded; afterwards it disappears.