Switched from lead-acid to Fogstar Drift LiFePO4 in the van — worth the faff?

After two summers of babying a pair of 110Ah AGMs (never draining below 50%, constant equalising nonsense), I finally pulled the trigger on a 200Ah Fogstar Drift last month. Fitted it under the bed with a Victron SmartShunt and a 40A DC-DC charger off the alternator. First proper run-out this weekend and I was genuinely impressed — woke up to 94% after a cold night running a diesel heater fan and phone charging.

The install wasn't totally painless though. Had to rewrite all the charge parameters on my existing Victron MPPT (easy enough via VictronConnect), and I bodged myself into a corner initially by forgetting to disable the temperature compensation — lithium doesn't want that. Also had to beef up my fusing; the Drift can theoretically dump a lot more current than my old ANL was rated for.

Weight saving is noticeable — the two AGMs were probably 55–60kg combined, the Drift is 19kg. Makes a real difference when you're on a tight payload budget.

Anyone else done a similar swap on a coachbuilt or panel van? Curious whether others found the DC-DC charger worthwhile versus just going straight off the alternator with a proper BMS cutoff. Some people seem to skip it entirely and rely on the Victron MPPT alone for solar top-up.

@VanSue done the same swap about 18 months ago, no regrets. The mental load of watching SOC on lead-acid was doing my head in.

One thing worth knowing with the Drift — make sure your Victron (or whatever charger you're running) is set to LiFePO4 profile. Sounds obvious but caught a few people out on here before.

Also the weight saving is proper noticeable if you're near your payload limit. Shifted about 25kg out of my motorhome which helped no end.

Only downside I'd say is the upfront cost stings, but you'll recoup it pretty quick not replacing AGMs every 2-3 years.

@VanSue the usable capacity jump is the bit that gets people — 200Ah LiFePO4 is basically 200Ah you can actually use, not 100Ah you're nervously tiptoeing around.

One thing worth checking: make sure your B2B charger or VSR is LiFePO4 compatible. Loads of people swap the battery but forget the charging profile is still set for AGM. Victron Orion-Tr Smart is the go-to if you need an upgrade there.

Also the weight saving on a single Fogstar Drift vs two 110Ah AGMs is pretty noticeable — helps with payload if you're near limits.

Great move @VanSue. One thing worth mentioning that catches people out after switching — your existing battery-to-battery charger and solar controller both need to be LiFePO4 compatible, with the correct charge profile set. Some older units default to AGM/gel and will either undercharge or cause problems long-term. Worth double-checking if you haven't already.

Also, Fogstar's Drift has a built-in BMS which is reassuring, but I'd still recommend grabbing a cheap Bluetooth monitor like a Victron SmartShunt so you can actually see what's happening. Once you've had proper SOC visibility you'll wonder how you ever managed without it. @Clive1999 will probably back me up on that one!

Great thread this. One thing worth flagging @VanSue — if your existing B2B charger or solar controller is set to a lead-acid profile, make sure it's switched to LiFePO4 or at minimum a lithium-compatible setting. The absorption/float voltages are quite different and you don't want to be pushing 14.7V into the Drift regularly. The Fogstar units are reasonably tolerant but it's worth getting right from the off.

Also worth checking your battery-to-battery charger's low-voltage disconnect threshold if you're charging from the alternator — some older B2Bs cut in at voltages that don't play nicely with LiFePO4's flatter discharge curve.

Small things, but they make the difference between the battery lasting 8 years or getting a warranty headache. How are you finding it managing without a proper lithium-compatible shunt/monitor? That flat voltage curve makes guessing SOC genuinely tricky.

Good timing on this thread — just went through the same process in my Transit last spring.

One thing worth mentioning that I don't see raised yet: check your B2B charger ratings if you're running one from the alternator. I was running a Sterling 40A unit that was fine with the AGMs but I had to double-check it was genuinely LiFePO4 compatible rather than just "compatible-ish." Some older units don't handle the flat charge profile properly and can get confused when the Drift hits absorption.

Also @VanSue — did you keep your existing battery monitor or swap it out? I found my old shunt-based monitor was giving daft readings for a few weeks until I recalibrated it properly for lithium. Once sorted it's been rock solid. The Fogstar Drift itself has been genuinely impressive for the money, I'll give it that.

Great write-up @VanSue, and welcome to the lithium side! One thing nobody's touched on yet — keep an eye on your low voltage cutoff settings if you've got any 12V appliances with built-in protection. Some older kit (compressor fridges especially) is calibrated to warn or cut out at voltages that made sense for lead-acid but will trigger far too early with LiFePO4, since lithium sits at a higher resting voltage for most of its discharge curve. Might seem like a fault when it's actually fine. Worth checking the manual or just monitoring it for the first few trips.

Great write-up @VanSue, and welcome to the lighter side of life! 😄

One thing nobody's touched on yet — keep an eye on your mains hook-up charger if you're using one on site. A lot of the older converter/chargers (especially the brick-type ones built into older motorhomes) will happily pump away at a float voltage that's just a bit too high for LiFePO4 long-term. Ideally you want something that either has a dedicated LiFePO4 profile or at least lets you set absorption and float voltages manually.

The Drift's BMS will protect it if things go properly wrong, but it's better not to rely on that as your first line of defence day-to-day.

Worth checking your charger model on here or the Fogstar Facebook group — plenty of people have already done the legwork on compatibility. Makes a big difference to longevity.

Great move @VanSue! One thing I'd add that nobody's mentioned yet — check your alternator charging setup if you're doing longer drives. The Drift's BMS can sometimes cause your alternator to see it as a short circuit when the battery's in a low state, which isn't ideal long-term. A decent DC-DC charger (B2B) like a Victron Orion Isolated sorted this for me completely. Adds a bit of cost but protects your alternator and means you're getting a proper charge profile rather than relying on the van's factory system, which really isn't designed with lithium in mind.

Really useful thread this. @VanSue one thing worth mentioning that nobody's picked up on yet — check your alternator charging setup if you're driving regularly. The Drift's BMS can sometimes confuse older split charge relays into thinking the battery's full when it isn't, because the voltage rises so quickly with LiFePO4. A proper DC-DC charger (B2B) like the Victron Orion makes a massive difference for keeping things topped up on the move. Bit of an outlay but means you're actually getting a decent charge from the alternator rather than just a trickle. Made a noticeable difference in my setup anyway.

Three people have now said "one thing nobody's mentioned yet" about alternator charging — it's been mentioned. Repeatedly.

Anyway @VanSue, my experience switching to LiFePO4 in a shepherd's hut setup (different context, I know) is that the real revelation isn't the usable capacity — it's the voltage stability under load. Your 12V appliances will actually run properly rather than browning out when the AGMs dip.

Worth double-checking your Victron or B2B charger profiles are actually set to LiFePO4 absorption/float voltages rather than AGM defaults. Easy to overlook and silently kills longevity.