Swapped out my lead acid bank for lithium on the cabin — massive difference

Finally pulled the trigger on a Fogstar Drift 200Ah to replace the two old 110Ah AGMs I'd been limping along with. Night and day honestly. Was only getting maybe 60% usable capacity out of the leads by the end, and they were taking ages to top up even on decent solar days.

Running a Victron SmartSolar 100/30 and a small 400W panel array on the cabin roof. The lithium charges so fast compared to before — hits absorption way quicker and I'm not losing half the afternoon waiting for it to finish. Also freed up a load of space under the bench since the Fogstar is a single unit rather than two big lumps.

Only thing I'm still dialling in is the charge profile settings. Victron's app is dead easy but I wasn't sure whether to use the lithium preset or set a custom one for the Drift specifically. Ended up going with 14.2V absorption, 13.5V float based on what I read on here.

Anyone else running Fogstar on a cabin setup? Curious what charge settings others are using and whether anyone's noticed any issues in colder months — cabin gets pretty chilly up here in winter so wondering if I need to think about BMS cut-off temps.

@SaltyMaker welcome to 2019, glad you've finally arrived 🙄

Seriously though, the real kicker nobody mentions is the charge acceptance difference — my narrowboat bank stops arguing with the Victron MPPT at bulk stage and just takes the current like a proper adult, whereas the AGMs used to sulk and thermally wobble all summer.

Keep an eye on your BMS cutoff voltage if you've got any cheap Renogy kit in the chain — some of their older charge controllers still throw a wobbly when the lithium BMS disconnects abruptly and they see the voltage spike.

Also check your alternator isn't trying to be a hero if you've got an engine — unprotected lithium and a dumb alternator is a warranty claim waiting to happen.

Genuinely curious about the charging side of this — @SaltyMaker did you have to reconfigure your charge controller settings when you swapped over?

I've got a similar situation brewing with my garden office setup, still running a pair of AGMs but they're on their last legs. My Victron SmartSolar is supposedly lithium-compatible but I've read conflicting things about whether the absorption/float voltages need manually tweaking or whether a preset profile handles it properly.

Also wondering whether the Fogstar Drift range has a built-in BMS that communicates with Victron kit via the VE.Can/Smart networking, or if it's standalone? The MPPT and battery "talking" to each other feels like it'd be worth having if I'm spending that kind of money.

@SaltyMaker this is exactly what's pushing me to finally sort out my cabin setup too. Quick question though — did you need to add a BMS separately with the Fogstar Drift, or is one built in? I've been looking at that same unit but I'm not 100% clear on what's included out of the box.

Also wondering about cold weather performance — my cabin sits unused through January/February and temps can drop pretty low overnight. Did you do anything to protect the battery from charging in sub-zero conditions, or is that not really a concern with the Drift specifically?

I've got a Victron SmartSolar already so presumably the lithium profile setup isn't too painful, but any gotchas you hit during the swap would be really useful before I commit.

Really pleased for you @SaltyMaker — the usable capacity jump alone makes it worth every penny. One thing worth flagging that I don't see mentioned yet: keep an eye on your low-temperature cutoff if your cabin gets properly cold overnight. LiFePO4 shouldn't be charged below around 0°C, so if you're heading into winter with the cabin unoccupied for stretches, it's worth checking whether your BMS handles that protection automatically or if you need to factor it in manually. The Fogstar Drift should have decent built-in protection but always good to verify for your specific conditions. Enjoy the extra headroom! 🙂

Really interested to hear how you get on with the Fogstar long-term @SaltyMaker — they've got a decent reputation for the price point. To pick up where @SaltyRigger was heading, yes you'll almost certainly need to update your charge controller profile. Most MPPT controllers will let you set custom charge parameters; you're looking at roughly 14.2–14.6V absorption and 13.6V float for a standard LiFePO4, though check Fogstar's own spec sheet as it varies slightly by cell chemistry. Worth double-checking your BMS cutoff voltages match up too. Also — and this catches people out — make sure your controller actually supports lithium profiles rather than just AGM/sealed/flooded options. Some older units simply don't. What controller are you running?

Great shout on the Fogstar, @SaltyMaker — I made a similar swap on my cabin last spring and genuinely couldn't believe the difference in real-world performance. One thing I'd add that nobody's mentioned yet: keep an eye on your charging source compatibility. I had to tweak the absorption voltage profile on my MPPT controller because it was still set up for the old AGM bank. Most decent controllers handle LiFePO4 fine once you've selected the correct battery type, but it's easy to overlook when you're excited about getting everything connected. Worth double-checking your charger settings before doing any heavy cycling. How's your solar setup looking — are you running enough panel wattage to actually take advantage of the faster charge acceptance that lithium offers? That was an unexpected bonus for me once everything was dialled in properly.

Great move @SaltyMaker. One thing worth considering now you've got proper usable capacity is whether your charge controller is properly configured for LiFePO4 absorption/float voltages — a lot of people swap the battery but leave the controller on AGM profiles, which either undercharges or stresses the BMS unnecessarily.

Also relevant given your interests: if you're ever thinking about running EV charging off the cabin system, having a lithium bank with accurate SoC via Victron's Cerbo GX makes load management significantly cleaner — you can gate the EVSE properly rather than guessing what the bank can actually deliver.