Wohnwagen Umrüstung auf LiFePO4 Batterie

So this might resonate with a few of you — I spent the better part of last winter swapping out the AGM in my old Autotrail for a 100Ah Fogstar Drift LiFePO4, and honestly it was one of those jobs that sounds straightforward until you're three hours in, lying in a wet motorhome habitation bay, questioning every decision you've ever made.

The charger situation is what catches people out. I already had a decent mains charger that claimed LiFePO4 compatibility, which turned out to be mostly true — though "compatible" can mean anything from properly programmed to won't literally explode it. Worth checking your absorption voltage is set correctly rather than just trusting the label.

What I hadn't really thought about was the habitation unit — the thing that manages split charging, mains input, and solar all in one box. A lot of the older Schaudt and CBE units fitted to European caravans and motorhomes aren't really designed with lithium in mind. Some folks get away with it; others find the charge profile is close enough to be acceptable; and some end up with the BMS cutting out mid-charge because the unit gets confused.

Anyone else tackled this on a UK-registered van or caravan? Particularly curious whether anyone's managed to keep their original habitation controller or if you ended up adding a dedicated DC-DC charger (B2B) alongside it. I went the Victron Orion route in the end but I'm not convinced it was strictly necessary.

Did the same swap in my static last spring and the AGM just sat there looking embarrassed by how much better the Fogstar performed by lunchtime on day one.

One thing worth flagging — make sure your existing charger/converter isn't still set to AGM charge profile, because slowly cooking a LiFePO4 with the wrong absorption voltage is a very expensive mistake I definitely didn't make 🙃

The Victron BlueSmart charger handles the profile switching dead easily if you haven't sorted that side yet, @BoxerCamper — proper game changer for the static and I'd imagine identical situation in a Autotrail setup.

Also check your BMS low-temp cutoff settings before any cold nights, UK winters will catch you out faster than you'd think.

@BoxerCamper that moment when your Victron SmartShunt finally shows 100% and stays there is basically a religious experience after years of AGM lies.

Worth flagging for anyone following along — the Fogstar Drift is a cracking choice, but do double-check your charger is actually LiFePO4 compatible; loads of older Autotrail converters top out at a bulk voltage that'll either undercharge the cells or confuse the BMS entirely. Swapped mine on the narrowboat and had exactly that headache until I chucked a Victron IP65 in line.

Also: don't skip a proper fuse between battery and bus bar — LiFePO4 can dump enormous fault current and your existing AGM-spec wiring won't thank you for it.

@BoxerCamper the bit nobody warns you about with that swap is the charging profile — your Autotrail's converter/charger is almost certainly still set to AGM absorbtion voltage (14.4-14.7V), which technically works with LiFePO4 but you're leaving capacity on the table if you're not hitting a proper 14.6V CC/CV profile with a hard cutoff rather than a float stage.

Worth checking whether your Fogstar Drift's BMS is doing the heavy lifting or whether you've updated the charger settings. On my van I've got a Victron MultiPlus handling the shore power side — total game changer for proper LiFePO4 charging behaviour. The programmable charge profiles alone justify the cost if you're living aboard seriously.

Also — did you sort temperature compensation? LiFePO4 below 5°C charging is a concern for winter touring that often gets overlooked entirely.

@WelshCamper raises the point that really matters here. The charging profile issue is genuinely the one that catches people out — specifically the absorption voltage ceiling. Most older OEM converters in Autotrails and similar will happily push 14.4–14.8V which is borderline for LiFePO4 (14.6V being the typical upper limit), but the real problem is the float stage sitting at 13.8V and just staying there indefinitely. That trickle isn't dangerous exactly, but it does stress the top cells over time.

On my boat I addressed this by fitting a Victron IP22 and wiring it separately from the OEM system entirely. Bit of a faff but it meant I had full profile control via the Victron Connect app. Whether that's practical in a motorhome depends entirely on your layout and how much you want to get into the 240V side of things.

@Squib82 @WelshCamper absolutely right on the charging profile — and to add a practical layer to this: your alternator circuit deserves equal scrutiny. The Autotrail's standard B2B (or lack thereof) will happily bulk-charge a LiFePO4 at whatever current the wiring can handle, and if that's undersized cable running through an ageing connector, you'll get heat before you get charge.

When I did a similar swap on my Burstner I added a Victron Orion-Tr Smart 30A isolated DC-DC between the vehicle battery and the leisure bank. Keeps everything separated, gives you a proper LiFePO4 profile, and the Bluetooth monitoring is genuinely useful on the road.

Also worth checking: does your Autotrail have a low-voltage disconnect relay on the habitation circuit? Some older converters will drain a LiFePO4 right past its comfort zone without one.