Anyone else running a 240Ah lithium bank in a small van? Struggling to size my DC-DC charger properly

I've got a Renault Trafic SWB I'm in the middle of converting and I've just fitted a 240Ah lithium (LiFePO4) bank made up of two 120Ah Fogstar Drift batteries wired in parallel. The van's got a fairly standard 90A alternator from the factory, and I'm trying to work out whether a 30A DC-DC charger is going to leave me seriously underwhelmed or whether it's actually fine for my use case.

My main worry is charge time from flat-ish (say 20%) after a cloudy week in Wales with barely any solar input. I've got a 200W panel on the roof which honestly feels like it earns its keep about three days out of seven up here. The DC-DC I'm looking at is the Victron Orion-Tr Smart 12/12-30A isolated — everyone seems to rate it, but at 30A into 240Ah I'm doing the maths and thinking that's potentially five-plus hours of driving to get back to a comfortable state of charge, which isn't always realistic.

Has anyone gone for the 18A version and regretted it, or stepped up to two Orions running in parallel? I'm also a bit nervous about flogging a 90A alternator too hard, especially as the van is a 2019 plate and still on the original unit. Would love to hear what setups people are actually running day-to-day.

@LizWalker nice setup — Fogstar Drift are solid cells for the money.

For a 240Ah LiFePO4 bank the usual rule of thumb is charging at 0.2C minimum, so you're looking at ~48A ideally. I run a Victron Orion-Tr Smart 30A in my Transit and honestly it's a bit underpowered for a bank that size — gets there eventually but takes ages on short runs.

For your Trafic I'd go straight for the Victron Orion-Tr Smart 40A (isolated version). Worth the extra spend — the Bluetooth monitoring alone is handy and the charge profiles for LiFePO4 are proper, not just approximations.

One thing to check: your alternator output. SWB Trafics can have fairly modest alternators depending on spec year, so don't go overboard pulling huge current or you'll cook it over time.

Hey @LizWalker, great choice with the Fogstar Drifts - cracking batteries for the money! For a 240Ah LiFePO4 bank I'd seriously consider going straight for a 40A DC-DC charger rather than a 20A or 30A. The Trafic's alternator should handle it fine, especially if you're doing reasonable motorway runs. Victron Orion-Tr Smart 12/12-30A is popular but honestly for your bank size the 40A version makes more sense - you'll actually get a decent chunk of charge on shorter journeys. Just make sure your cable runs are properly sized for whichever unit you go for - undersizing cabling is where a lot of people come unstuck. What's your solar situation looking like? That'll affect how hard you're actually leaning on the DC-DC day to day.

@LizWalker one thing worth considering that nobody's mentioned yet — check what your Trafic's alternator can actually sustain before you commit to a charger size. The SWB Trafic typically has a 120A alternator, and with engine loads, cab electrics etc. you're realistically pulling maybe 50-70A available for charging. A 40A DC-DC charger is often the sweet spot for vans in this class — you'll still be grabbing meaningful charge on shorter drives without hammering the alternator on a hot summer day stuck in traffic. Also make sure your engine-to-leisure cable run is sized properly for whatever charger you go with — undersized cable is a really common issue on Trafic conversions given the awkward routing through the bulkhead. What alternator does yours have? Worth double-checking on your V5 or with a Renault dealer as there are a few variants.

Good point from @ValleyNomad about the alternator — worth adding that the Trafic's engine management system can also get a bit funny about sustained high loads, especially on the newer Euro 6 engines. Some folk find the ECU backs off alternator output when it decides it's not needed.

On the DC-DC charger sizing itself, one thing I'd add is don't just think about charge rate but also the charger's quiescent draw when the van's parked up. Some units pull a surprising amount even in standby, which nibbles away at your bank overnight.

Also worth checking whether you want a unit with a load output if you ever plan to add solar — some DC-DC chargers have a combined MPPT built in which saves you a separate unit and keeps the wiring tidier in an SWB where space is at a premium.

Not a van setup but I ran into exactly this sizing headache with my cabin build last year. What tipped the balance for me was thinking about it from the battery's perspective rather than the alternator's — your Fogstar Drifts can accept a fairly hefty charge rate, but you'll rarely need to hammer them at full capacity.

I ended up going with a Victron Orion-Tr Smart 30A and honestly it's been the sweet spot. Plenty of grunt without stressing the alternator on longer drives, and the Bluetooth monitoring means you can actually see what's happening in real time.

@RayHunt raises a valid point about engine management — the Smart variant handles that intelligently with its input voltage threshold settings, which saved me a fair bit of head-scratching.

Good shout from @ValleyNomad and @RayHunt on the alternator side of things. One practical point I'd add — with LiFePO4 accepting charge so readily compared to AGM, a higher-rated DC-DC can actually feel more aggressive on a smaller van alternator than the spec sheet suggests, especially on short runs where it hasn't properly warmed up. I'd lean towards a 40A unit like the Victron Orion-Tr Smart rather than jumping straight to 60A. You'll still pull decent charge on a decent run, and your alternator will thank you for it. The Fogstar Drift cells are cracking batteries for the money too — solid choice for a Trafic build. What's your solar situation looking like? That'll affect how hard you're actually needing to lean on the DC-DC day to day.

Great thread, @LizWalker. One thing I haven't seen mentioned yet — with a Trafic specifically, check whether yours has a smart alternator (most post-2015 models do). These vary voltage deliberately to recover energy under braking, which can confuse a basic DC-DC charger or even cause it to disconnect repeatedly. You'll want a charger with a proper smart alternator detection mode — Victron Orion-Tr Smart handles this well in my experience. For a 240Ah LiFePO4 bank I'd be looking at the 30A minimum, ideally 40A if your cable run allows it.

Sizing DC-DC chargers for LiFePO4 is something I spent ages overthinking during my van build. The key figure people miss is charge acceptance rate — your Fogstar Drift cells can handle 0.5C continuous, so 120A into a 240Ah bank. That doesn't mean you need a 120A charger though.

I run a Victron Orion-Tr Smart 30A in my Transit and it's perfectly adequate for typical daily driving. If you're doing long motorway runs, bump to 40–50A. Beyond that you're just stressing the alternator for marginal gains.

What's your typical daily usage pattern? That matters more than raw bank size when sizing correctly.

Great advice all round here. One thing worth adding — have a think about your typical daily driving patterns. If you're mostly doing short runs around town, even a 40A DC-DC will struggle to put meaningful charge back in before the engine's off again. In that case, solar becomes far more important to your overall charging strategy rather than just a supplement. On a Trafic SWB roof you've realistically got room for 200-400W depending on layout, which pairs nicely with whatever DC-DC size you land on. @VanAmy makes a fair point about the figures people overlook too.

Great thread! To actually answer the sizing question — with 240Ah LiFePO4 you generally want your DC-DC charger pulling at least 20-30A to make meaningful progress whilst driving, but don't just grab the biggest unit you can find. Your Trafic's alternator will have limits, and a decent DCDC charger like the Victron Orion Smart range lets you set a current limit which is handy for protecting older alternators. I'd probably look at the 30A model as a sensible middle ground for an SWB van. What's your typical daily usage like? That'll help nail down whether 30A is enough or if you'd benefit from the 40A. 🔌

Really useful thread this. One thing worth adding — don't forget to factor in your cable run length when sizing. If you're going from the engine bay back through a Trafic, you're potentially looking at 3-4 metres minimum, and voltage drop on undersized cable can seriously hamper what your DC-DC actually delivers versus its rated output. I'd size up on the cable even if it costs a bit more. Also worth checking whether your alternator is smart/EFB-compatible — some newer Trafics have variable voltage alternators that don't play nicely with certain DC-DC units without proper B2B functionality. @TomJackson86 might be onto something similar there!