Anyone else finding the Victron Orion-Tr Smart a bit oversized for a small van build?

Just finished wiring up my Transit Custom camper conversion and I went with the Victron Orion-Tr Smart 12/12-30A isolated unit, mainly because everyone on here seems to rave about it. It works an absolute treat, don't get me wrong, but at 360W input it feels like massive overkill for my 100Ah lithium leisure battery. On a decent run down the motorway I'm barely scratching the surface of what it can do.

I'm running a 200W solar setup on the roof as my primary charging source, so the DC-DC is really just a backup for those grey winter days when we're out for a weekend and the sun's nowhere to be seen. Realistically I'm probably only needing to top up 20-30Ah on most trips. Makes me wonder if a 12/12-18A unit would have been the smarter (and cheaper!) choice.

Has anyone gone with one of the smaller Orions, or even a competing unit like the Sterling B2B, and found it perfectly sufficient for a modest setup like mine? I paid around £180 for mine — curious whether I've genuinely overspent or if the headroom is actually useful down the line. Would love to hear what others are running.

@Jess1972 the 30A unit does feel like overkill on a smaller build, agree. That said, I ran a 18A non-isolated unit in my Transporter for a while and genuinely wished I'd sized up — charge times from the alternator were noticeably longer on back-to-back driving days.

Worth considering: the Orion-Tr Smart throttles itself back anyway based on alternator load detection, so you're not always pulling full rated current. With a smart alternator (which the Transit Custom almost certainly has), it'll be doing its soft-start dance regardless.

If your leisure battery is sub-100Ah, the 18A isolated version would've been sufficient. Above that, the 30A earns its keep fairly quickly. Fogstar and other budget DC-DC options exist but the Victron's Bluetooth monitoring and absorption/float logic genuinely justify the premium on a permanent install in my experience.

@Jess1972 worth remembering the 30A pulls around 360W from your alternator — on a Transit Custom that's probably fine, but on a smaller engine it can cause issues at idle. I ran the 12/12-18A isolated in my Berlingo for two years without complaint. Charges my 100Ah Fogstar Drift lithium quickly enough on a decent run.

The 30A unit does make more sense if you're planning to upsize your battery bank later though. Easier to right-size the charger now than rewire everything in 12 months when you inevitably want more capacity. Personal experience talking there 😅

One thing nobody mentions — the Bluetooth monitoring via the Victron Connect app is genuinely useful regardless of which size you go for. Being able to see exactly what's happening during charging while driving is worth it alone.

@Jess1972 Worth noting that "oversized" isn't necessarily a problem with DC-DC chargers the way it might be with inverters — the Orion-Tr Smart will throttle output based on input voltage, so it won't hammer your alternator unnecessarily. That said, if your lithium bank is modest (sub-100Ah), the 18A isolated unit would've done the job and saved you £40-50.

Where the 30A genuinely earns its keep is if you're ever adding EV trickle-top-up capability or expanding your battery capacity later — I've got a similar isolated unit in my cabin setup feeding a 200Ah Fogstar Drift bank and it barely breaks a sweat on long runs. The Bluetooth monitoring via VictronConnect is arguably the best justification for either size anyway. What's your alternator rated at? That's often the real limiting factor people overlook.

@Jess1972 ran the exact same unit in my Berlingo conversion before I moved to a bigger build. Felt massive for the space, but here's the thing — that 30A is derated by temperature, so on a warm summer run it's rarely pulling its full rated output anyway. What actually sold me on keeping it was the Bluetooth monitoring. Sat in a lay-by on the A303, watched it respond intelligently to the alternator load in real time. That's the bit the cheaper units can't touch. If you're genuinely space-constrained, Victron do the Orion-Tr Smart 18A — smaller footprint, still isolated, still has the app. But honestly, once it's tucked behind a panel you'll forget about the size entirely.

@Jess1972 my garden office doesn't even move and I still ended up with the 30A — turns out "overkill" is just another word for "won't have to upgrade it in six months" 😄

@NickBennett ha, "overkill is just another word for confidence" — should be stitched on a cushion in every van builder's cab.

The thing nobody tells you with the 30A is that it throttles itself anyway based on alternator load and battery state. So in practice you're rarely seeing the full 30A pulled. My Berlingo setup spent most of its life cruising at 15-18A whilst the Victron quietly got on with it. The sizing anxiety kind of dissolves once you watch it in action via the app.

Where it genuinely earns its keep is on longer motorway runs — that's when you actually want the headroom to fill a decent lithium bank (I was running 100Ah Fogstar cells) before you pull off for the night. A 12A unit would've left me short more than once.

@Jess1972 I had the same initial feeling with mine in a Promaster City build — looks enormous sat there next to everything else! But honestly after one winter of driving shorter distances and still arriving at camp with a decent charge, I stopped worrying about the size. The thing is, with lithium you really want that higher charge rate when your driving time is limited. A 30A unit earning its keep on a 40-minute motorway run is far more useful than a "perfectly sized" 18A that leaves you scrambling for a hookup. You'll appreciate it come January, trust me!

Ran a 12/12-18A non-isolated in my setup for ages before upgrading. Honestly? The 30A earns its keep faster than you'd expect once you're running bigger loads off the leisure bank.

The size thing is just Victron being Victron — built like a tank, lasts forever. Mine's been baking in a poorly ventilated spot for two summers without complaint.

Only caveat: make sure your alternator can handle sustained draw. Newer Transits with smart alternators can be funny about it — worth double-checking the Orion's charge profile settings match what your vehicle expects.

@Jess1972 The physical size threw me off too when I first installed mine in a Sprinter. Worth remembering that a decent chunk of that bulk is the thermal management — Victron's built the heatsinking right into the casing rather than relying on a separate fan. In a confined van environment that's actually a genuine advantage, especially in summer. Also, with the Smart variant you've got the Bluetooth monitoring which you'll wonder how you managed without once you're actually on the road checking charge states from your phone. Give it a season and I suspect the size will stop bothering you entirely.