Victron Orion-Tr Smart 30A vs 18A for cabin leisure bank — worth the extra cost?

Finally getting round to sorting proper DC-DC charging between my van's starter battery and the 200Ah Fogstar Drift LiFePO4 leisure bank in the cabin. Running a 12V system throughout. The alternator is a standard 110A unit on a 2019 Transit, so not one of the smart/variable voltage Euro 6 types that causes all the drama — just a straightforward setup.

I've been looking at the Victron Orion-Tr Smart isolated units. The 12/12-18A (220W) is sitting around £130, while the 12/12-30A (360W) is closer to £200. On paper the 30A makes sense — faster charging when the engine's running — but I'm genuinely not sure if the Transit's alternator will tolerate the extra load, especially with the cab heating, headlights, and stereo all drawing at the same time. Has anyone actually measured alternator temp or seen belt slip issues running the 30A unit continuously?

The cabin use case is fairly modest: 12V compressor fridge (~4A average), a few USB/12V outlets, and LED lighting. The 200Ah Fogstar shouldn't need massive charge currents to stay healthy, and the Victron's absorption/float profile handles the LiFePO4 chemistry well enough with a custom charge profile. But I do occasionally run the van for 2–3 hours specifically to top the bank up after a cloudy week with poor solar input from the 400W rooftop array.

Main question is whether the real-world gain in charge speed justifies £70 extra, or whether the 18A is genuinely sufficient for this kind of intermittent use. Anyone running either unit on a similar Transit/LiFePO4 combo with actual numbers?

Lefty25 | 847 posts

@CrispyMender for a 200Ah LiFePO4 I'd lean towards the 30A personally. The maths works out nicely — you're looking at roughly a 0.15C charge rate which LiFePO4 handles brilliantly, and you'll actually put meaningful amps in during shorter drives rather than barely tickling the bank.

The price difference is maybe £40-50 depending where you shop, and spread over the life of the unit it's nowt really.

One thing worth checking first — what alternator are you running? Some of the older or smaller units on vans don't appreciate being hammered by a DC-DC constantly pulling 30A. If it's a decent modern alternator you'll be absolutely fine, but worth knowing before committing.

Both units are cracking bits of kit either way. The Smart integration with Victron Connect makes setup dead straightforward too.

Bazza60 | 1,203 posts

@CrispyMender one thing worth factoring in that gets overlooked — the Orion-Tr Smart 30A pulls roughly 35-36A from the starter side to deliver 30A output due to conversion losses. Worth checking your alternator rating and wiring gauge can handle that sustained draw, especially on longer cable runs where voltage drop compounds the issue.

I run the 18A into a 100Ah Fogstar and it suits my use case fine — leisure bank topped up within a reasonable drive. But with 200Ah LiFePO4 you've got more headroom to exploit, and the 30A will recover that bank meaningfully faster after overnight loads.

Also check whether your alternator has smart charging/variable voltage management — some newer vehicles need the engine running detection configured carefully in VictronConnect to avoid false triggers.

MistyTinker | 2,156 posts

@CrispyMender something nobody's mentioned yet — thermal derating. The 30A unit will throttle back in a warm engine bay or cab installation far more aggressively than you'd expect, sometimes dropping to 18–22A sustained anyway. I've seen this firsthand running an Orion-Tr Smart 30A in my motorhome; summer driving it rarely hits full output unless I've got decent airflow around it.

Also worth checking your alternator's actual continuous rating rather than the peak figure. Older or smaller alternators can struggle with a constant 30A draw on top of vehicle loads — the 18A is genuinely kinder there.

If your install location has decent ventilation and your alternator is 100A+, the 30A earns its price premium. Otherwise the 18A is no compromise at all for a 200Ah bank given typical drive durations.

DerekKnight | 412 posts

Good shout from @MistyTinker on thermal derating — worth keeping in mind depending on where you're mounting it.

One angle I'd add: consider your typical driving patterns. If you're doing mostly short runs — nipping to the shops, site hookups under an hour — the 30A's higher charge rate means you're actually putting meaningful amps back in during limited engine time. With the 18A you might barely be scratching the surface before you're parked up again.

The Fogstar Drift handles 1C charging comfortably, so the 30A isn't going to stress it. The price difference between the two units is roughly £50-60 last I looked — spread over years of use that's fairly negligible. I'd spend the extra personally.

WingAndPrayer | 634 posts

@CrispyMender one angle I'd add — cable run length between your starter battery and the leisure bank matters here. If you've got more than a couple of metres, voltage drop on the input side can cause the 30A unit to throttle back anyway, so you'd want decent 6mm² or even 10mm² cable to get the rated output reliably.

I've got the 18A version between my tow vehicle and a shepherd's hut setup, and for a 200Ah bank it honestly keeps up fine with realistic daily discharge cycles. The 30A is lovely but unless you're doing serious daily mileage to replenish heavy overnight draws, the 18A payback period versus the price difference takes a while. What's your typical drive time between uses?

UC_Builds | 1,847 posts

@CrispyMender to add something fresh to the thread — consider your actual use pattern. If you're regularly doing short drives (under 45 minutes), the 30A unit will recover meaningful charge in limited engine runtime, whereas the 18A might leave you perpetually playing catch-up, especially through winter with higher loads.

That said, the 30A draws more from your alternator simultaneously, so if you've got any concerns about alternator health or age, that's worth factoring in.

The Bluetooth monitoring on both units is genuinely useful for dialling in the settings with LiFePO4 — make sure you configure it properly for the Fogstar Drift's charge parameters rather than leaving it on default. Fogstar publish recommended settings on their site which takes the guesswork out.