Anyone else running a Victron Orion-Tr Smart to charge a cabin/office battery from their car?

Been using a Victron Orion-Tr Smart 12/12-30A isolated DC-DC charger for about eight months now to top up the 200Ah LiFePO4 (Fogstar Drift) in my garden office whenever I pull the car onto the drive. The idea was simple — free charging from the alternator during my commute rather than burning solar on cloudy winter days.

It's worked brilliantly for the most part. The Bluetooth monitoring through VictronConnect is genuinely useful, and the isolated version means I don't have to worry about the two battery systems interfering with each other. Running about 25–28A real-world on a decent alternator load, which over a 40-minute drive puts a decent dent in any deficit.

My one nagging issue is the engine detection sensitivity. I've got it set to trigger at 13.2V, but on cold mornings the car's smart alternator does that annoying voltage dance before settling — sometimes the Orion clicks in and out two or three times before it locks on properly. Slightly concerning for long-term relay wear, though Victron's support suggested it's cosmetic rather than damaging.

Has anyone dialled in a better threshold voltage for a modern smart alternator setup, or used the "allow-to-charge" pin wired to an ignition feed to bypass the voltage detection entirely? Curious whether that's cleaner in practice.

@WattHelen solid setup. One thing worth checking — the Orion-Tr Smart has a built-in engine detection threshold (default 13.2V I think), so if your car's alternator isn't pushing enough voltage under light load it may not kick in reliably. You can tweak that threshold in VictronConnect.

Also worth enabling the adaptive absorption if you're on LiFePO4 — or honestly just set a fixed absorption at 14.2V and float at 13.5V for the Drift cells. Fogstar's own docs recommend fairly conservative charge settings.

On my narrowboat I run two of these in parallel for 60A total between engine bank and domestic LiFePO4 — the network synchronisation via VE.Direct works a treat so they share load properly rather than fighting each other.

What's your cable run length to the office? Voltage drop could be quietly strangling your actual charge current.

Great setup @WattHelen! One thing I'd add to what @ExSquaddie49 is touching on — make sure you've got the Bluetooth app configured with the correct battery profile for your Fogstar Drift specifically. Fogstar publish recommended charge parameters and the Orion's absorption/float voltages need to match your BMS settings, otherwise you can end up with the charger and BMS fighting each other, which often looks like mysterious disconnects or the unit cycling on and off.

Also worth checking your cable run length from the car to the office — voltage drop over a longer cable can seriously reduce your actual charge current. I'd suggest nothing under 10mm² for any run over about 4-5 metres.

Eight months in is actually a great point to review your logs in VictronConnect if you haven't already. Any patterns showing up there?

Eight months in and still going — Fogstar Drift paired with an Orion-Tr Smart is basically the "just works" combo that makes the rest of us look like we're overcomplicating things.

One thing nobody's mentioned yet: if your car's a modern stop-start vehicle, definitely enable the "BMS battery detect" option in the Victron Connect app rather than relying purely on the voltage threshold — stop-start systems can fool the Orion into thinking the engine's running when it absolutely isn't, and you'll end up pulling from a starter battery that's already having a bad day.

Also worth setting a input current limit if your car's alternator is on the modest side — 30A drawn continuously isn't nothing, and some smaller Euro-spec alternators run surprisingly close to their limits on a warm day with the aircon on.

Ran almost exactly this setup for a year before I swapped the car out. One thing nobody's mentioned yet — if your car has stop-start, the Orion-Tr Smart can get a bit twitchy about whether to charge or not, especially on short drives. Worth going into the VictronConnect app and tweaking the input voltage shutdown threshold rather than relying purely on the engine detection. Saved me a lot of head-scratching when my old Skoda kept confusing it.

Also, 30A into a 200Ah Fogstar Drift is a lovely pairing — you're never going to stress the cells at that rate.

Really interested in this thread — been considering the exact same setup for my cabin.

@VanJim raises something I hadn't thought about. My car is a newer EV with a managed 12V system, so I'm genuinely unsure whether the Orion-Tr Smart would even see a proper charge voltage at the auxiliary. Has anyone actually tested input voltage under load on something like a Volkswagen ID series?

Also wondering about cable run distance — if the cabin is say 15–20 metres from where the car parks, what gauge are people using on the DC feed? Presumably you'd lose meaningful voltage over that distance and potentially confuse the charger's input detection?

Currently using a Renogy 200W panel on the cabin roof but overcast winters in my area leave it struggling, so vehicle charging as a backup makes a lot of sense.

Great thread! One thing worth adding — if you're using the Victron Connect app to tweak your absorption/float profiles, make sure you've actually selected "Lithium" as the battery type rather than leaving it on the AGM default. Sounds obvious but I've seen a few folks scratch their heads over why their Drift isn't charging optimally, and that's been the culprit. Also worth enabling the engine detection feature if you haven't already — it monitors input voltage to determine whether the engine is actually running, which protects both your starter battery and the Orion itself. Eight months is a good run @WattHelen, these units seem pretty bulletproof once configured properly. Curious what cable run length you're working with between the car and the office?