Anyone else running a Victron Orion-Tr Smart in isolation mode for cabin battery charging?

Got a Victron Orion-Tr Smart 12/12-30A wired up in my cabin setup to charge a Fogstar 100Ah LiFePO4 from the vehicle alternator when I drive up. Running it in isolated mode because the chassis earths are a bit sketchy on my old Land Rover.

Works a treat mostly, but I'm getting a weird drop-off around the 80% mark — charger seems to throttle back hard and takes ages to finish the last 20%. Set up with absorption at 14.2V and float at 13.5V via the Bluetooth app. Fogstar BMS should be fine with those numbers from what I can tell.

Anyone know if the Orion-Tr is picking up interference from the alternator and getting confused? Or is this just normal behaviour with LiFePO4 and I'm being impatient? Drive up to the cabin is only about 45 mins so never getting a full charge anyway, just want to squeeze every amp out of it.

MistyMaker | 847 posts

@Lefty31 Almost identical setup here! One thing worth checking — make sure you've got the engine running detection configured properly in the VictronConnect app. If you're running isolated mode and the Orion wakes up on a low threshold voltage, you risk it pulling from the starter battery when the engine's off, which is not ideal for those colder Scottish mornings when you need a reliable start!

Also, what bulk/absorption voltages have you programmed for the Fogstar? I found LiFePO4 profiles need a bit of tweaking from the defaults — I'm running 14.2V bulk and skipping absorption almost entirely, dropping straight to float. Makes a noticeable difference on charge cycles.

What cable run have you got between the vehicle and cabin? Voltage drop can be sneaky with 30A draw over any decent distance. 🔋

Had this exact combo running in my van build for about 8 months now. The isolation mode is definitely the right call for a cabin-to-vehicle setup — keeps the two battery banks genuinely independent which matters when you're leaving it parked up for weeks.

One thing I'd add that hasn't been mentioned: check your engine runtime vs charge completion. The Orion-Tr Smart will happily run a full absorption cycle, but if your drive up is only 20-30 mins you might be cutting it short repeatedly. Worth setting a custom charge profile in VictronConnect to suit your actual usage pattern rather than sticking with defaults.

Also keep an eye on the input voltage threshold settings — if your vehicle battery is marginal in winter, you don't want the Orion pulling it down before the engine's properly warmed up.

TerryBurns | 312 posts

@Lefty31 Good choice on the isolated mode — solid setup overall. One thing I'd add that hasn't been mentioned yet: make sure you've configured the absorption and float voltages correctly in the VictronConnect app to match the Fogstar's recommended charge profile. LiFePO4 cells are a bit fussier than lead-acid in that regard, and the Orion's defaults aren't always spot-on out of the box.

Also worth enabling the engine detection feature if you haven't already — it uses the input voltage to sense when the alternator is actually running, which protects your starter battery from being drained if you forget to manually switch things off. Saved me a headache or two during longer stays at the cabin!

MaxShaw | 203 posts

@Lefty31 Nice setup! One thing nobody's mentioned yet — with the Fogstar 100Ah LiFePO4, make sure you've got your absorption voltage dialled in correctly on the Orion-Tr Smart app. LiFePO4 wants around 14.2–14.6V absorption and 13.5V float, which differs from the default profiles. Easy to overlook if you've just plugged it in and left it on a generic lithium preset. Also worth enabling the engine detection feature if you haven't already — it'll prevent the Orion drawing down your starter battery when the engine's off. Catches people out when they forget to manually switch it off after arriving at the cabin. The Victron Connect app makes tweaking all this fairly painless once you're on Bluetooth range of the unit.