Anyone else running a Victron Orion-Tr Smart in non-isolated mode? Getting odd behaviour at low SOC

I've had a Victron Orion-Tr Smart 12/12-30 running between my van starter battery and a 100Ah lithium leisure battery for about six months now. Generally brilliant piece of kit, but I've noticed something a bit odd lately. When the leisure battery drops below around 20% SOC, the Orion seems to cut out and then restart repeatedly — short cycles of maybe 30–40 seconds on, then off. It's not throwing any fault codes in the VictronConnect app, just showing "bulk" briefly before dropping back to standby.

I've got it wired non-isolated, which I know some people have strong feelings about. Cable run is roughly 1.5m each way using 10mm² cable, so voltage drop shouldn't be the issue. The alternator on the van is a standard 90A unit and the engine is running when this happens, so it's not a case of the starter battery being pulled down.

I've had a poke around the settings and I'm wondering if the "engine detection" voltage threshold is set too high and it's falsely thinking the engine has stopped. Currently set at 13.2V which is the default, but maybe the alternator voltage is dipping slightly under load and tripping it? Has anyone played with that setting and found a sweet spot, or is there something else I'm missing here?

@Curly7 what voltage threshold have you set for the input low voltage shutdown? I had similar weirdness on mine in the garden office setup — turned out my shutdown voltage was set too close to the resting voltage of the starter battery, so the Orion was cutting in and out repeatedly as the alternator tried to compensate.

Also worth checking — are you running the latest firmware? There was a patch a while back that addressed some instability in the absorption phase when input voltage was marginal.

What's your engine running voltage actually measuring at the Orion input terminals under load? Sometimes there's enough voltage drop in the cabling to cause grief even when the alternator output looks fine at the battery.

Hey @Curly7, worth checking whether you've got the ignition input wired up properly. If the Orion's relying solely on voltage sensing to detect engine-on state rather than a dedicated ignition signal, you can get odd behaviour at low SOC where the leisure battery's absorption demand pulls the starter voltage down enough to confuse it. It'll sometimes cycle on and off hunting for a stable input.

Also, are you running the latest firmware? There were a few fixes around low-voltage behaviour in recent releases — connect it up through VictronConnect and check. What @Nobby's saying about the input threshold is definitely worth investigating alongside this though, the two issues can compound each other. What does your VictronConnect history tab show — are you seeing repeated connect/disconnect events logged?

Good shout from @Cerbo_Guy on the ignition wire — I'll add something slightly different though. On my shepherd's hut build I ran the Orion-Tr Smart in non-isolated mode between a split-charge setup, and the behaviour you're describing often comes down to adaptive algorithm confusion when the input voltage is borderline.

Worth diving into VictronConnect and checking your engine shutdown detection settings. If that's set too aggressively, the Orion starts second-guessing itself when the alternator voltage dips momentarily under load — particularly on older vehicles where voltage isn't rock-steady.

Also, are you running any other loads directly off the starter battery? Even a small parasitic draw can confuse the voltage-based detection at marginal SOC. Log a session in VictronConnect and watch the input voltage graph — the pattern usually tells the story immediately.

Good points already from @Nobby and @Cerbo_Guy on the thresholds and ignition wiring.

One thing not yet mentioned: in non-isolated mode, check your common negative routing carefully. If your chassis ground path has any meaningful resistance — corroded body earth, undersized cable — the Orion sees a slightly elevated voltage at the input terminal compared to actual battery voltage. At low SOC this discrepancy matters; the unit may think the starter battery is healthier than it is, delaying shutdown, or conversely triggering protection erratically depending on where you've taken your sense reference.

I had exactly this on a backup system I built using a Victron Orion 12/12-18 — swapping to a dedicated negative cable directly back to the starter battery negative post rather than relying on chassis ground sorted it entirely.

Worth pulling the VictronConnect logs too — the history tab will show exactly what triggered any protection events.

Non-isolated mode on a lithium leisure bank is basically asking the Orion to have an existential crisis — your starter battery's resting voltage and the leisure bank's resting voltage are close enough that the unit occasionally can't decide who's charging whom. 🔄

Worth jumping into the VictronConnect app and checking your input voltage lockout is set above your leisure battery's resting voltage at the SOC where things go wobbly — otherwise you get that lovely bidirectional confusion at around 12.8V where both sides look identical to the Orion.

Fogstar Drift cells are particularly guilty of this because their voltage curve is so flat — been there in my own van build, nearly convinced myself the unit was faulty before realising I'd basically built a philosophical paradox into my wiring diagram.