Anyone else noticed their Victron Orion-Tr Smart struggling to reach full charge voltage in cold weather?

Been running a 30A Victron Orion-Tr Smart DC-DC charger in my van since last autumn, feeding a 200Ah lithium (Fogstar Drift) from the alternator. Works brilliantly in summer but I've noticed over the last few weeks it's been consistently hitting around 13.8–13.9V on the output rather than the 14.2V absorption I've got set in the app. Ambient temps in the van hab section have been dropping to around 4–6°C overnight, and I'm wondering if that's playing a role somehow.

The Orion doesn't have a temperature sensor input as far as I can tell — unlike the SmartSolar units — so I can't work out if it's the charger itself derate-ing, or whether the battery BMS is pulling back the current and causing the voltage to sag. The Fogstar Drift has its own low-temp protection but supposedly that only cuts in below 0°C. I've checked my cable runs and there's no obvious voltage drop issue — 35mm² all the way, short runs, good crimps.

Has anyone seen similar behaviour and actually pinned down the cause? Curious whether it's worth sticking a small heat mat under the battery or if I'm barking up the wrong tree entirely.

Yeah, had the exact same with my shepherd's hut setup — Orion-Tr Smart feeding a Fogstar Drift 100Ah. Cold mornings it'd plateau well short of the 14.2V absorption target.

Turned out the Orion was doing its job — lithium BMS throttling acceptance in the cold. The charger looks like it's not reaching voltage but it's actually current-limited by the battery end.

Worth checking in the VictronConnect app — if you're seeing the output voltage sitting low but current is at max, that's the battery restricting, not the Orion failing.

One fix that helped me: insulating the battery compartment a bit better. Once it warms up slightly from charge cycles it accepts properly. Also double-check your input voltage threshold settings — too high and it'll drop out on shorter runs before finishing the job.

Classic case of your Orion-Tr Smart throwing a sulk because it's Baltic outside — check your temperature compensation settings in the VictronConnect app, because the default bulk/absorption voltages assume your battery isn't living in a metal fridge.

Has anyone actually looked at whether the battery temperature sensor is the missing piece here? I've been wondering if the Orion-Tr Smart is making charging decisions based on ambient temperature rather than actual cell temperature — which could be quite different if the battery is tucked away in an insulated compartment.

Also worth checking in VictronConnect — does your absorption voltage target drop in cold conditions, or is it hitting the target but just taking much longer to get there? Those are two different problems with different fixes.

Curious whether running the Orion in a warmer location (closer to the engine bay heat) versus the battery being cold makes the issue worse or better for anyone?

@DaleBen good shout raising this — I've seen similar behaviour with mine over winter. One thing worth checking that nobody's mentioned yet is whether your Orion-Tr Smart is actually seeing the correct input voltage from the alternator in the cold. On colder mornings some alternators take a while to reach full output, so the Orion may be throttling back simply due to marginal input headroom rather than anything temperature-related on the battery side.

Worth logging the input voltage via the VictronConnect app during a cold morning drive to rule that out first before diving into sensor territory. Also double-check your cable sizing — voltage drop becomes more significant when currents are lower and connections are slightly corroded from winter damp.

Good shout from @RogerJackson — the battery temp sensor is exactly what I'd look at first. The Orion-Tr Smart does support the Smart Battery Sense via Bluetooth networking, and if you haven't paired one up, the charger is essentially flying blind on actual battery temperature. Worth noting too that lithium cells genuinely need a lower charge current when cold — below about 5°C you really don't want to be pushing full current into them anyway, so the Orion backing off isn't entirely a bug. If your Fogstar has a built-in BMS with low-temp cutoff, it might actually be throttling things from that end rather than the Orion itself. Have you checked the BMS data in the Fogstar app to see whether it's reporting any temperature faults? That'd help narrow down whether the issue is charger-side or battery-side before you go down the rabbit hole.