Anyone else finding the Victron Orion-Tr Smart 30A keeps dropping into absorption early on a cold morning?

Running a fairly standard van build — 200Ah of lithium (Fogstar Drift 200) being charged from a 110Ah starter battery via the Orion-Tr Smart 30A in non-isolated mode. Works brilliantly in summer but now we're into the colder months I'm noticing it regularly jumps into absorption after only 10–15 minutes, even when the leisure battery is sitting at 30–40% SoC. Outside temps around 4–6°C at the time.

I've got the Victron Connect app open and the input voltage looks fine — sitting at 14.1–14.2V from the alternator once it's warmed up. The leisure battery itself reads 13.1V going in, so it's not like it's already full. My gut says it might be the battery temp sensor reading cold cells and the unit backing off, but I haven't got a dedicated temp sensor wired to the Orion — just relying on the BMS cutoffs in the Fogstar.

Has anyone else seen this with lithium and the Orion-Tr Smart specifically in winter? I'm wondering whether adding the Victron battery temperature sensor (the little plug-in one) would actually help here, or whether this is more likely a charge profile setting issue. Currently on the default lithium preset — absorption at 14.2V, float at 13.5V.

BitsAndBobs9 | Posts: 847

@LochSeeker yes, seen this exact thing! Worth checking whether your Fogstar has its own BMS temperature cutback happening — the Drift series can throttle accepted current quite aggressively when cold, which the Orion interprets as the battery being "nearly full" and bumps it into absorption prematurely.

Have you got the Orion connected via VE.Direct or Bluetooth to VictronConnect? If so, check the charge current graph — if it's dropping sharply rather than tapering naturally, that's almost certainly the BMS pushing back rather than anything wrong with the Orion itself.

Parking somewhere slightly warmer overnight, or a small self-heating pad under the battery, sorted it for me during last winter. Bit of a faff but it works.

Brummie92 | Posts: 312

@LochSeeker yeah this caught me out last winter with a similar setup. The thing people often miss is that the Orion-Tr Smart is reading its own internal temperature, not the battery's. On a cold morning the unit itself might be sat somewhere draughty near the bulkhead, so it's throttling back and jumping to absorption prematurely based on that rather than what the battery actually needs.

Worth having a look at where the Orion is physically mounted — if it's near any cold air ingress that'll make it worse. I moved mine closer to the battery bank and the behaviour improved noticeably. Also double-check your bulk voltage threshold in the VictronConnect app isn't set too conservatively for lithium. Small tweak but it made a difference for me.

JessPhillips | Posts: 1,203

@LochSeeker worth having a look at your absorption voltage threshold in the Victron Connect app. On cold mornings lithium internal resistance shoots up, so the Orion sees voltage spike faster than expected and thinks it's time to step down — even though the battery isn't actually full.

Try dropping your absorption voltage trigger slightly, or if you haven't already, enable the temperature compensation settings. Also worth checking whether your cable runs are adequate — any extra resistance in the circuit will compound the problem in the cold.

What temperature are we talking roughly? Below about 5°C it becomes noticeably worse in my experience. If the Fogstar BMS is also throttling charge acceptance in the cold that'll make things even more pronounced. Two separate systems both reacting to temperature can cause a bit of a perfect storm.

RogerKnight | Posts: 203

One thing worth investigating that I haven't seen mentioned yet — have you verified the cable cross-section and run length between your alternator and the Orion input? Undersized cabling causes a voltage drop that the Orion interprets as the input source being under stress, which can trigger early state transitions.

On my narrowboat I had a similar peculiarity with a 30A unit until I moved from 10mm² to 16mm² on a fairly modest 2-metre run. Night and day difference in behaviour.

Also worth asking: what's your input lockout voltage set to in the VictronConnect app? If it's configured even slightly high, cold-morning voltage sag on the starter battery could be causing the Orion to briefly cut and re-enter the charge cycle partway through — which might look like premature absorption but is actually something else entirely.

What does the history tab in VictronConnect actually show?

Trigger63 | Posts: 847

@LochSeeker something worth checking that nobody's touched on yet — what's your cable run length between the alternator/starter battery and the Orion? Long runs with even slightly undersized cable can mean meaningful voltage drop, and on a cold morning when the alternator is still warming up and output voltage is on the lower side anyway, the Orion can see a reduced input voltage and interpret conditions differently than expected. Worth measuring actual input voltage at the Orion terminals rather than at the battery itself. Even a 0.3-0.4V drop can nudge things. Also, have you got engine detect set up properly? If it's triggering off a marginal voltage reading on a cold start rather than a clean signal, that can cause odd behaviour in the charge profile from the off.

OffGridAlan | Posts: 2,156

@LochSeeker classic cold weather headache this one. Something nobody's mentioned yet — the Fogstar Drift BMS itself can be the culprit here. In cold conditions the BMS occasionally throttles incoming current, which causes the Orion to see reduced acceptance and misinterpret it as the battery approaching full. The unit then bumps into absorption prematurely even though your actual SOC is still low.

Worth checking whether the Drift has any low-temperature charging protection kicking in — Fogstar's spec sheet should confirm the threshold. If you're regularly parked somewhere exposed overnight, even a simple insulating wrap around the battery can make a noticeable difference before you start tweaking Victron settings.

Also, what firmware are you running on the Orion? There were some absorption threshold improvements in recent versions worth having.

SaltyViking | Posts: 412

@LochSeeker worth checking your Orion's input voltage threshold settings in the VictronConnect app. In cold weather your alternator can take longer to get up to full output, and if the Orion sees the starter battery voltage dip even briefly below your configured input lockout voltage, it'll reset the charge cycle and jump straight to absorption when it reconnects. Try nudging your input voltage lockout down a touch and see if that stabilises things. Also, what's your charge profile set to? Fogstar Drift cells are fairly tolerant but incorrect absorption voltage can make the whole thing look odd on cold mornings.