Victron Orion XS 12/12-50A charing cycles every second instead of charging continuously

Had something similar crop up with my static caravan setup last summer — worth sharing in case others have seen this.

Running a Victron Orion XS 12/12-50A feeding a 200Ah Fogstar Drift lithium bank from the tow vehicle alternator. Everything fires up fine initially, pulls a solid 45-48A as expected, then within a minute or two it starts cycling — dropping out and reconnecting every second or so. Looks almost like a protection fault but no alarms showing in VictronConnect.

A few things I've narrowed it down to:

• Alternator voltage sag — smaller euro-spec alternators can't sustain output under heavy load, causing input voltage to dip below the Orion's threshold repeatedly
• BMS communication — if your lithium BMS is talking to the Orion via the H/L port, any hesitation from the BMS can trigger this cycling behaviour
• Cable sizing — I was initially underspec'd on my input side; voltage drop was pushing me right on the edge

In my case it turned out to be a combination of thin input cabling and the BMS briefly flagging high charge current before settling. Re-crimped with proper 35mm² cable and added a small delay setting in VictronConnect — sorted it.

Anyone else seen this with the XS specifically? I know the older Orion-Tr Smart had similar quirks but the XS seems more sensitive to input conditions. Curious whether this is more common with certain alternator types — particularly the smart/variable voltage ones on newer vehicles.

Would be interested to know if anyone's resolved it differently, especially if you're running a shepherd's hut or caravan off a tow vehicle long-term.

@OldSparky18 saw almost exactly this with my shepherd's hut build last spring. Turned out the issue was the Orion dropping into protection because it was reading a false voltage spike on the input line — loose crimp on the starter battery positive was causing momentary drops that the unit interpreted as "charge complete, disconnect, reconnect."

Worth checking a few things before diving deeper:

• Cable terminations both ends, not just the obvious ones
• Engine running vs. static — does it cycle when the donor battery is under load?
• VE.Direct logs if you've got it connected to a Cerbo or laptop; the fault history is surprisingly detailed on the XS

The Orion XS is genuinely fussier about input quality than the older TR models. Fogstar Drifts are well-behaved BMS-wise in my experience, so I'd look upstream first.

Proper thread this — good stuff getting documented here 👍

@OldSparky18 welcome to the forum by the way, great first post! Nothing like jumping straight in with a meaty technical issue rather than just lurking 😄

One thing worth checking that hasn't been mentioned yet — have a look at your engine detection voltage threshold in the Orion XS settings via VictronConnect. If it's set too high, the unit can keep thinking the alternator's dropped out and reset the charge cycle repeatedly. Caught me out on the boat before I realised what was happening.

Also worth double-checking your input cable crimps — a slightly dodgy connection can cause just enough voltage wobble to confuse it. Learned that one the hard way on my garden office build!

Shepherd's hut here too @SolarNeil so this thread is very relevant to me 👀

Worth checking your cable run length as well — I had a similar cycling issue and it was down to voltage drop across an undersized cable making the Orion think the source was dropping below its threshold. Bumped up to 16mm² and it sorted itself right out.

Also double-check the engine detection threshold setting in the VictronConnect app if you're running it off a vehicle — sometimes it's set too sensitive and it's basically playing on/off with itself trying to confirm a valid source.

Both fixable without spending a penny, which is always nice 😄

Good shout on the cable run @GazAllen — though I'd also look at the connection quality at both ends before assuming it's length alone.

On my narrowboat I had cycling behaviour that turned out to be marginal crimps on the input side causing momentary voltage dips. Orion XS is quite sensitive to input voltage — if it drops below threshold even briefly it'll reset the charge cycle.

Worth checking:

• Crimp quality on both positive and negative runs
• Input fuse/breaker rating — undersized protection can cause nuisance trips under load
• Whether the remote on/off wire has a stable signal

If you've got a Victron MPPT or Cerbo in the system, the VRM portal history can show exactly when the cycling starts and correlate it with battery voltage — much easier than guessing.