Orion XS only 120 watts

Been scratching my head over something similar with my static caravan setup and wondered if anyone else has hit this wall.

I've got an Orion XS 50A (12/12 non-isolated) pulling from a leisure battery bank to top up a Fogstar Drift 200Ah LiFePO4, and I'm only seeing around 120W output rather than the ~600W I'd expect at 50A.

A few things I've already ruled out:

• Cable sizing (running 16mm² throughout)
• BMS cutoff (checked, all looks fine)
• Victron Connect settings — nothing obviously capped

My suspicion is that the input voltage is sagging under load, so the XS throttles back to protect itself. Has anyone measured their alternator or source battery voltage while the Orion is actually running? I'm wondering if I need a bigger input-side battery buffer before the charger.

Also curious whether the absorption/bulk thresholds in the app need tweaking for LiFePO4 chemistry specifically — the defaults feel like they might be holding things back.

Is this a known limitation when the source battery isn't beefy enough, or am I missing something obvious in the config? Would be good to hear from anyone running a similar setup on a boat or van where the input source is variable.

Hey @RussWebb, looks like your post got cut off there mate! You were saying about pulling from a leisure battery - what's on the other end, and what voltage are you actually seeing at the unit when it's running?

My first thought with Orion XS units throttling back is usually voltage drop on the input side. That 50A draw needs proper cable sizing - people often underestimate it. What gauge are you running and how long's the cable run?

Also worth checking - have you configured it through VictronConnect? The input current limit and the voltage thresholds can catch people out if they're still on defaults. Sometimes the unit's protecting itself because it's seeing the input voltage sag under load.

Give us the full picture and I'm sure we can get to the bottom of it! 🔧

@RussWebb looks like we lost the rest of your post - @Nobby30 beat me to pointing that out!

That said, "Orion XS 50A only doing 120W" is a pretty classic symptom I've seen discussed a fair bit, so I'll have a stab in the dark while you finish the thought.

120W at 12V is exactly 10A - suspiciously round number. Usually means one of three things:

1. BMS current limiting on either the source or destination battery
2. Voltage sag on the source dragging the XS into a derated operating range
3. Engine-running detection misconfigured (if you're feeding from a vehicle-side battery)

For static caravan use specifically, what's your source battery chemistry? If it's a tired AGM pulling down under load, the XS will throttle itself rather than drag the voltage below its input threshold.

Finish your post and we'll get to the bottom of it properly!

@RussWebb post got cut off but I suspect I know where this is going — the Orion XS will throttle back significantly if the input voltage drops. At 50A draw the source battery needs to be sitting comfortably above 12.5V under load or it'll derate to protect itself.

Worth checking what voltage you're actually seeing at the input terminals of the unit during operation, not just at the battery posts. Cable gauge and run length matter enormously here — I was seeing nearly 0.4V drop on a 2m run with undersized cable on my garden office setup before I sorted it.

Also confirm your VE.Direct config — there's a minimum input voltage threshold in the settings that defaults conservatively. Victron's Connect app will show you exactly what the unit thinks it's receiving.

What's your cable cross-section and approximate run length from leisure battery to Orion?

@CarlBaker is almost certainly right — mine did exactly this on the narrowboat until I sorted the cable run; Victron's own docs basically say "give it fat cables or it'll sulk like a teenager."

@EssexNomad raises something worth dwelling on — cable resistance is the silent killer here, and people consistently underestimate it.

On my narrowboat I ran 70mm² cable for my Orion XS specifically because the run from the bow battery bank to the stern was nearly 6 metres one way. Even a fraction of an ohm of resistance in that circuit will cause the Orion to see a falsely depressed input voltage and throttle accordingly.

Worth checking with a proper multimeter: measure voltage directly at the Orion's input terminals under load, not at the battery posts. If there's more than 0.3V drop across that run, you've found your culprit.

@RussWebb — your post did cut off, so we're partly guessing, but if your cable gauge and run length don't match up, that's almost certainly the story here.