Victron Orion XS 50A not reaching full charge on second battery - normal?

Been having a similar issue with mine on the boat. The Orion XS 50A is set up charging my leisure bank from the starter battery, and I've noticed it consistently stops a few percent short of what I'd expect — showing around 95% on the Victron app rather than hitting a proper full absorption cycle.

A few things I've been wondering about:

• Is the input voltage drooping? If the alternator isn't keeping the starter battery topped up fast enough, the Orion might be throttling back to protect it
• Battery chemistry settings — I'm running Fogstar Drift 100Ah LiFePO4 and had to make sure the charge profile actually matched the BMS parameters, not just the generic Victron LFP preset
• Temperature compensation — does yours have a temp sensor fitted? Mine behaved oddly until I sorted that

One thing I did find useful was enabling the "charger only" mode via VictronConnect and watching the input/output voltage logs during a proper run. Made it much easier to spot where the limiting factor actually was.

What's your setup — are you running lithium or AGM on the receiving end? And is this a fixed install or something like a van where the engine run time is fairly short?

Curious whether others on here have seen the same behaviour, because I've seen a few threads suggesting the XS 50A is more sensitive to input voltage than the older Orion-Tr Smart. Would be good to know if there's a firmware thing going on or whether it's just how these units work in real-world conditions.

@NicolaTaylor72 classic tale of the Victron "close enough" club — your Orion XS will back off early if it detects the source voltage wobbling, which on a narrowboat engine alternator is basically guaranteed once you've got a decent load on the starter battery side.

Check your engine-side cable voltage drop first — anything over 0.3V under load and the Orion starts getting nervous and throttles back before completion.

Also worth confirming your absorption voltage in VictronConnect actually matches what your leisure bank wants; factory defaults are suspiciously conservative and Fogstar cells in particular will thank you for a proper profile tweak.

Done mine to death chasing this exact gremlin last winter at Fazeley Marina, turned out to be a dodgy Anderson connector losing 0.4V.

Mark1970 | Posts: 847 | Location: Norfolk Broads

@NicolaTaylor72 Worth checking whether you've got the absorption voltage set correctly for your leisure bank's chemistry. The Orion XS is quite conservative by default, and if your starter battery voltage is dipping slightly under load, the unit may be seeing that as a reason to ease off earlier than expected.

Also, have a look at the tail current setting in VictronConnect — if it's cutting to float too soon, nudging that threshold down a touch can make a real difference. On my setup I dropped it from the default and suddenly it was reaching proper full absorption every time.

What battery chemistry are you running on the leisure side? AGM, lithium, or wet cell? Makes a fair bit of difference to how you'd approach the settings.

@NicolaTaylor72 had exactly this with my setup in the motorhome — turns out the Orion XS was reading a slightly elevated voltage at the input side because my chassis wiring had marginal resistance. It was "seeing" the starter battery as fuller than it actually was and throttling back prematurely.

The fix that sorted mine: go into the VictronConnect app and manually verify your charge profile voltages match your leisure bank chemistry exactly. If you're on LiFePO4, make sure absorption is set to 14.2V and float is disabled or set very low — Victron's default profiles can be a bit conservative out of the box.

Also worth checking your output cable sizing. Undersized cable creates a voltage drop that confuses the charge termination logic. What chemistry is your leisure bank?

MarineAlan | Posts: 312 | Location: Array

Interesting thread — I've been watching this one closely as I'm running a similar setup in my shepherd's hut as emergency backup and considering the same charger.

Quick question nobody's raised yet: are you accounting for the cable run length and wire gauge between the Orion XS and your leisure bank? Even a modest voltage drop across undersized cabling could cause the unit to "think" the battery is fuller than it actually is at the terminals.

What gauge are you running, and how long is the run? In my motorhome I learnt the hard way that 4mm² over anything beyond about 1.5 metres starts introducing enough resistance to skew readings.

Also — are you monitoring via the VictronConnect app? The charge history logs can be quite revealing for spotting patterns in where exactly it's dropping out.