Anyone else had grief with a Victron Orion-Tr Smart not charging properly when the alternator voltage drops under load?

Fitted a 30A Orion-Tr Smart (non-isolated) in my Transit last month to top up a 200Ah lithium leisure battery from the starter battery. Works a treat when the engine's been running a while and voltage is sitting around 14.2V, but when I'm crawling through town — fans on, headlights, the lot — alternator voltage sags to around 13.4–13.6V and the Orion seems to just... give up. Drops to a trickle or cuts out entirely.

I've got it set to lithium profile, input lockout at 13.2V, so it shouldn't be tripping that threshold. Wiring is 10mm² cable with a 40A blade fuse close to the starter battery, runs about 1.8 metres. Connections are solid, no visible volt drop I can measure at the unit itself.

Has anyone seen this behaviour before? I'm wondering if it's a firmware thing, a configuration issue in the VictronConnect app, or just the nature of the beast with a non-isolated unit and a healthy alternator doing its job under load. I did see mention of an "engine shutdown detection" quirk in the Victron community forums but couldn't find anything definitive for my setup.

@ThistleRunner — classic Transit alternator voltage sag issue, this one. When you're pulling 30A through the Orion whilst the alternator's already under load (heating, lights, etc.), the input voltage can dip below the charger's threshold and it'll drop out or throttle back.

Worth checking your input wiring first — even a slightly underspec cable run adds resistance and makes the sag worse than it needs to be.

Also have a look in VictronConnect at your input voltage lockout settings. You can lower the "restart when above" threshold slightly to stop it cycling on and off repeatedly.

Some Transit owners run a small capacitor bank on the input side, though honestly sorting the wiring tends to fix it 90% of the time in my experience.

What year is your Transit? The newer ones with smart alternators add another layer of fun to this...

Great thread this. One thing worth trying @ThistleRunner is dropping into the Victron Connect app and having a look at your input voltage threshold settings. The Orion-Tr Smart lets you set a custom "start voltage" — if yours is set too conservatively, it'll shut off the moment the alternator sags under load rather than riding it out.

Also worth checking whether you've got the engine shutdown detection set up properly. There's a "shutdown delay" setting that can help prevent nuisance cut-offs during momentary voltage dips.

If the alternator is genuinely struggling to maintain voltage with the Orion pulling 30A on top of everything else, you might consider whether the 30A unit is actually oversized for your alternator's realistic output. Sometimes dropping input current limiting down a touch keeps things stable overall.

What engine size is your Transit? That might help narrow it down.

If your alternator's struggling to hold voltage under a 30A draw, just tell the Orion it's on a diet — drop the input current limit in VictronConnect and let the alternator catch its breath before it has a strop.

Had this exact same headache with a Sprinter build last year. Worth checking whether your Transit has smart alternator / ECU-controlled charging — many do now, and the voltage can drop to 12.8V or even lower deliberately when the engine's under load or the ECU decides it's being clever. The Orion's default input voltage threshold might be cutting out thinking the starter battery is struggling.

Have a look at your engine-running voltage with a multimeter at the leisure battery input terminals rather than relying on the van's dash readout — you might be surprised how low it actually is. If it's a smart alternator situation, an isolated version of the Orion-Tr can sometimes behave better, though @MoorRuss's suggestion of backing off the input current is a decent short-term workaround regardless.

Just to add to what @GeorgeSmith97 mentioned about smart alternators — if your Transit's post-2014ish, it's almost certainly got one. They intentionally let voltage drop to save fuel, which absolutely confuses the Orion's input threshold. Worth checking in VictronConnect whether you've got the input voltage lockout set sensibly — I had mine cutting out repeatedly because the default threshold was a touch high for what my alternator was actually delivering under load. Also make sure engine detection is configured correctly; if it's triggering off voltage alone rather than a separate ignition feed, that can cause all sorts of odd behaviour. Running a dedicated ignition wire to the remote on/off pin sorted a similar issue for me. What voltage are you actually seeing at the Orion's input terminals when it's struggling?