Orion 12 12 17 charging concern

Been mulling this one over since I noticed something similar on the boat last week.

Running a Victron Smart Lithium 200Ah with the Smart BMS CL 12-100 and an Orion-Tr Smart 12/12-18 for alternator charging alongside a 100/30 MPPT. What I've been wondering is whether the Orion and the MPPT are playing nicely together when both kick in during that final charging stage.

Specifically — when the battery is sitting at say 95-100% SOC, the Orion seems reluctant to taper off properly even when the MPPT is already pushing absorption current. The BMS hasn't triggered any alarms, but I'm not fully confident both chargers are genuinely talking to each other rather than just doing their own thing independently.

On a narrowboat you're often running the engine and getting decent solar simultaneously in summer, so this isn't a rare edge case for me — it happens pretty regularly on sunny cruising days.

A few questions I'd throw out there:

• Has anyone actually verified via VRM or Bluetooth that the Orion correctly backs off when another charger is handling the tail end?
• Does the BMS NG version handle this coordination differently to the older CL-series BMS?
• Anyone found a specific Orion charge profile tweak that helps here?

Not panicking — the system is broadly working — but lithium doesn't forgive sloppiness at the top end the way AGM does, so I'd rather understand what's actually happening before it becomes a problem.

Curious whether anyone else has dug into this properly.

@BerlingoLife interesting one — are you seeing this on the Victron Connect app or just noticing it from behaviour?

I had something similar when I set up DC-DC charging between my tow vehicle and the static caravan setup. Worth checking whether your Smart BMS CL 12-100 is actually sending the correct remote on/off signal to the Orion. Mine was intermittently dropping the load disconnect line which caused all sorts of odd charging behaviour.

Also — is your Orion set to standalone mode or engine detection? If it's engine detection, are you certain the voltage threshold is being met consistently? Sometimes a slightly tired starter battery won't trigger it reliably.

What firmware versions are you running on both the BMS and the Orion? There were some known quirks that got ironed out in later releases.

@BerlingoLife the Orion-Tr Smart 12/12-18 (you'll see it listed as 17A in some firmware versions, same unit) has a known quirk where it'll throttle output current when the alternator voltage droops below roughly 13.2V — worth checking your alternator's actual output under load rather than assuming it's healthy.

On my motorhome I had a similar issue; turned out the B2B was behaving perfectly correctly but my aging alternator was sagging badly once the Orion drew sustained current. Fitted a Sterling Power alternator protection relay as a precaution.

Also worth checking: is the Smart BMS CL 12-100 LOAD output feeding the Orion's remote H-line? If that connection is intermittent, you'll get exactly the erratic charging behaviour you're describing. Check the crimps on that remote terminal — mine had a loose pin causing identical symptoms.

@BerlingoLife the BMS CL 12-100's LOAD output isn't rated to drive the Orion's remote H-pin directly in all conditions — stick a small relay in between or you'll end up wondering why your Orion keeps throwing a strop at inconvenient moments, usually somewhere on the M6.

Also worth checking: the Orion-Tr Smart needs its engine detection threshold set correctly in VictronConnect, otherwise it'll happily try to charge off a starter battery that's already on its knees — seen blokes on here blame the BMS when it's actually just pulling from a 11.9V starter under load.

@RustyRoamer is right about the 17/18A naming — same hardware, different firmware labelling, ignore it.

@FormerCop that H-pin gotcha has bitten more people than a Vauxhall Vivaro with dodgy wiring — stick a proper relay in between and sleep soundly.