Anyone else running a split charge relay alongside a B2B charger or is that overkill?

Running exactly this setup in my motorhome right now and honestly still not sure if I've overcomplicated it.

Got a Victron Orion-Tr Smart 30A B2B doing the heavy lifting from the alternator to my Fogstar 100Ah lithium. Works brilliantly — proper voltage sensing, temperature protection, all that. But I've also got an old split charge relay still wired in from the previous owner and I just... left it.

Here's where my head's at:

• The B2B is protecting the alternator properly with its current limiting
• The relay is basically doing nothing useful at that point, right?
• Or is there an argument for keeping it as a fallback?

Worried I'm either doubling up pointlessly or worse — could the two systems actually interfere with each other? I've read conflicting stuff online and half of it seems to be American setups with different alternator types anyway.

Also does anyone run a VSR (voltage sensitive relay) alongside a B2B rather than a traditional relay? Wondering if that changes things.

My setup is a 2018 Fiat Ducato base if that matters — apparently the smart alternators on these are a whole different headache which is partly why I went B2B in the first place.

Anyone else running something similar or have you just ripped the relay out entirely? What's the actual verdict?

@EcoFlowMaster similar rabbit hole here, except mine's on a narrowboat rather than a motorhome.

I ran a split charge relay alongside my Orion-Tr Smart for about six months, convinced the relay would cover those edge cases where the B2B hadn't kicked in yet. In reality, the relay was doing almost nothing useful — the Orion handles the voltage sensing and charge profiling so much more intelligently that the relay just felt like dead weight and an extra failure point.

Stripped it out entirely last spring. Simpler wiring, one less thing to interrogate when something goes wrong at a marina with no signal.

The only scenario I'd consider keeping both is if you're also charging an EV from leisure batteries on the move — timing and load management gets genuinely complicated there — but for standard aux charging, the B2B alone is the cleaner answer.

@EcoFlowMaster the Orion-Tr Smart already is your split charge relay, essentially — it's just a considerably more intelligent one that won't hammer a lithium bank with dumb bulk voltage from a Euro 6 alternator that thinks it's talking to a wet lead-acid.

Running both simultaneously is genuinely redundant unless you're using the SCR as a fallback for a completely separate battery bank. The Orion handles alternator sensing, current limiting, and charge profiling all in one box.

@CarlWalker narrowboat situation is slightly different because you're often running longer engine hours at lower RPM, so the SCR argument has marginally more merit there — but the B2B still wins on chemistry compatibility.

Honestly the only scenario I'd keep an SCR alongside a B2B is if you're paranoid about the Orion failing mid-trip with no redundancy. Which, knowing how reliable Victron kit is, feels like keeping a horse in case the car breaks down. 🐴

@EcoFlowMaster done exactly this on my narrowboat — ran both for about six months thinking the relay gave me a useful backup. What it actually gave me was a partially discharged starter battery every time the relay dumped a bit of load across at the wrong moment.

Pulled the relay out. Job done.

The Orion-Tr Smart monitors the alternator properly and won't hammer it the way a dumb relay can, especially on modern vehicles with smart alternators and variable voltage. A relay just sees "voltage is up, let's go" — it doesn't care whether the alternator is actually ready for that load.

If you're on an older van with a basic alternator, maybe there's an argument for belt-and-braces. But on anything made in the last ten years you're genuinely introducing problems, not solving them.

Not a motorhome or narrowboat bloke myself — mine's a static setup for the garden office — but I've been down this exact rabbit hole with redundancy thinking.

What I'd add: the main risk with keeping the relay active alongside the B2B isn't just inefficiency, it's that under certain conditions you can end up with unregulated alternator voltage hitting your lithium bank if the Orion drops out unexpectedly. Caught this mentioned in the Victron community forums a while back.

If you want a genuine backup, wire the relay so it only kicks in on a manual override — physically isolated during normal use. Best of both worlds without the risk.

@WezFisher curious what made you eventually drop the relay entirely — was it the above concern or just simplification?