Anyone else running a split-charge relay alongside a DC-DC charger? Wondering if it's worth keeping both

Last summer I rewired my Transit-based van and fitted a Victron Orion-Tr Smart 12/12-30A DC-DC charger to handle the alternator-to-leisure charging properly, especially since the van has a smart alternator that makes a basic VSR pretty much useless. The Orion has been brilliant honestly — seeing a proper 14.4V absorption charge going into my 200Ah lithium rather than the 12.8V drip I was getting before.

Thing is, I never removed the old 140A split-charge relay that was already wired in when I bought the van. It's just sitting there doing nothing at the moment. I got to thinking — is there any logic in keeping it as a fallback, or even running it in parallel with the Orion for those longer motorway stints where I want to push more current into the battery quickly? Or is that just asking for trouble with the two systems fighting each other?

Current setup is a 200Ah Fogstar Drift lithium, the Orion-Tr Smart, and 200W of solar through a Victron SmartSolar 75/15. The solar does most of the heavy lifting on site but the DC-DC earns its keep on travel days. Just not sure whether the relay is dead weight at this point or whether there's a sensible use case I'm missing.

@DriftKing had the same setup for a bit — kept the old split-charge relay "just in case" after fitting the Orion-Tr Smart.

Honestly? Pulled it out after a month. Dead weight on a modern smart alternator setup. The Orion handles the voltage sensing and protects the starter battery properly — the relay was just sitting there doing nowt.

Only reason I'd keep both is if you're running a massive draw and the 30A isn't enough on its own, but even then I'd just go two Orions in parallel rather than mess about with a relay.

The relay also bypasses all that nice MPPT-style charge profiling the Orion gives your leisure bank. Bit pointless having the fancy kit and then short-circuiting it.

Chuck the relay. Trust the Victron.

Good question @DriftKing. Once you've got the Orion-Tr Smart doing its job properly, the split-charge relay is essentially redundant and can actually cause headaches. The relay doesn't care about your smart alternator's voltage behaviour — it'll just slam a connection between the banks when voltage hits its threshold, which is exactly the problem the DC-DC charger was meant to solve.

I'd remove it personally. Keeping both means you've got two different charging paths potentially fighting each other depending on conditions. Tidier wiring, less to go wrong, and the Orion handles everything the relay was doing but far more intelligently.

Only reason I'd keep a relay is if you had a specific high-current demand use case the Orion couldn't handle alone, but for leisure battery charging? The DC-DC charger wins every time.

Hey @DriftKing, I'd actually ditch the split-charge relay if your Orion-Tr Smart is set up correctly. The DC-DC charger is doing the heavy lifting and protecting your smart alternator from being hammered by a direct connection to a depleted leisure battery — which is exactly what a relay would cause. Running both simultaneously could create conflicts depending on how it's wired. The Orion-Tr Smart's engine detection via the ignition wire or voltage sensing handles everything the relay was doing, but far more intelligently. Only reason I'd keep a relay is if you wanted a basic backup for emergencies, but honestly it just adds complexity and potential fault points. Keep it clean and simple — the Victron is doing the job properly on its own. What's your current wiring setup, are you triggering the Orion via ignition live or using voltage sensing?

@DucatoBuild "essential" is doing some heavy lifting there mate — on my narrowboat I ripped the old VSR out the moment the Orion-Tr Smart was bedded in, never looked back, and the only thing it's done since is gather dust next to my emergency backup biscuit tin.

@DriftKing I went through exactly this on my Ducato build last year. The short answer for me was — ditch the relay. The Orion-Tr Smart handles the isolation between starter and leisure batteries properly, and crucially it won't try to drag your smart alternator into a sulk by demanding huge charge currents straight off the bat.

One thing worth checking though: make sure your Orion is set to the correct input voltage threshold so it only fires up once the alternator is genuinely running, not just from residual battery voltage. That catches a few people out.

Having both running simultaneously is just adding potential failure points and unnecessary complexity with no real benefit once the DC-DC charger is doing its job. Keep it tidy, trust the Victron. 😊

Jumping in to agree with @KateMitchell73 and @DonnaGibson67 here — ditched mine on my Sprinter build about 18 months ago and haven't looked back. One thing worth mentioning that nobody's touched on yet: having both active can actually cause confusion with your battery monitoring if you're running a shunt-based system like a Victron BMV. Currents coming from two different paths can muddy your readings depending on where the shunt is positioned. Keep it clean, let the Orion-Tr do its job properly, and you'll have a much tidier install with accurate data to boot. The Victron app giving you live charge status is also genuinely useful — you'd lose that visibility with a dumb relay in the mix anyway.

Echoing what others have said but worth adding one practical point nobody's mentioned yet — if you ever need to jump-start from your leisure bank in an emergency, a traditional split-charge relay gives you that option fairly easily, whereas the Orion won't help you there. Probably not a dealbreaker for most, but worth bearing in mind depending on how remote you travel. That said, @DonnaGibson67 and @DawnJones74 are right that for day-to-day charging the DC-DC charger does a far better job on its own, particularly with lithium leisure batteries where voltage-sensitive relays get confused anyway.