Can I run two DC-DC chargers in parallel?

Been wrestling with this for a few weeks now, so thought I'd ask the collective wisdom here.

Currently running a single Victron Orion-Tr 48/24-16A to top up my auxiliary battery bank from the alternator while the van's running. Works brilliantly when I'm stationary, but I've noticed the charge current drops significantly when I'm actually driving—probably because the alternator can't sustain the load alongside other vehicle systems.

Here's the thing: I've got access to another identical charger, and I'm wondering if I can wire them in parallel to split the load. In theory it sounds sensible—two 16A chargers sharing the input current would mean less strain on the alternator and potentially faster charging overall.

But I've got nagging doubts. Are there synchronisation issues? Do I need specific firmware or communication between the two units? Would they fight over voltage regulation and cause instability?

My setup is fairly straightforward—48V Fogstar LiFePO₄ bank, 200A BMS, standard split-charge relay from the starter battery. The alternator's a decent unit on a newer engine, so it should theoretically handle it.

Before I go down the rabbit hole of wiring this up, I'd rather hear from someone who's actually done it (or tried and regretted it). Are there any gotchas I'm missing?

Cheers for any insight.

Running two DC-DC chargers in parallel isn't straightforward, mate. The Victron Orion units don't play well together that way—you'll likely get voltage regulation conflicts and one will end up doing all the work while the other sits idle or even feeds current backwards.

What's your actual power requirement? If you're maxing out a single 16A unit, you'd be better off stepping up to the Victron Orion-Tr 48/24-25A instead. Cleaner solution, single control point, and you avoid the parallel headaches.

If you really need splitting loads between chargers, look into master/slave configurations with compatible units—but honestly, that's overkill for most van setups. What's driving the need for two chargers rather than one larger unit?

The issue @JoeTurner's hinting at is current sharing. Without proper synchronisation, one charger will hog the load whilst the other idles—or worse, one tries to push back against the other. You'd need them on different battery banks entirely to avoid this mess.

If you're after more charging capacity, honestly, stepping up to a single larger unit makes more sense. A 48/24-24A would give you genuine headroom without the complexity. I've got two separate DC-DC circuits in my setup (one for leisure, one for emergency), but they feed completely isolated battery systems.

What's your actual charging requirement? If you're looking at expansion, knowing your amp-hour target and average charge time would help point you toward a proper solution rather than working around hardware limitations.

The real issue is voltage regulation. Both chargers will try to regulate to their programmed voltage setpoint, and whichever reaches it first will drop its output current while the other compensates. You end up with unpredictable load sharing and potential oscillation.

If you genuinely need more charging capacity, I'd say swap for a single larger unit — a Victron Orion-Tr 48/24-32A would be more stable and reliable. Works out cheaper too in most cases.

Only time I'd consider parallel is if you've got a proper battery management system with droop current sharing enabled on both units, and frankly that's more complexity than most of us need for an auxiliary bank. What's your actual charging requirement? Might be there's a simpler solution depending on your van/setup.

Looking at this from an emergency backup angle — have you considered whether you actually need two chargers running simultaneously, or are you after redundancy if one fails?

If it's pure capacity you're after, the voltage regulation conflict @LiFePO4Fan mentioned is the killer. Both units will fight for control and you'll end up with unpredictable behaviour, potentially damaging your auxiliary bank.

What might work better:

Diode isolation — fit a high-current blocking diode on each charger's output so they don't "see" each other. You lose a bit of voltage drop (typically 0.7V per diode) but they won't interfere. Victron actually makes diode modules for this.

Sequential switching — use a relay to switch between chargers based on alternator voltage. One active at a time means proper voltage regulation.

Single larger unit — honestly, a 48/24-24A or 48/24-32A might be simpler than juggling two smaller ones. What's your actual charge current requirement?

What's driving the desire for two units? If it's backup redundancy for off-

Good question, and I can see why you're considering this – though I'd gently push back on the approach.

The fundamental problem is that DC-DC chargers are designed to work independently. Without hardware synchronisation (which most consumer units don't have), you'll get fighting between the two units as they try to regulate voltage independently. One will end up doing most of the heavy lifting whilst the other barely contributes, defeating the purpose entirely.

If you genuinely need higher charging current, your best bet is upgrading to a single larger charger – something like a Victron 48/24-20A would give you that headroom without the complications. Alternatively, if this is about redundancy for reliability, fair enough, but they'd need to be on separate battery banks.

What's driving the need for dual chargers? Is it purely about charging speed, or are you after backup capacity? That'll help clarify whether there's a cleaner solution.

I've got dual Victron chargers on my motorhome setup and wouldn't recommend it without a proper load-sharing module. They'll fight over voltage regulation and you'll get inefficient charging at best, potential damage at worst. If you need more grunt, step up to a single larger unit instead — cheaper and more reliable.