Two mppt controllers one array

Running two Victron SmartSolar controllers off the same array on my garden office build — is this still asking for trouble, or has the master/slave setup actually sorted the old "they'll fight each other" problem?

Background: I've got a 6-panel array wired as two strings of three, and I'm genuinely torn between running one beefy MPPT (probably a 100/50) or using two smaller units I already have gathering dust from my van conversion days. The van setup was 12V, garden office is 24V, so they're not a direct drop-in, but still — free hardware is free hardware.

My understanding of why dual MPPT on a shared array was historically a nightmare:

• Both controllers independently hunting for peak power point
• They'd essentially undercut each other, neither finding true MPP
• Voltage instability across the array

But I keep reading that with Victron's networked MPPT setup via VE.Smart networking, one unit masters the sweep and the other slaves to it — meaning they're not fighting anymore, just dividing the current load cooperatively.

Has anyone actually tested this properly with a proper logging setup rather than just eyeballing the Victron app? I've got a Cerbo GX on the office system so I could pull proper data if it's worth the experiment.

Also worth noting — my array isn't shaded, dead flat site in [REDACTED because nobody needs to know where in the UK gets that little sun], so partial shading complications aren't really a factor here.

Feels like the kind of thing that's either "yeah obviously fine, mate" or "you'll regret that" and I can never tell which until I've already committed to the cable runs.

Two MPPTs on the same array without proper load sharing is just two blokes arguing over the TV remote — someone's always losing.

The VE.Smart Networking on Victron gear does help them play nicely, but you really want to split the array into dedicated strings per controller rather than paralleling them onto one lump — that's where the real trouble starts.

On the narrowboat I ran a bodged parallel setup for about six weeks before one controller basically went on holiday while the other did all the work; split the strings, never looked back.

@DuctTapeDave what's your panel layout — portrait rows or landscape blocks? Might be easier to physically separate them than you think.

@FormerMechanic43 nailed the remote analogy, but Victron's VE.Smart Networking actually gets them to agree on a programme — mine's been running two SmartSolars off the same roof on the static caravan for 18 months without a single domestic.

Has anyone actually done this on a split array rather than parallel panels? I'm trying to work out if running two SmartSolar units on separate string orientations (say east/west facing on a shepherd's hut roof) sidesteps the fighting problem entirely — each controller just tracks its own string's MPPT independently?

Or does the shared battery bank still cause issues even then?

Asking because I've got a boat setup where I'm considering adding a second Victron rather than upsizing the existing one, purely because the panels will be on different sides of the cabin roof. Feels like it should be cleaner than parallel strings, but I've been caught out before assuming solar logic matches real-world logic.

@KentCruiser does VE.Smart Networking still matter in the split-orientation scenario or is that more relevant when they're genuinely on the same string?

@BatteryPaddy yes, done exactly this on my garden office — two SmartSolars on a split array (east/west facing), works a treat actually. Each controller handles its own string independently so they're not fighting at all, they're just... doing their own thing. VE.Smart Networking still syncs the charge stages so the batteries don't get confused about what phase they're in.

That's honestly the better use case for dual MPPTs imo — different orientations mean different peak times, so you're harvesting more across the day rather than two controllers scrapping over the same curve simultaneously.

Just make sure your battery cabling is balanced between the two controller outputs or one ends up doing more work. Learned that the annoying way with my Fogstar Drift 200Ah setup.

@BatteryPaddy I've got almost exactly your setup on my static caravan — split array, south-facing roof panels on one SmartSolar 100/30 and a separate smaller string on the side elevation on another. The VE.Smart Networking genuinely does the heavy lifting; once they're both on the same Bluetooth network and you've designated one as master, they share voltage sensing and synchronise their absorption/float transitions rather than each doing their own thing independently.

The bit that tripped me up initially was battery voltage sensing — if you're relying on the controllers' own terminals rather than a proper shared voltage sense, you can get slight discrepancies creeping in. Worth wiring a dedicated sense cable to the battery if you haven't already. Made a noticeable difference on mine once I sorted it.