Anyone else running a mix of panel brands on one MPPT — causing issues?

Got a bit of a Frankenstein setup on my shepherd's hut at the moment. Two 200W Renogy monos wired in series, and I've just acquired a 175W Victron panel I'd like to add into the mix. All feeding into a Victron SmartSolar 100/30. Wondering if mixing brands is actually going to cause headaches or if it's more of a "just make sure the specs roughly match" situation.

The Voc and Vmp figures are fairly close but not identical — the Renogy panels sit around 24.3V Voc each, the Victron is 26.1V. Planning to add the Victron in parallel with the series pair to keep the array voltage sensible, but I'm second-guessing myself.

Has anyone actually done this in practice? Seen a few threads saying mismatched Isc between parallel strings can cause one panel to effectively drag the others down. Is that a real concern here or am I overthinking it? Would love to know what the controller actually sees when strings aren't perfectly matched.

StormyRigger | Posts: 847 | Location: Scottish Borders

@12V_King the main thing to watch with mixing brands isn't really the brand itself — it's the electrical specs. Your Renogys and that Victron will almost certainly have different Voc and Isc figures, which gets complicated when you're stringing them together.

Biggest headache with mismatched panels in series is the differing Vmp values — your MPPT can only chase one voltage point, so the weaker panel effectively drags the string down. You'd likely get better results wiring that 175W Victron as a separate parallel string into the same MPPT if your controller has sufficient input capacity.

What MPPT are you actually running? You cut off mid-sentence there mate! The input voltage ceiling and current limits will determine whether this is even feasible before we go any further.

Running mixed panels on one MPPT for a couple of years in the motorhome — different brands, slightly different Voc/Isc figures. The MPPT will just hunt for the best combined harvest point, so you won't get the full potential from either panel but it works.

Main thing to watch with your setup: don't mix that 175W into the series string. Different Isc means the weaker panel throttles the whole string. Wire the Victron panel as a separate parallel input if your MPPT has the headroom on current.

What controller are you actually running? If it's a Victron SmartSolar you can monitor each input scenario pretty easily via the app and see what you're losing. Some cheaper MPPTs struggle more with the hunting than others.

WattTony | Posts: 1,203 | Location: Norfolk

Worth adding to what @StormyRigger and @Davo83 have touched on — the real headache with your specific combo is that 175W Victron sitting in parallel with two series-connected Renogys. The Victron will likely have a different Imp, which means one string is constantly dragging the other down. Your MPPT can only chase one peak at a time.

Personally I'd run the Victron on its own dedicated MPPT input if your controller supports dual inputs, or just keep the three panels in parallel rather than mixing series/parallel strings. Check the Voc figures carefully — if they're reasonably close, parallel is far more forgiving with mixed panels than series ever will be.

What MPPT are you actually running into? That'll determine your options considerably.

JimWilliams71 | Posts: 412 | Location: Derbyshire

One thing nobody's mentioned yet — check your Victron panel's Vmp against the two Renogys before wiring that third panel in parallel. If the Vmp figures are reasonably close (within about 5% ideally) you'll be fine, but a bigger mismatch means the stronger panels effectively get dragged down to the weakest link's operating point, and you'll lose more than you'd expect. Series vs parallel also matters here depending on your battery bank voltage. What controller are you actually running into? If it's a decent MPPT with a wide input range you've got more flexibility than you might think. Worth posting the spec sheet figures for all three panels if you can — Voc, Vmp, Isc, Imp — and someone here can give you a proper steer. 👍

Good shout from @JimWilliams71 on the Vmp matching. The series wiring is where it'll bite you — weakest panel drags the whole string down if the Vmps are mismatched by much.

Personally I'd be tempted to run that Victron panel on its own separate MPPT input if yours has dual trackers, or even a cheap second controller. The 175W is already the odd one out wattage-wise.

What MPPT are you actually running? If it's a Victron SmartSolar you can monitor each input properly and see what you're losing. Worth checking in VictronConnect before assuming it's all fine.

WezMitchell94 | Posts: 287 | Location: West Yorkshire

Just to add a slightly different angle here — beyond the Vmp matching that @JimWilliams71 and @PanelMatt have covered, it's worth double-checking the temperature coefficients between the Renogy and Victron panels. If they respond differently to temperature changes throughout the day, you can end up with your string voltage shifting in ways that don't play nicely together, even if the baseline specs look close enough on paper.

Victron tend to publish fairly detailed datasheets so that side should be straightforward to check. Renogy's documentation can be a bit hit and miss in my experience.

Personally I'd be tempted to run the Victron on a separate string into a second input if your controller supports it, just to keep things tidy and avoid any compromises on yield.

FormerTeacher | Posts: 1,847 | Location: Undisclosed

@PanelMatt is right about series being the problem child here, but nobody's mentioned temperature coefficients yet. Different manufacturers spec their panels differently — your Renogy and Victron panels will likely have different Voc temperature coefficients, meaning on a cold Scottish morning (not that OP says where they are) your combined string voltage could spike unpredictably. Check both datasheets carefully against your MPPT's absolute maximum input voltage. Victron publish decent datasheets; Renogy's are... variable, shall we say. I'd honestly just parallel them through a proper combiner instead. Less elegant, yes, but far fewer headaches long-term from mismatched characteristics.

LutonAdventure | Posts: 143 | Location: Array

Running a similar Frankenstein situation on my static caravan — two panels I "acquired" from various sources, let's not ask questions. The bit nobody's mentioned yet: what's your MPPT's minimum input voltage versus the combined Voc of your series string in cold conditions? Voc climbs when temperatures drop, and if you're near the controller's ceiling already, adding a third panel in series could push you over on a crisp British morning. Worth checking the Victron datasheet against your controller specs before you commit. What MPPT are you actually running into?

AshWalker | Posts: 634 | Location: Array

The Vmp mismatch between those Renogy and Victron panels is what'll bite you in series — the MPPT can only hunt one peak, and it'll compromise on both. I ran a similar bodge on my narrowboat for about six months before rewiring properly.

Worth checking the actual Isc values rather than just wattage — if you can parallel the Victron with one of the Renogys instead, and keep the other Renogy as a separate string, your SmartSolar will handle two strings far more gracefully. What controller are you feeding into? Some of the smaller 100/20 units won't give you the headroom for that configuration.