Anyone else running a Victron MPPT alongside cheap Chinese panels — what's your actual real-world yield?

Picked up four 200W "Renogy-style" panels off eBay back in spring — no-name brand, £60 each, delivered. Wired them as two strings of 2S in parallel into a Victron SmartSolar 100/30. On paper that's 800W of potential, but I've never seen more than about 480W peak on the Victron app, even on a clear July day here in Yorkshire. Panels are tilted at roughly 35° facing south, so I don't think the angle is the issue.

I know UK irradiance isn't exactly the Sahara, but 60% of rated output on a decent summer day feels low. Victron's absorption and float figures look sensible — sitting at 14.4V and 13.8V — and the controller itself seems to be doing its job. Makes me wonder if the panels are just wildly overrated from the factory, or whether there's something else going on.

Has anyone done a proper comparison between budget panels and something like Longi or JA Solar on the same controller? Curious whether spending the extra on decent panels actually shifts the numbers meaningfully, or if the Victron is just pulling the best out of whatever you throw at it regardless.

@JackHunt interesting setup — I'm running something similar on the narrowboat, four 175W no-names (Alibaba direct, even sketchier than yours) into a SmartSolar 150/35.

Honest yield figures: panels are consistently 10-15% under their claimed wattage at peak. Doesn't bother me massively because the Victron side of things is rock solid — the MPPT algorithm genuinely wrings out every electron those panels will give.

Worth checking your actual Voc before trusting the label. Mine were spec'd at 45V open-circuit, measured 42.8V on a cold clear morning. Not catastrophic but worth knowing, especially if you're calculating string voltage headroom.

The VRM portal data is where the truth lives — have you logged a full sunny week yet? I'd be curious what your panel temp looks like mid-afternoon because that's where cheap cells really start dropping off.

@JackHunt that combo sounds almost identical to what I ran for 18 months on my Transit conversion before I upgraded.

Honest answer? The yield was surprisingly decent — not far off what my Victron app predicted on clear days. Where it fell apart was on heavy overcast; those no-name panels dropped off a cliff compared to the half-decent Renogy branded ones I added later.

The SmartSolar really earns its money here though. MPPT tracking is doing a lot of heavy lifting when the VOC from dodgy panels wanders about with temperature.

One thing worth checking — measure your actual panel VOC individually with a multimeter. Two of my four were noticeably mismatched, which tanks your string performance something rotten. Swapped the worst offender and saw a genuine 10-15% improvement overnight.

What's your battery bank sitting at? That affects the numbers significantly too.

Hey @JackHunt — cracking little setup that. I've got three 250W panels from a similarly dubious eBay listing running into a SmartSolar 150/35, and honestly the yield has surprised me. On a decent July day here in the Hebrides I'm pulling 85-90% of the theoretical max, which given the panel quality I wasn't expecting. The Victron's MPPT algorithm seems to squeeze out every last drop regardless of what you throw at it.

Worth checking your VRM data for clipping events though — I noticed mine were occasionally hitting the controller's current ceiling around midday in summer. Might be worth logging a few days and seeing if you're leaving anything on the table. @OffGridTel curious what your narrowboat figures look like across seasons, given you've presumably got more shading variables to contend with on the cut.

Been running a similar mishmash for three years now — cabin gets four 200W panels of mysterious Chinese heritage wired into a Victron SmartSolar 150/35, and the motorhome runs two 175W panels through a 100/20.

Honest answer: the yield gap between these and branded panels is smaller than you'd expect. Where the Victron earns its money is in proper MPPT tracking when panels are partially shaded or thermally derated — cheap controllers throw yield away during exactly those conditions.

One thing worth checking @JackHunt: pull your VRM data and look at the absorption phase duration. If it's suspiciously short, your panels' actual Voc is likely lower than the spec sheet claims. Mine were about 8% down. Factor that in and suddenly the yield makes perfect sense — panels underperform, Victron extracts what's actually there. That's the real pairing benefit.

Running almost exactly this on the shepherd's hut — four 175W panels of deeply questionable provenance feeding a SmartSolar 100/20. The Victron's MPPT algorithm genuinely rescues mediocre panels from themselves; I've watched it squeeze yield out of overcast November afternoons that a PWM controller would've completely squandered.

What I have noticed is the rated wattage on cheap panels tends to be optimistic by around 10–15%. My Victron history logs told the honest story pretty quickly — peak harvest sits noticeably below what the spec sheets promise.

That said, the combination works brilliantly. Let the dodgy panels be dodgy; the Victron compensates. Three seasons in and nothing's failed yet.

@JackHunt — worth pulling your yield data from the VictronConnect app and benchmarking against your location's peak sun hours. PVWatts will give you a realistic baseline to compare against.