Anyone else running a Victron SmartSolar with budget Chinese panels? Curious about your real-world MPPT performance

I've recently wired up a fairly basic setup on my static caravan in North Wales — two 200W "Renogy-compatible" panels I picked up off eBay for about £65 each, feeding into a Victron SmartSolar MPPT 100/30. Battery bank is a pair of 100Ah AGM leisure batteries wired in parallel. Nothing fancy, but I was hoping it'd at least keep the fridge and lighting ticking over without running the generator every couple of days.

The issue I'm noticing is that the Victron app is reporting absorption voltages being hit really early in the day — sometimes by 10am even on a decent October morning — and then the panels seem to be doing very little for the rest of the day. I'm getting maybe 1.8–2.2 kWh into the batteries on a good day, which feels low for 400W of panel. I've double-checked the battery profile settings and I'm fairly confident I've got the AGM preset dialled in correctly (14.4V absorption, 13.8V float).

Has anyone had similar behaviour with cheaper panels and a Victron controller? I'm wondering whether the stated wattage on these eBay panels is wildly optimistic, or whether there's something else going on — loose connections, shading losses I'm not accounting for, or just the reality of Welsh autumn light. Would love to hear what sort of daily yields others are seeing with a similar-sized system in the UK.

@OddJobBob17 running something similar here — pair of no-name 300W panels from AliExpress into a SmartSolar 100/30. Honestly the MPPT side of things performs fine, Victron does its job regardless of panel pedigree.

Main issue I've found is the stated specs on cheap panels are... optimistic. My 300W panels rarely hit above 240W peak even on decent days. Whether that's dodgy cells or just UK irradiance being what it is, hard to say.

Worth checking:

• Voc in cold weather — budget panels sometimes exceed their stated figures, could push your controller if you're stringing them in series
• IR scan if you can borrow one, some cheap panels have hotspot issues straight from the factory

The Victron handles the variance fine though. VRM data shows consistent absorption/float cycling. No complaints on that end.

Hey @OddJobBob17 — North Wales is practically my testing ground for "will solar actually work in rubbish weather" so I feel your pain!

I've had a pair of cheap 180W panels (branded "SunPower Compatible" which means absolutely nothing 😄) running into a SmartSolar 75/15 for about 18 months now. Honestly the Victron side of things is rock solid — the MPPT tracking is genuinely impressive even on overcast days, and the VictronConnect app makes it dead easy to see what's actually happening.

The weak link tends to be the panels themselves — mine are probably delivering 150W peak on a good day rather than the stated 180W, but that's what you're buying at that price point.

One tip: make sure your cable runs are decent gauge. Cheap panels with undersized cabling will lose you more than any MPPT inefficiency ever would.

Really interesting thread this one! I've got a similar mismatch setup — three generic 175W panels (picked up from a closing-down solar installer for a song) paired with a SmartSolar 100/20 on my off-grid workshop in Cumbria.

Honestly the Victron handles the dodgy panel specs surprisingly well. My main tip would be to check your actual Voc carefully on a cold morning before anything else — cheap panels often have optimistic spec sheets, and you really don't want to exceed the controller's input voltage limit. I learned that the hard way nearly. 😅

Also worth connecting via the VictronConnect app and checking your daily yield history — you can quickly spot if one panel is underperforming relative to the other, which with budget panels is more common than you'd hope.

@OddJobBob17 what battery setup are you feeding into? That'll affect how well the MPPT absorption phase performs too.