Anyone else running a budget 12V system off cheap Chinese panels? Sharing my numbers

I've been piecing together a van setup on the cheap over the last six months and wanted to share what I've actually found vs what I expected. Running two 200W "200W" panels off eBay (Eco-Worthy branded), wired in parallel into a Victron 75/15 MPPT. The panels rarely hit anything close to 200W — on a decent summer day here in Yorkshire I'm seeing maybe 260-270W peak combined, so call it 65-67% of rated output. Not shocking given the price, but worth knowing going in.

Battery side I've got a pair of 100Ah LiFePO4 cells from Fogstar (the Drift ones, 12V, proper BMS built in). Those I'd actually recommend without hesitation — solid bit of kit for the money and they've held their rated capacity through about 40 cycles so far. Total spend to get the core system running was roughly £480 including the MPPT, panels, cabling, and a cheap 40A DC-DC charger from the alternator.

The part I'm still unsure about is whether I'd have been better off spending a bit more on two decent 175W panels from a reputable brand rather than the dodgy eBay ones. The Eco-Worthy panels do the job but I don't trust the longevity, and one of them already has a small delamination bubble near the junction box after one winter.

Has anyone done a direct comparison between budget panels and mid-range stuff like Bimble or Photonic Universe over a proper length of time? Curious whether the efficiency gap closes or widens as they age.

@DefenderConvert the Eco-Worthy panel tolerance issue is well documented — most of those 200W units are pushing 170-180W peak under ideal conditions, and that's before you factor in UK irradiance which is nothing like the STC figures they're tested at.

I ran similar panels on my shepherd's hut build before I got fed up and switched to proper Risen modules. The difference was measurable — not massive, but real.

Actual thing worth checking: grab a cheap DC clamp meter and measure your string current at solar noon on a clear day. Compare against the Isc spec. That'll tell you exactly how badly you're being robbed.

Also worth noting — the "200W" rating is under 1000W/m² irradiance. In the UK you're realistically averaging 800-900W/m² on a good summer day. Adjust expectations accordingly rather than blaming the controller.

@DefenderConvert similar story on my narrowboat — I've got a couple of budget panels bolted to the roof and the real-world output told a very different tale to the sticker.

What changed everything for me was adding a Victron SmartShunt so I could actually see what was coming in rather than guessing. Turns out I was making decisions based on optimistic numbers for months.

The panels themselves aren't necessarily the whole problem either — shading from chimneys, aerial mounts, whatever's on your roof adds up fast on a boat. I'd wager a decent chunk of your missing watts is disappearing there before you even factor in the panel tolerance @SolarJunkie mentioned.

What MPPT controller are you running? That'll tell you a lot about where the losses are sitting.

@DefenderConvert running a very similar story on the narrowboat. What nobody mentions with cheap panels is the degradation curve — my Renogy budget units were already off-spec after eighteen months of canal life (constant vibration, temperature swings, occasional low branch encounters...).

The number that actually saved me was measuring string voltage at noon on a clear day versus the spec sheet. Anything more than 8% down and you know something's dodgy before you've even looked at output watts.

Ended up pairing my sketchy panels with a proper Victron MPPT and the difference in extraction efficiency honestly softened the blow of underperforming panels. The controller earns its money when the panel itself is already lying to you.

Worth logging daily yield in a spreadsheet for a few weeks — patterns tell you more than any single reading.

@DefenderConvert been running a similar cobbled-together setup on my boat for a couple of years now. The panel wattage thing is real but honestly what caught me out more was the dodgy MC4 connectors that came with the cheap panels — had one arc a bit which was fun 😬

Worth spending a fiver on decent replacement connectors rather than trusting the ones bundled in.

Also if you're not already — pair those panels with even a basic Victron MPPT rather than the PWM controller they usually throw in the box. Made a noticeable difference to what I was actually pulling into my Fogstar cells. The controller that came with my Renogy kit was genuinely terrible by comparison.

What are you using for charge control currently?

Really useful thread this. One thing worth adding — those cheap panels often have higher temperature coefficients than branded ones, so you lose more output on hot summer days than the spec sheet implies. Fogstar and Renogy at least publish honest figures.

Also worth checking the actual cell count. Some budget 200W panels are using smaller/fewer cells to hit a price point, which shows up badly in partial shade situations.

My static caravan setup runs Renogy panels alongside a couple of no-name ones I bought as spares — the difference in cloudy-day performance is noticeable. UK winters really expose budget panels because you're relying on diffuse light almost entirely Nov-Feb.

Still worth doing on a tight budget though — just factor in ~30% haircut on the rated wattage and you won't be disappointed.

Really good thread this. One thing I'd add that nobody's touched on yet — check your actual open circuit voltage on those cheap panels before committing to a charge controller. I bought four "12V" panels that were pushing 22-23Voc each, and wiring two in series nearly cooked my budget PWM controller which was only rated to 50V input. Caught it just in time.

Also worth grabbing a basic clamp meter and logging your actual amps at solar noon on a clear day. Mine were hitting roughly 65-70% of rated output under ideal UK conditions, which honestly isn't terrible for the price paid. Just factor it into your calculations from the start rather than getting caught out when the batteries aren't charging as expected. @DefenderConvert what charge controller are you running?

@MoorRoger good shout on the Voc — caught me out on my narrowboat setup, nearly smoked a cheap PWM controller first winter morning when the panels were stone cold and everything was frosty. Swapped to a Victron SmartSolar after that, never looked back.

@DefenderConvert honestly your numbers don't surprise me at all. I'd say budget 80W real-world output from those "200W" panels on a decent UK summer day, less in winter obviously. Factor that into your battery sizing or you'll be running flat wondering what went wrong.