Picked up a cheap 200W panel from Facebook Marketplace — worth it or waste of time?

Got a similar bargain last year — a pair of 175W panels off a local lad who was dismantling a static caravan setup. Paid about £40 for both, which felt like a steal at the time.

Honestly? Mixed results. One of them performs brilliantly and sits on my shepherd's hut roof doing exactly what it should. The other one had clearly been walked on at some point — you couldn't tell from the outside, but the output was noticeably low. Ran a basic shade test and it was obvious something was wrong internally. Ended up using it as a partial contributor rather than a main panel.

A few things worth checking before you commit to using it:

• Visual inspection — look for microcracks, delamination, or discolouration (hotspots can leave yellowish patches)
• Voc test with a multimeter — does the open-circuit voltage match what's on the label?
• Seller's story — caravan/shed removals are usually fine; "found in a skip" is more of a gamble

The cheap panel gamble really depends on what you're hooking it up to. If you've got a decent Victron MPPT handling things, a slightly underperforming panel won't cause drama. Chuck it through a dodgy controller though and who knows.

What did you pay for yours, and do you know anything about where it came from? That context makes a big difference to whether it's worth pursuing or not. Others on here have had brilliant scores from Marketplace — would be good to build up a bit of a picture of what makes a good second-hand panel buy versus a dud.

@CamperClive the price is right but secondhand panels are a proper lottery. Main thing I'd check is whether it's got microcracks — lay it flat and look for hotspots with a thermal camera if you can borrow one. A degraded panel might still work but you could be looking at 140W actual output from a "175W" unit.

Also worth sticking a multimeter on it in full sun — Voc and Isc should be printed on the label. If the numbers are way off, walk away.

The real killer with cheap secondhand panels isn't the panel itself, it's dodgy junction boxes and corroded connectors. I've had MC4s that looked fine but were arcing underneath. Replace them if in doubt — they're pennies from Amazon.

Not saying avoid it, just go in with eyes open.

@CamperClive £40 for two panels is basically free — even if one's a dud you're still laughing.

Main thing people forget to test: Voc and Isc under load, not just "does my cheap multimeter show volts." A panel can read 20V open circuit and still be absolutely cooked internally with microcracks that only show under actual current draw.

Grab a basic clamp meter, chuck a known resistive load on it, and compare against the datasheet. If Isc is more than 10-15% down, walk away or price accordingly.

Also worth noting — secondhand panels wired into a decent Victron MPPT will at least tell you exactly how badly they're underperforming, rather than a PWM controller just quietly weeping in the corner.

@CamperClive bought two knackered panels off a bloke on a narrowboat last summer — turns out "200W" written in Sharpie on the back isn't quite the same as a spec sheet. 🤦

Slap a cheap Victron SmartSolar on it and check what you're actually getting vs what the seller claimed — the truth comes out pretty sharpish when your batteries aren't charging past noon.

@HiluxLife that Sharpie story is painfully relatable 😂

Quick question for the thread — how are you lot actually testing these secondhand panels before committing? I've got a static caravan setup and picked up a couple of panels recently but I'm never quite sure if I'm getting a true picture of output.

I've been just chucking them on my Victron MPPT and watching what the controller reports on a clear day, but I'm aware that's a pretty rough method. Is there a better way without shelling out for proper test equipment?

Also does shading damage matter more on older panels? One of mine has a cracked bypass diode apparently — someone mentioned it but I don't fully understand what that actually means in practice for real-world output.