Anyone else running a Victron SmartSolar alongside cheap eBay panels — what MPPT settings are you using?

Finally got my roof setup sorted on the van — two 200W "brand X" panels wired in series off a dodgy eBay listing, feeding into a Victron SmartSolar 100/30. Panels are supposedly 24V nominal but the open-circuit voltage is listed as 45.2V each, so 90.4V combined in series. Staying well under the 100V input limit but it still makes me a bit nervous if we get a proper cold snap.

I've had the controller set to the Victron default absorption/float for a 100Ah lithium (LiFePO4) — absorption at 14.2V, float at 13.5V — and it seems to be working fine. But I'm seeing the MPPT jump around a lot mid-morning, especially on partly cloudy days. Not sure if that's just normal behaviour or if there's something off with the panel specs I was given. The VOC and Isc numbers on the label don't quite match what I'm measuring with a multimeter.

Has anyone managed to nail down accurate settings when the panel datasheet is basically guesswork? Wondering if I should just run the BatteryProtect app and log a few days of data to see what's actually happening, or if there's a smarter way to cross-check dodgy panel specs. Any Victron Connect tips welcome too.

Wez1993 | Posts: 847

@LochSeeker Nice one, sounds like a solid little setup! With those mystery eBay panels I'd definitely grab the actual datasheet if the seller provides one, but if not, derate the Voc by about 10-15% from whatever's printed on the back label — they often overstate it a bit.

For two 200W panels in series you want to make sure your combined Voc stays comfortably under that 100V input limit, especially on a cold morning (voltage spikes up significantly in the cold, worth remembering for winter).

On the SmartSolar I'd leave absorption and float at defaults initially and just monitor via the VictronConnect app for a week or so — it'll tell you far more than any preset will. What battery chemistry are you running? That'll matter more for tweaking the charge profile than the panels themselves tbh.