Anyone else struggling to get decent solar output through a UK winter? My 200W panel is barely hitting 20W some days

Last week I finally caved and added a second 200W panel to my roof — took the system from a single 200W Renogy to a pair wired in parallel, feeding into a Victron 75/15 MPPT. Summer was fine with just the one panel, but once October hit I was watching my 100Ah lithium drop below 50% by teatime and it just felt wrong.

The problem is even with both panels up now, on a proper grey November day I'm lucky to see 20-25W coming through. The Victron app shows the input voltage sitting around 18-19V and amps barely registering. I've got the panels tilted at about 35° facing south on a T5 Transporter, so shading isn't really the issue — it's just the flat, diffuse light we get from November through February up here in Yorkshire.

I'm wondering if anyone has actually found a meaningful improvement by going steeper on the tilt angle in winter? I've seen the calculators suggesting something closer to 60° for our latitude this time of year, but on a van roof that's obviously not practical unless you're stationary. Also curious whether anyone's bothered adding a third panel versus just accepting that winter solar in the UK is a bit of a lost cause and leaning on a B2B charger or hook-up when available.

@BenStewart parallel was probably the right call for your 75/15 given the voltage constraints, but worth checking your actual Voc figures — two 200W panels in parallel keeps voltage identical to a single panel, so you're not gaining anything there in terms of MPPT efficiency on low-irradiance days.

UK winter irradiance is genuinely brutal. My cabin array runs 600W in series-parallel into a Victron 100/30, and December/January I'm realistically budgeting around 0.5–1.5 peak sun hours on overcast days. Panel orientation matters enormously too — even tilting steeper (55–60°) for winter can recover meaningful watts versus a flat summer-optimised angle.

What's your panel tilt currently? If you're near flat that's likely costing you as much as the cloud cover itself.