Been running a 200W panel (2x 100W Renogy monocrystalline in series) on a Victron SmartSolar MPPT 75/15 in my Sprinter build for the past year and had no real complaints. But last weekend I helped a mate set up his first system — budget build, 100W panel and a no-name PWM controller he picked up off eBay for about a tenner.
Even on a crisp, clear January day with decent sun angle for the time of year, he was barely pulling 3-4A into a 100Ah AGM. I stuck my phone on the Victron Connect app on my own van parked next to his and I was pulling nearly double that from the same sky. The PWM was showing panel voltage fine, just seemed to be throttling everything to death. Ambient temp was about 3°C.
I know PWM vs MPPT is a well-worn argument on here, but I'm specifically curious whether anyone's seen PWM units behave worse in cold weather rather than better — because in theory cold panels produce slightly higher Voc, which a PWM just clips anyway. Has anyone measured this properly or swapped out a PWM for an MPPT mid-winter and logged the before/after numbers? Wondering if there's a solid case to make to my mate that the £40-50 for a decent MPPT is worth it even on a small system.