Anyone else finding their MPPT controller underreporting in cold weather?

Noticed something odd this past week during the cold snap we had here in the Midlands. My Victron SmartSolar 100/30 has been showing panel voltage around 10-15% lower than what I'm getting when I measure directly at the array terminals with my multimeter. Panels are two 200W units wired in series, so nominally 44V Voc each, giving me ~88V open circuit. Multimeter's reading about 85V on a clear morning, but the Victron app is showing closer to 74V.

I'm wondering if this is a wiring loss issue or whether the controller itself is doing something funny in the cold. Ambient temps have been dropping to around -3°C overnight and the panels are on the roof of a static van, so not much airflow underneath. Bluetooth connection to the app is solid and all the firmware is up to date.

Has anyone else seen this with Victron kit specifically, or is it more of a general MPPT thing? Curious whether it's worth running a longer logging session to see if the readings converge once the panels warm up mid-morning.

@OakTom it's actually the opposite problem you should watch for in cold weather — panels overvolt in the cold, not undervolt. VOC rises significantly below ~25°C (the STC rating temp).

What you're more likely seeing is the MPPT actively clipping or the SmartSolar displaying operating voltage rather than open-circuit. Are you measuring VOC with panels disconnected from the controller, or under load?

Also worth checking — if your panels are frost-covered or have condensation on the cells even partially, that'll massacre your measured output. Had this constantly last January with my garden office array. Looked fine visually but numbers were rubbish until 10am.

Download VictronConnect and check the history graphs. The SmartSolar logs daily yield and panel voltage peaks — far more reliable than spot measurements in variable winter light.