question

Update - I waited for it to warm up (now 4 degrees) very sunny out in the UK today!

Switched the DC breaker, on - voltages totally fine;

put the washing machine on, figures all looking fine.

I presume it's still worth sorting this though, otherwise il be forced to turn off my system during such weather rather than letting it manage itself with suitable tolerances...

You have to distinguish between Open Circuit Voltage Voc and the Maximum Power Voltage Vmpp.

The Voc is always higher, and in this case for this modules it is definitly way to high. It is 49,5V @ 25°C. And at 0°C it is already 52,6V (0,25% of increase each degree). And this will in some point destroy your MPPT as it was already mentioned above.

The point is, that this Voc is the the voltage the MPPT "see" first time before it can start to search for a Vmpp (to say it in simple words). If it once finds a maximum power point, the voltage is dropping down to Vmpp and this is what you see in the remote console when there is also power drained out of the modules.

It's up on you, put I also would strongly recommend to change to a 2s3p configuration!

Just to let y'all know - I updated the panel wiring to 2s3p configuration;

Peak voltages now WELL below where they were and the 150V MPPT maximum. I have two panels that can get shaded in the winter so paired them together and I seem to be getting better evening performance because of it.

When I originally set this up I didn't realise at all that panel temperature would play a part in affecting the voltage. I just checked the VoC values on the spec sheet, saw they were just under 150v in a 3 panel string and thought that was ok.

I don't see this talked about much online (I didn't notice it) but it certainly does play a considerable factor, maybe in some climates more than others.