Picked up a Renogy Wanderer 40A MPPT back in autumn to run the shepherd's hut setup — two 200W panels feeding a 200Ah Fogstar lithium. Worked a treat through September and October, but since the temperature dropped below 5°C it's been chucking random error codes (E3, occasional E1) and going into protection mode mid-morning, right when the sun's actually doing something useful.
Panels are wired in series giving me around 44Voc, which should be well within the controller's 50V input limit. Battery connections are solid, BMS hasn't complained once. I'm wondering whether the Renogy is just not handling the cold the way a Victron SmartSolar would — the low-temp charging cutoff on the Fogstar is set correctly at 5°C, so that shouldn't be triggering it.
Has anyone else had grief with Renogy MPPT units in a UK winter? I'm half-tempted to just swap it out for a Victron 75/15 or similar and be done with it, but the hut's power demands are modest enough that I'd rather not spend £150+ if there's a simple fix. Could the issue be something as straightforward as the panel Voc spiking higher than expected on a really cold clear morning?