Sudden unexplained drop in SOC?

I live in Des Moines, so probably pretty comparable temps to Chicago. We had a temperature drop last night and it was around 19 degrees this morning on my short ride into work, so maybe that is part of it.

I have a new MB battery ready to go, but the last time I checked, the diagnostic tool said my original battery is still good. I’ll check it again and maybe just replace it out of caution. I wonder if a weak 12v battery is also part of the reason I’m getting such terrible range in the winter? 35-40 miles average per charge, or less if I run the heater.

No heated seats, unfortunately. I use the heater sparingly. I dress for cold weather, but there are still times when it’s necessary to run the defroster. Even when I’m not using the heater, I’m lucky to get a 40-mile range in winter. My HV battery has degraded about 10% and it’s more noticeable in the winter. Hopefully the initial rate of degradation has slowed down so it won’t drop by the same amount over the next seven years.