1. I'm in western Washington and the car is garaged, so I'd guess the lowest temperature was probably 50 degF and the average around 60 degF. 2. I didn't try to check the SOC while I was away. I've read on this forum that the car stops broadcasting after a week. Sorry I can't add more data to that.
Online: Amazon and even Deltran’s own website always have them. Brick And mortar stores: most motorcycle, snowmobile, or RV stores will have them. The only brand that I truly trust to be set it and forget it for battery maintenance without eventually cooking the battery is Deltran. It is the only charging battery maintenance device I will ever use, period. They are definitely not the cheapest but will save you money almost right away on batteries by making them last. One killed battery costs way way more than the cost difference of Deltran vs a cheaper brand.
I didn’t mean that Deltran was discontinuing them, just that my local HD was clearing them out. Posted so that others might be able to get the same deal at their HD. $40 is cheaper than any place I could find on line. Also, I found the extra connector for $5.39 with free shipping on eBay.
Thanks for the tip, @KentuckyKen . I've never used a battery tender and didn't need it this time, but it could come in handy in the future, so I'll check out our local Home Teapot (as a former neighbor calls it).