How many Mini E drivers have this problem charging from the 240 volt wall box in the cold? Mostly in New Jersey?
Here is what I am pretty sure is happening:
The AC Propulsion electronics (the big brass box under the hood) checks the voltage when you plug it in. If it thinks it is too high, it won't charge to protect itself, or it will start charging and then see the problem and stop.
Something about the colder weather (maybe combined with a low battery charge) is making it judge the AC line voltage (mains voltage) too strictly. I typically have over 126.5 volts at the regular outlets around the house. So at the Clipper Creek charging interface (or wall box), it sees twice that, which is over 253 volts. (Please Please DO NOT try to measure this directly if you are a civilian. There are safe meters such as the Kill A Watt which will measure a regular outlet and you can multiply that by 2 for an estimate.)
Normally I would guess the AC Propulsion box is happy if the charging voltage is below 260 volts, but in the winter that threshold has slipped down about 3% and it now thinks 253 volts is too high. Well, our local power company PSE&G does a very good job keeping the voltage up in central New Jersey. I don't think there really is a problem from the power companies' point of view until the voltage gets to 128 volts, but I am not having any luck finding a specification. I just remember that from somewhere.
I think I can prove this to Mini, although they can probably verify it themselves. Too bad, I was looking forward to the promised house call. But I am super busy at work right now so I probably would not have time to meet them anyway until January.
If you are one of the Mini E drivers with this issue, try turning on everything in the house before you plug in your E. The extra load should pull the voltage down a bit and might be enough to make the car judge the voltage as safe. Don't forget to turn things off again as soon as the car has been charging for 15 seconds, especially the stove or the dryer. I even ran the Microwave but be sure to put at least a cup of water in it, they don't like to run empty.
I switched back and forth several times, and the car would always continue charging when the line voltage was at 240 or slightly below, but back up at 253 volts it would either not start at all or only blink a few times and then stop.
After all the theories that have come and gone, I am going to be really embarrassed if this gets disproved. But I am pretty confident this time. The real test will be tomorrow after the long commute to and from work and the low battery charge.