I cannot prove it, but I think it has more to do with a detection issues of some sort, than a low battery. If the battery is cold, it disables a bunch of stuff (note the technical term).
I have had the warning on a few occasions throughout this winter. To test my theory, I never charged the battery, and as soon as the temps go up, the warning goes away and everything is good again. To note, I have never had an issue starting the car even when the temp went down to -35C. The limit temp seems to be around -20C.
When the temp was around -30C, I drove at least 900km in a day and the warning remained. I would assume the battery had enough time to recharge on such a long trip. Then when the temp went up, whaddayya know: Gone.
Finally, in the past week, when I left home in the AM, temp was at -25C and as soon as I reached work, the warning showed up. The temp went up throughout the day to -8C and when I left in the afternoon, the warning was gone, everything worked with the car staying in the parking lot for 12 hours. I doubt it recharged itself...
This is puzzling as hell to me. And my dealer installs trickle charger on every car they deliver, so they know there is an issue somehow. But even when I had the warning last year and I used the charger overnight, it would remove the warning, but it would always come back on cold days as soon as I reached work. So that didn't work either.