I do remember all the likes and I was excited for the opportunity the isolator provided but when I put thought to action it didn't work for me lol. So I needed to confirm with all the awesome people on here.
I do have a port for a charger for the auxiliary battery using a boat trolling motor plug. I will probably add another for the main battery so it will work with my charger. It does not get this cold in MO often and we have spent almost a week in the negatives during the lows of the day. I hate cold but I love snow and MO does not give much snow. But MI snows are beautiful.
If you have a Tru battery isolator, you won't need to add a second charging jack. That assumes that battery the jack goes to is in reasonable shape. As soon as the battery "under charge" gets to about 13.2 volts, it will pass a share of the charging current over to the second battery. Tru suggests connecting the charger to the aux battery. So you should be good. Just get a charger on there.
Now think about all those Tesla owners back east who have had to abandon their cars as the lithium batteries won't accept a charge if it's too cold. EV's a workable thing?? Yah, sure, you betcha . . . not.