The dash has "Motor" temperature and "Air" temperature, but the sensor must be under the seat or something because it goes up significantly when charging. I might be able to see what the battery temperature is by looking at the logs.
I cannot quantify the effectiveness of the insulation, but I do think it helped. Without it, the "Cold Batt." warning showed until the air temp went above about 50 F, while with it, the temp was at 42 F with no warning.