Also the action of significant discharge or charge will inherently warm a battery (you can feel it in your phone after a fast charge or using an intensive app like a game) so if you're actively using the van and leisure electrics that will all help keep the cells warm. I believe some BMS use a low rate of charge to self heat the cells when it's just mildly cold rather than having additional heaters, but that only works for a few degrees below freezing.
