The way I understand it the cold actually slows down the chemistry in the battery reducing its capacity so I don't think that adding a trickle charge will improve things. Unless the vehicles are driven rarely and then yes, at least the batteries will be at maximum charge when needed. Daily driven cars should be fully charged from use. That said I have used "Battery Tender" brand trickle chargers on motorcycles and such and they work as advertised. Plug it in for cold weather starting. RT

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