Got a sow about to farrow. Chap we got her from said we need to set up a heat lamp for the piglets to sleep under. No mains supply. Colleague has cleverly come up with a dog heat mat that plugs into fag lighter and plans to splice the wires to go on a battery. Will this give them the heat that is required in the same way as a lamp ? Not sure how long a fully charged battery will last. She is in a sheltered pen in a barn, is this heat actually needed ? GOS pig. Thanks.