tank pads 12v or 120v ?

honda1 wrote:
are tank pads 12v or 120v , just wondering if going down road will heat off 12v batteries .

Of course, that's the raison d'etre of 12 vdc tank heating pads, for those times you don't have shore power available, but of course their effectiveness will be determined by the capacity of your 12 vdc system to supply power to those pads. For those who always do have shore power then 120 vac is the more logical choice.