The DC motors in modern furnaces and boilers are, oddly, designed to operate on A/C. The advantage of DC motors in these applications is that they can be PWM controlled, so the speed is infinitely variable. Incoming AC current is electronically rectified to produce a PWM feed at the desired duty factor. So no, you can't run them off batteries.

I use pumps with DC motors (Viridian 2218's) on my boiler. The pumps have ECM logic cards that continuously adjust the speed so that the return water is 20 degrees cooler than the source. This allows the pump to run almost continuously and produces a very even heat. When they start up they are at full scream, and then slow down as the spent water comes back around. I've been very happy with them.