I power mine using 9V LIon DVD player batteries (aka Walmart batteries). Went to Rad shack, got the adapt-a-plug set, with a "B" tip and an "F" tip.
ALWAYS plug in the cable to the Denecke first, then the battery. When plugging into the Denecke you can get a dead short for a millisecond, and the battery might not like it. These DVD player batteries will typically trip a little circuit breaker (or something like that), and then you would need to plug in the battery charger to reset it. If I plug in the Denecke first, and battery second, I've never had a problem.