I run them all day everyday on battery. The dragonfly x2 is the best adjustable machine to push carts. Its the machine that made me put down my thunder/flite/fki/whatever else that is out and pushes pushes carts.
The swash compact is a close second on the adjustable cart machine list for sure. It's only drawback is the weight feels a little off for a few tattoos. It's easy to get used to thoigh.