VFD and Car Batteries
If it is any type of industrial VFD, it is probably looking for either 240 VAC or 480 VAC.  Low horsepower VFD's can almost always run off of single phase, but you still need to get the internal DC Buss up to about 340VDC or 650VDC, so 48V won't do it.

Inexpensive fan/pump type VFD's generally don't directly expose the DC Buss connections, but they are easily available.  Even if applying the proper DC voltage there, you will have to come up with a precharge circuit to bring the buss capacitors up slowly.