I picked up one of the 'cheapo' ones at a truck stop a few years ago (I was on a 300 mile trip when my battery decided to go Tango Uniform).
The only problem I ever had with it is that I lost the charger & never got around to making a new one.
The best thing is to add a switched 12V power jack wherever you plan to store it in the VX. Keep it plugged in alla time & it'll always be ready for you.