a lot of those lamps run off a 6volt battery, but then, if it has a cigaret lighter conector, I think that may make it a 12volt. Best to take it apart and see what battery is in it, is it one of those cheap rechagerbal ones?
If so, I converted one into a lamping lamp, with a bigger battery pack
I linked up a load of 6 volt batterys for mine, but some one told me that if you use a 12volt, you just need to change the bulb to a 12volt bulb.
I dont use it anymore, but it did ok for a bit, still works now, but not as good as my blitz.