Use a piece of cardboard to fit the coil next to the magnet, works well as a spacer.
If you use the appropriate charger and battery pack from the same seller it should all work fine.
I've had mine for about 12 months and it runs fine, I used the complete kit but the lights broke and werent too strong so I wired 2x3V flashlights on the front, soldering wires to where the batteries should go.