All I know is the battery that was fitted to my Plus 8 in the UK was smaller than I would fit to a mini, so on arrival in NZ with it flat I changed to an Odyssey PC-950 AGM battery which is mounted lying on its side behind the drivers seat , of course that was the original spot on my model year and I only had to adjust the tray size , you may not have the space in the GEMs under bonnet models . It really flings the engine over and hasnt given a moments issue.