Originally Posted by
FletchCossie
Are bike batteries not 8v and cars 12v?? or am I barking up the wrong tree

Wrong tree I'm afraid.
Old Volkswagen Campers had 6 volt electrics, but that's about it.
Fudgey, as above, not enough Amps to get the car going, especially from cold. Plus bike batteries can be very expensive.
How about something like a Micra battery? Lot of Evo owners use them as they are small but still have ooomph!!
Si