Taking a closer look in the right hand footwell in my C5 last night I noticed that it has holes for both ends of the battery strap, rear battery "foot" and a bracket to hold an additional keyswitch. There's also a sticker on the central tunnel advising to turn on both batteries if two are connected.
Does this mean that it was originally fitted with a dual-battery setup? Or where they like this from the factory, then a second keyswitch purchased and fitted if required?
It doesn't currently have dual-battery electrics, would it simply be a matter of getting another keyswitch assembly and "doubling up" on the connections so the two batteries work in parallel?