Battery wire

[Scouser]

Hope someone can help me out here, I am about to split my battery packs from stick to saddle layout. A pretty simple task but I was wondering whether the thickness of the wire is an issue. The wire that connects the battery to the Deans plug is pretty thin but the only wire I have here is the 12g stuff which is considerably thicker. Will this cause any problems? If so, where can I find the thinner stuff as all i can seem to get in the LHS and all the internet stores is the same as I already have! Any help much appreciated.
Cheers, Jon.