Well... I'm lazy...
So I ended up getting the 8 new batteries and a small (ie normal sized!) Gel battery for running the 12V stuff of in trade for the other ones... Much easier to carry... Lets just hope I don't short any of them out now...
Altough I have a few other unmatched ones for some testing...
Tomorrow I'm gonna go stick my head in a old forklift and see that engine...