on the topic of connecting 2 batts in stead of 1 for future preference, all you have to do is cut the battery cable on the positive and negative, then fit a terminal block, you will need to get 2 plugs (that the battery plugs into) and then put the 2 positive cables to the positive going into the positive side of the terminal block, then do the same on the other side with the negative

sorry if that didn't make much sense at all, or if you already knew lol
cheers,
Matt
Edit Matt can you use a spell checker please Brel