RV Repair: Adding 12V Battery, 12 volt appliances, amp hours

Question
I have a 1985 5th wheel by KIT. I would like to add a second 12V battery. Is this this a good idea and if so how do I cannect the batteries?

Answer
Ed,
  If you do a lot of dry camping then yes it is an excellent idea to add a second battery as it will double the amp hours you have to run your 12 volt appliances.  You will want to hook the batteries up positive to positive and negative to negative.  It is recommended that the positive to the coach be hooked to one battery and the ground hooked to the other, but I really don't personally believe that it really makes all that much difference if you don't.  Also, if the existing battery is more than a year old it is recommended that you put two new batteries in because hooking a new battery to the old battery will drag the new battery down to its ability to hold a charge.  I hope this helps and good luck.

Darren