2nd battery location?

[Having A Ball]

I am sure I am over thinking this but,,,,, here we go!

Just bought my first 2013 323qb 5th wheel and the battery is up front and is mounted in a flush (with the floor of the bay,sort of speak) battery box with a vent lid. My question/concern is adding a second battery where it will be safe and secure. The plastic material the floor is made of seems light weight. I would like to just screw a new battery box beside the current location hook it up and go? should I worry about a second vent lid? anyone else have an issue?
Just behind the factory battery is my water pump and waterlines. I have the room just not sure about the weight of a second battery that close to the factory one ( both 12V Craftsmen marine deep cycle ) I am also including a kill switch with this mod as well.

thanks for any advise,
Rick

[sail2liv]

Why do you need a second battery? My 5 er came with a 27.....and so far no need for second one in system....have carried a 31 in the basement and a 24 sitting next to the factory installed one in a loose battery box....always charge in ventilated area. Have set of jumper cables if need extra juice when boon docking for factory system....and use the 31 in main basement under laundry chute for inverter if need TV or apnea machine....not sure how much boost the TV battery gives system, but some say you can cause that battery to go dead....have place in TV for second battery if that ever happens....and the 24 in the box is not too heavy to move to jump off TV if that one goes dead.....good luck....I would think a generator would be a better investment if you need the juice....I carry a champion in back of truck all the time....the extra batteries are for Walmart or a place that gen noise would not be appropriate....I probably will consider AGMs when these go bad....from a gas standpoint.....but for now the 31 is ventillated with both basement doors open if have to charge in place....but so far am able to just set it on the ground as with the one in the front....my inverter has alligator clips that attach to the 31 ...

[Having A Ball]

How long do you last with just one battery? No gen or recharging .