Went to the storage unit to exercise the unit, put the key in, turned and yep,,rrrrrrrrrrr,clk,clk,,, battery dead,$!&++,  not having all my tools took about 45mins to pull out old battery. I hate these modern batteries, the old ones would at least give you a little warning before going kaput.
  Went to local auto zone got a replacement and some proper tools. The old battery was the original from 2008 so got pretty good use out of it. Was some slight swelling on one side of battery.

    Upon disconnecting the cables, saw that they would be a problem when installing new battery. So took some plastic ties and tied up the battery cables. Note that our cables are extra large for all the extra hook-ups on our battery system.

Yellow tie is holding the negative, had to take a couple of black ties looped together to hold back the positive cable. Used 10mm for battery cables.

You can see the rust and some acid spill from old battery.

Went ahead and removed the battery tray to clean it up. Some damage from acid on mount. Cleaned both areas up. 

Clean up the mount tray. I first cleaned with brush, wiped with oil. Wiped it down then sprayed on some of that battery corrosion gel on the nuts, screws, did the same for the mount area. Used 13mm socket. 

New battery

Pic showing the battery clamp that goes in the back of the battery to hold it down, Cleaned and sprayed also. Used 5/16 socket.