Thanks, Interstate guys, for posting your experiences with coach battery replacement and solar upgrades.
Today I got two Lifeline GPL-6CT's stuffed into the battery box of my Lounge model. It was a bit of a squeeze, but they fit, and now I have 300Ah ready to go. The old Discover EV24-A-A batteries wouldn't hold any charge at all after just 22 months since we bought the rig new. We were pretty rough on them, though, running them down to zip a number of times.
I also installed a second propane solenoid switch in the control panel area, and added a 100W solar panel from AM Solar on the rear roof (ditched that crazy round digital TV antenna - never got more than one or two oddball stations even when parked in large cities!)
Just a couple notes for those considering doing these same ideas floating around for us folks who like to roll 'unplugged':
1) the second cutoff switch for propane - easy access to wire '68' is available in that thick bundle under the curbside cup holder - no need to grovel around under your rig (see photo). Just find the red wire marked with the number 68 - cut it and connect the wires for your switch. Route the wires up and around like others have done and put in a nice lighted rocker switch next to the water heater switches. Radio Shack has a nice switch for $5 - just add a ground wire from the switch to a bare metal lug you add to the Sprinter metal wall behind the control panel and you have a nice indicator light to tell you your propane is on and flowing.
2) the GPL-6CT's - I guess I'm one of the guys blessed with a deeper battery box, since I made them fit. However, I don't know what folks are saying about adding a short cable to connect the two 6V Lifelines in series - there is more than enough cable in that battery box when you change from parallel to series connection! I ended up with several extra cable pieces of red conductors. Just orient one battery opposite the other and you can connect them in series with the cables from the factory if you do it right. You will need to cut off the big 'car battery' terminal and replace it with a lug snitched from the other red cable you won't need.
I removed the bottommost plywood pad (from the battery box) to squeeze out another half-inch, and raised the battery cover lid up an inch or so by drilling out the two rivets attaching the lid hinge and re-riveting the hinge to be unfolded in the latched position. That allowed me to still use the factory battery box cover (adjust the latch a little) and it all fits just nicely under the seat. I didn't bother with either of the battery hold-downs; just stuffed in some closed cell foam blocks from the battery shipping cartons to make the batteries stay nice and snug in their little house.
Speaking of batteries, I received a great price and great customer service from Marc at Centex in Texas. Authorized Dealer Lifeline GPL-6CT Battery $ 360.00
3) added solar - Roger at AM Solar in Oregon was a great help, and now I have an extra 100W (added to the factory 50W panel) to get my Lifeline's charged. I wouldn't recommend digging out all the roof goop to get at the wire bundle (the wires for the power awning, backup camera, TV coax), but instead drill a new hole for solar panel conductors with suitable weather seal. I dug out that stuff and routed the new 10AWG wire though the same batch of wiring, but it was a hassle. The wires run down the curbside rear pillar of the van just nicely, coming out near the battery box and into the wiring nerve center under the couch. Piece of cake to wire it in, since the factory solar panel wires are sitting there staring at you in the same area under the couch (yellow and green wires - yellow is labeled 'solar').
AM Solar included a 10AWG wiring kit with 15' of wire - I had to snip off just 6" of each - that worked out well. Goodbye to that goofy 'is that a satellite dish?' antenna that never worked well (yes, I switched on the booster. Anyone else get meager reception like we did?)
Thanks again to the many guys who forged ahead before me and shared their hard-won wisdom....