No airlines for me since leaving my ramp rat baggage thrower (yes, we threw it...) position at Continental while they were still at Stapleton.
Just a po' old Cessna driver here. (Co-owned 182 based at KAPA.)
Congrats on the Passport! Just remember when stuff breaks to take a deep breath and get out the duct tape. No A&P nor any build standards like in airplanes!
(No $950 for three aileron hinge halves at annual inspection time nor $150 dollar rubber donut engine mounts either...!)
For the person who asked how to add a battery... gkainz covered the hard part. Proper boxes bolted down so they don't go anywhere. Having a 100 lb battery become a missile smashing everything in its path, during corners or hard braking or acceleration is bad juju. If you can keep them from wandering around that's well over half the battle.
Hooking them up is relatively simple, electronics-wise. Parallel if 12 Volts, two in series if 6 volts.
Having two batteries of same type and age is generally a good idea also since you don't want one older worn out battery and one new battery.
But keeping then from moving is the important part at first!