Use these in airplanes to save some weight?

We usually use two independently switchable batteries (at least I do)
so the self-protection low voltage feature may not be a problem.

http://eetweb.com/power-supplies/lithium_batteries_3411/

http://4xspower.com/products/

Perry Mick

That is the way Mike set up the RV4. Is 28 AmpHr (both batts.)
enough for starting?

Paul Lamar

I currently use two Panasonic sealed lead-acid batteries. Just ordered
replacements as the existing have been in place for many years. Digikey
part number P049-ND, 28 AH each. I can independently switch in either or
both, but I always start and run on both. I think I did start it long
ago on one battery. Invoice from Digikey says 46 lbs. shipping wt. for
the two batteries.

Perry Mick