Kurt just finished his Carbon Cub EX and this is what he did for a starting battery. Here is his PM to me.
Thanks Kurt
I am currently in the testing phase of a battery re-design for my Carbon Cub EX. I installed a 12 cell Lithium iron battery with a 10 second drain of 360 amps. I started the 180 HP engine perhaps 15 times with this battery. It never let me down, but a couple of times it was just barely OK. My solution was to install the second Lithium Iron battery. They are connected in parallel and they REALLY spin the 180 HP engine. Mitch has a 5 second video of me cranking the engine with the ignition breakers open. Each battery weighs 2.11 lbs for a total of well under 5 lbs.
I moved my ELT to the overhead bracket in the upper shelf baggage area and it gave me plenty of room under the seat to locate both batteries there. I have five hours on the two batteries and it is one of the strongest starting planes on the airport. Also, the batteries I am using are Moty Design batteries. The two batteries yield 720 amps for ten seconds, but it always starts in about two seconds. Hot or cold makes no difference. Any questions?
Kurt