My brother-in-law gave his 2006 CBR600 F4i to me (I have 2 now), and it has only 3,400 miles on it (and he was the 2nd owner). It goes without saying the battery was dead.
I'm not finding a LiFePO4 battery that fits the small compartment that can also provide the cranking power needed to start the bike. I did find some cells rated at 7.2 Ah in a 32700 size. I assume they could withstand the brief spike to 100A to start the bike, I just don't know how I'll keep them balanced.
https://www.amazon.com/Tenberly-LiFe...6391101&sr=8-3
Then there's these supercaps that are rated for 3.8v. That means only 4 in series are needed. Perhaps 4x 220F in series would be a good option for starting the bike? The data sheet says it has 100 mOhm resistance and is only rated for 15 A peak, so perhaps not a good option. 100 mOhm seems high when others are <3
https://www.mouser.com/ProductDetail...jpzEOaSw%3D%3D