I have TurnTech 5 Amp Lithium battery installed.
On the weekend, I had to kick it first thing in the morning and after my first stall. But after that, my bike started flawlessly in muddy single track. The fan was buzzing. The headlight high beam was on often and the the bike still turned over, even in gear.
I have not upgraded the stator yet.
This battery saved a couple pounds over stock.
It seems to be dead or weak shen cold but it gets stronger as it warms up...when it counts...when you are exhausted in the muddy single track.