As an experiment I ordered a 48V 20AH LiFePo4 battery pack from Yesa and I installed in on my Evader 1000 electric scooter. It ways about 30 lbs and I used it to replace 4 SLA 12V 45AH batteries which weighed together around 140 lbs, so my scooter is now about 110 lbs lighter. One problem I have found is that when I accelerate hard, the Evader pulls more than 60A which is enough to pull the voltage below the low-voltage cutoff and the pack shuts itself down. It then stays down for some period before waking up again, it seems. I have asked Sam at Yesa for advice on what to do in this situation.
I have not done a range test yet, and thus far I have only gone a couple of miles at a time. The scooter feels much lighter and the top speed seems to be up 1-2 mph to around 33 mph.
More reports as I gain more experience.