Interesting that electricrider is now selling lithium. They used to be the last die hard advocates of lead acid, and had provided some good pannier racks for carrying it all.
Dissapointing, is that they seem unwilling to disclose the c rate of the cells they use. This never mattered with lead because there is not a lot of variation in c rates with lead. They do have a link to a page, that basicly says don't get the lithium to run a 40 amp controller and a big motor, (thier phoenix model)
With lithium though, lifepo4 can be anything from 1c to 20c. It would be nice to know what you are getting eh? I'm less familiar with limn, but I never heard of any that was much better than 1-3c.
So though this is a source for a 72v pack, I would not be calling it a real substitute for the perfromance of 30c lico (RC lipo)
There is simply no way a 72v 10 ah pack from electricrider is going to run a 40 amp controller without risking damage to the battery. So you'd have to carry more of it, and destroy the handling of the bike on the trickier parts of the trails. What works on street or riding dirt roads fails on tough singletrack.
EDIT
Reading back, I see I may be confusing you with another thread. What exactly do you need to do? Is this for street or dirt? How many amps controller? Maybe 72v 10 amps is plenty for the motor you will be running.
Even for street though, carrying more than 15 pounds of battery tends to unblanace the bike too much if carried on a rear rack, and more than 72v 10 ah, 48v 15 ah, or 36v 20 ah never fits in the front triangle of most bikes.
So you end up right back where you started. You want to carry about 800wh max, and if you want power, you need a good c rate battery. A123's, RC lipo, etc. not 2c stuff. If you wanted 36v, then it's easy to carry enough 2c battery to have some amps.