At first, I figured my 36v 20 ah pack, could possibly go 20,000 miles. 20 miles per cycle, 1000 cycles. Over the summer, I decided that might be a bit optomistic, since the last 500 cycles would presumably have less capacity than the first 500. By fall, reading about all the problems with many types of lifepo4 packs, I began to think that 10,000 miles would be a more realistic expectation, at least in terms of it being still able to do my pretty hard ride home. So I was thinking, maybe it will go 20,000 miles, but as soon as it can't get me 15 miles, I'll need a new battery or a booster pack to be able to make it home.
But, I was thinking that at about 1500 miles last fall. Now, with 3400 miles as of today, and still no hint of lost capacity..... I begin to wonder if I'll be getting a lot more out of this thing that I was thinking. 20,000 miles? 30,000 miles? who knows. But I'm getting pretty sure that a good set of cells can go an amazing distance. One stinker in there though, and its a different story. For once I'm lucky and have one that may last me 5 years, even at 4000 miles a year.
So I'm starting to think that yes, 15,000 miles out of a good lifepo4 pack is not a fantasy, but the expectation will still take most of us a few more years to prove. For a 48v pack, with perhaps 25 miles in it at 80% discharge, the number gets even higher, say 25,000 miles life expectancy. Ride slower, on a more efficient motor, and it goes through the roof. Say you have a 200-300 watt motor, and ride 15 mph all the time. Now you are looking at 30-40,000 miles. Wow, that will mean your battery outlasts quite a few saddles! I have to wonder, if not abused, how long does the motor last? A few bearing changes maybe, and a couple controllers, and your cost per mile could get too small to measure. Cool.
THE LIPO RULES. NEVER ABOVE 4.3V NEVER BELOW 2.7V DON'T PUNCTURE
Ideal charging /discharging range for Lipo, 3.65v minimum 4.1v maximum
See battery technology section, FAQ thread at the top of the page for lipo noob info.