amp hours are important, but so are amps.
the 10,000mAh (10Ah) pack here ...
http://www.batteryspace.com/index.as...OD&ProdID=3002
... claims a max discharge rate of 10 amps. Not good, unless you have a 200 watt motor.
Better to buy this one:
http://www.ebikes.ca/store/#Batteries
(sorry I didn't direct-link you to it before)
where it says "c rate" that means you multiply the number of amp hours by the "c rate" to get the number of amps it's good for. Also notice the price.