That 8 AH SLA pack won't be anywhere near enough ....not even close. You'll need at least 15 AH in SLA (lead acid) to get decent range. And about 10 AH of Lithium to get good range.

And your probably better off with a aotema kit from hightekbikes.com for $330 rather than that one. Or check e-bikekit.com too for some good deals.