Lithium is nice but has become real pricey for me. Have you ever had SLA for comparison?
I decided to go with lithium iron phosphate because it's actually very cheap on a per-mile basis. This is because you don't need as many amp-hours*volts to go the same number of miles, plus lithium iron packs tend to last for over 1000 charge cycles, while lead acid lasts for a few hundred. I've never had another ebike battery. but for my use, SLA is a poor choice-- I live 17 miles from work and have to carry the bike up some stairs to park it. I feel like I got a good deal because I bought from
www.yesa.com.cn for $330 and got a battery which I think will last 2 years in heavy use. (1000 cycles, 17 miles per cycle, 2 cycles per work day, which is about 1 cent per mile). If it only lasts 1 year I won't cry too hard as that will be 2 cents per mile in battery cost. With a lot of luck, it could last 5 years/2500 cycles!
The motor is from cyclone and it's the 500w kit. Great kit if you want power on steep hills and on flatter ground.