Hi. I have an option of choosing between a 36V 10AH Lithium ion (polymer) battery and a 36V 8AH LiFePo4 battery for an electric bike. Cost difference is negligible. Range is important to me. Can anyone tell me what difference in range I can expect between 8AH and 10AH batteries? I am using a 200W motor. Would welcome your thoughts on the subject - I am aware of the inherent safety and reliability advantages of LiFeP04.

1 mile per ah...always go with more

Your LiFePO4 option will contain 288 watt hours of energy, whereas the polymer option will contain 360 watt hours which is considerably more energy, and will get you 25% further than the LiFePO4 option (mathematically). Polymer batteries from good manufacturers are safe and trustworthy if used properly and not mistreated.

Consider the long term cost of the each chemistry, if the number of recharge cycles of LiFePO4 is significantly greater, the cost difference may not really be negligible.

Still, as they used to say for cars, there's no substitute for cubic inches.

What sort of cost/AH are you facing?

Thanks everyone for your help so far. I didn't realise the difference between 8AH and 10AH would be as much as 25% - that is certainly worth thinking about. Also the cost angle is important - the LiFeP04 is rated for 1000 recharge cycles and the Lithium Polymer at 500 recharge cycles.

I would go for the 10ah hands down. That extra range is nice to have. It'll weigh 2 or 3 pounds more and thats not really a big deal.

What would a 12v 80Ah battery give you? What are the draw-backs of using a 12v system instead of a 24-48v system?

I've been told to think of the voltage as the average speed you'd be cruising at, and the AH as the capacity of the battery. So.. with 12v-80ah maybe you won't go faster than 10mph but you'll go for like all day.