bumper,
Look in Resources & EV Related Parts in the ONLINE MARKET section under the Board index. There is a topic called "Battery Packs - Where to buy them. That topic will give you some links to e-bike kit sellers that also sell batteries.
The experimenters here at Endless-Sphere are always pushing the limit on high power systems. Some are running 72V with 40A controllers, or even higher. Many build up their own battery packs from individual cells. However, the average e-biker here in the US would probably be satisfied with a 36-38V system with a 20A controller. That type of system is right at the 750W legal limit for unlicensed electric bikes. As such, e-bike retailers tend to stay within this limit to avoid legal difficulties.
Justin at ebikes.ca is a good source for NiCd and NiMH batteries. He also sells a pretty good Li-Mn 36V 10Ah pack for systems limited to 20A controllers. Lithium cells are lighter than NiCd and NiMH but need added electronics for low voltage cutoff and cell-to-cell balancing (battery management system (BMS)). Justin's Li-Mn pack comes with a BMS.
LiFePO batteries have less sag than Li-Mn batteries and have the potential for 2000 charge-discharge cycle life. They need electronics for low voltage cutoff and cell-to-cell balancing. The "Ping" packs are available at a good price. Although they are held together with duct tape, they seem to hold up pretty well. However, their continuous discharge rate is not as high as the very top-brand cells. You need to compare your controller max Amps to the continous rating of the battery pack. For example, a 10Ah pack would probably be limited to a 20A controller. Search for "ping battery" here on Endless-Sphere to find out more about this seller.
The LiFePO 36V 10Ah pack at E-bikeKit.com has really nice packaging. The E-bikeKit folks are working hard to refine their design using feedback from people here on Endless-sphere. I believe this battery would also be limited to use with a 20A controller.
Morgan and company at cycle9.com carry some of the same NiCd and Li-Mn packs carried by Justin at ebikes.ca They also have some new 36V and 48V 15Ah LiFePO battery packs that look very interesting. There has been a recent scare for Lithium battery pack suppliers having to do with federal shipping regulations for lithium batteries where the potential for and heavy fines for improper paperwork and/or procedures. I noticed on the cycle9.com site that "Due to shipping regulations, at this time lithium batteries can only be shipped with a motor kit. We are working to address this situation in the near future." I hope this gets resolved soon for the sake of all Lithium battery suppliers.
Finally, I would like to mention Lithium-Cobalt batteries. These are sometimes just called Lithium-Ion batteries although the nomenclature is not that specific. This is the same chemistry that cought fire on occasion in Sony laptops. There are some brave experimenters here at Endless-Sphere that use this battery chemistry. At least one has had them catch fire. This chemistry is not for the faint of heart and I would suggest that you avoid it. It has more capacity per unit weight and volume than Li-Mn and LiFePO but are not as safe. Battery sellers are usually quick to point out that their batteries are either Li-Mn or LiFePO rater than generic Lithium-Ion to emphasize the safety of their chemistry.
Joey
