Re Batteries and this article
http://www.electricbike.com/li-nmc-o2-the-next-best-battery/

I'm not sure I quite agree with the history. ISTM we had in sequence
- LiCo
- LiCo Poly
- LiMn
- LiFePo
- LiNiCoMn

For about 18 months now, BMSBattery/GreenBikeKit have stopped selling LiMn and sell either LiFePo or LiNiCoMn which all seem to be sourced from ECityPower.

LiMn was by far the most common chemistry in cheap (and expensive!) built up electric bikes for a long time. It's a cheap, light, safe chemistry. The problem is low C, but much more importantly short life. And not just a short number of cycles but a short shelf life as well. Losing 20% capacity a year even if you don't use the battery much leads to a lot of expense and warranty claims. LiNiCoMn has the same low cycle life, light and cheap characteristics, but it seems to have a longer shelf life and a slightly higher C.

LiFePo is 30 to 50% heavier and 10-20% more expensive than LiMn/LiNiCoMn. It's safe but mainly, it's got at least double the cycle life of LiMn/LiNiCoMn and seems to have an almost indefinite shelf life.

C values seem to be as much about cell packaging as chemistry for LiFePo/LiMn/LiNiCoMn Pouch and prismatic cells with high AHr per cell tend to have a C value of about 1 to 1.5. So cheap packs both cased and shrink wrapped or from suppliers like Ping seem to be like this. Cylindrical cells from A123 or Headway tend to have C values of 3C to 5C upwards. And for a fully built pack, C is as much about cells in parallel as anything. eg 10s2p having twice the C of 10s1p Again BMSBattery/GreenBikeKit are now selling LiFePo Headway based packs with a BMS and with C values of 3C to 5C and either cased or shrinkwrap.

RC packs may be fine for enthusiasts that know what they're doing, but even telling others about them scares me! FIRE! And secondly, they typically don't have any BMS so don't have any inherent protection from over-under voltage or balancing. FIRE!

Unless you've got a specific design need, it feels to me like the two best value at the moment for a typical E-Bike build are 36v15Ahr and 48v10Ahr. With the choice being LiNiCoMn for smaller/lighter/cheaper or LiFePo for lifespan/higher-C but a bit more heavy/bulky/expensive.

http://www.bmsbattery.com
http://www.greenbikekit.com/