Since I plan on using a 120 kW peak motor, which will probably be running an average of 35 kW throughout the course of a 15 minute race, 9 kWh would no doubt see a throttle-happy punter like me through. So with 7-10 kWh on board as a goal, and a 360 V nominal system (seems to be what the Rhineheart motor controllers are OK with) let's see what can be arranged.
360 V means 110 LiFePO4 cells in series, or 90 LiPo cells in series.
The only LiFePO4 worth using is A123's 20 Ah cells. A 1p110S arrangement would mean a 7.2 kWh pack capable of a maximum of ~500 A discharge. It would also weigh just 55 kg. So while I might be running out of juice on the last lap, I would have got there a bit quicker since the bike would have been pretty light. This would cost about $8.5k from Mavizen, or considerably less from Cell_Man.
LiPo gives a few more options. Using some of those Haiyin 6 Ah cells, I would need 90 in series. A 5p90s arrangement would give me my 10 kWh capable of a stupendous discharge rate. They are small format, so I can fit these into a Gixxer frame with a bit of clever planning and I'd be close to 77 kg worth of cells. At $13,000 that is just way too much money.
Turnigy cells work out much cheaper, and a 5p90s arrangement with these guys would make for a 8.3 kWh pack, weigh only 59 kg and cost about ~$6k after delivery. These cells would need some fancy arrangements too. Alternatively I can try to fit 6p90s, and have a 10 kWh pack weighing just over 70 kg, and cost about $7k.
OK, is there a problem with running a 1p110S arrangement? I'm expecting to be pulling ~500 A on occasion, which is 25C. If one of my cells is not up to the task, I have a whole system failure. A123 cells are pretty darn awesome; safe, easy to balance and monitor with a BMS, but would I be asking too much of smaller pack?
Are these Haiyin cells made from Unobtainium or is there a reason why they are so damn expensive?
Can I trust Turnigy cells to not fail/explode?