I
think I found the manufacturer of Team GB's track cranks (not sure):
Track Cycling Instrumented Aero Cranks | bf1systems
These force measurement cranks were designed from the ground-up as cranks which were to be instrumented, and had to survive the highest loads seen anywhere in cycling, during the standing start of a velodrome race.
Each crank is capable of measuring the torque and force applied to it, along with its position, and transmits this wirelessly at 192Hz to the receiver mounted on the bike.
An internally mounted battery powers each crank, providing approximately 7 hours of continual use.
Status LEDs on the cranks provide the user with information on the current status of each crank arm.
7hrs doesn't seem like a lot, but because it broadcasts at such a high rate, that's probably why they battery doesn't last very long. But, this is in line with the theory that more data is better. I'd imagine that they are simply charged at the end of a training session like we'd charge a cell phone.
I wonder what head unit they used to record the data. Any ideas?