I plan to build a DIY electric bicycle using a standard geared BLDC hub motor (36V and 250W rated, 500W peak). To get 36V rated battery, at least 10 Li-ION 18650 cells are to be connected in series (that's how it is usually done). In this case, the battery at maximum charge will give out 42V and will discharge gradually till 30V (limited by a BMS).
Assume that I need to build 9s2p battery. This means that the battery will operate in a voltage range between 37.8V - 27V. Assume that BMS and controller are all good with that.
What will happen to a motor if it's connected to such a battery (with lower voltage compared to 10s2p)? How the maximum speed, torque, efficiency and the lifespan of the motor will be affected? Will power output change or will it be compensated by the increased current?