I am trying to build a robot using a kit I got from amazon: https://www.amazon.co.uk/DFRobot-Tank-Mobile-Platform/dp/B014L1CF1K?th=1 (it uses plastic motors).
The main problem that I am having is that whenever I try to apply a battery with 9 volts to one of the motors it only moves the slightest amount. I am not sure if the voltage is too low or not because in the manual it is using 7.4 volts.
The motors are connected up to a motor driver, here is a diagram of what it looks like
Could the motors potentially be broken? (Hope not because it means I will have to dissect the whole robot)