If simplicity is important, you can probably do without a motor controller altogether, and just use relays or transistors to switch the motor current. You won't have speed control, so you'll have to choose motors that run at reasonable speeds on the voltages you have.Could I get more info on this please?
I don't really understand how motors are controlled in r/c cars or robotics.
If you just hook a motor up to a battery, without any motor controller in between, the motor will rotate at a speed that depends on the load its turning, and it will draw a current that depends on its speed. If you're ok with this, then you might be able to get away without a motor controller. You'll be able to make the motor go or not go, by disconnecting it. You can make the motor go backwards by wiring it backwards. (Not all motors are reversible, but all the DC motors I've come across are.)
So, if you're ok with just stop, forward, and reverse (i.e., you don't need to vary the speed), then you might
be able to get away without a motor controller. All you do is choose a motor and battery voltage so the motor naturally runs at a speed you can live with. When the motor runs into tough going, its speed will decrease, and this speed decrease will cause the current it draws to increase, and the power that the motor delivers will increase as a result (up to a point).
This brings up one more important complication. As I said, the current a motor draws depends on its speed. Most motors will draw enough current to burn out their windings (melt insulation, cause a short circuit, and ruin the motor) if you increase their load sufficiently. If you hold a motor's shaft still, while it's trying to turn, for example, and the battery is capable of supplying enough voltage and current to burn out the motor windings, then you will get a ruined motor. This is because most motors have very low-resistance windings, and rely on motor speed to limit the current in their windings to a safe level. (Motors act as generators, while they are turning, and the voltage they generate opposes the applied voltage, so the windings only see the average difference
between the applied voltage and the generated voltage.)
You can avoid burning out a motor by ensuring that the motor never runs so slowly that it gets too hot, or you can use a weak enough battery that the motor won't burn out even if it stalls, or you can put a fuse or a circuit breaker in series with the motor, or you can get a motor with an internal temperature-based cut-off element.
Now, if you find you can, in fact, do without a motor controller, then you can put relays, or transistors, between the battery and the motor, and control the motor by controlling the relays or transistors.