I have brush DC motors using which I am making an RC car. The motors are rated "3V 16500 rpm". Will I damage my motors if I use a voltage above that ??
How much above? 3.5v would be OK, 5v is excessive.
Weedpharma
If you use PWM to control the energy going into the motor you could safely use higher voltages - provided you keep the PWM duty cycle below the level that is equivalent to the energy flowing at 3 volts.
For example a PWM duty cycle of 50% with 6v would be about the same as 100% at 3v.
Motors are damaged by heat (due to excessive average current) rather than by voltage (assuming you are not considering 100s of volts that would breach the insulation).
...R
So if I use an H-Bridge with VCC at 3.3V from the Arduino and write a 255 value from a PWM pin and another to GND can I successfully run the motors safely?
SagarDev:
So if I use an H-Bridge with VCC at 3.3V from the Arduino and write a 255 value from a PWM pin and another to GND can I successfully run the motors safely?
That should be fine. But you may find there is a voltage loss in the h-bridge so that 3.3v input may not provide 3v at the motor.
...R
L293 and L298 H-bridges loss 2V or so, so you'd have to run those from 5V for this motor really!
Over-voltage will work, but the motor's life will be reduced - small cheap DC motors wear out quite
quickly anyway. Gross over-voltage will burn out the motor though.
I am making an RC car which has 2 H-Bridges connected to VCC as 5v and GND to GND from my Arduino Mega ADK. I am powering my Arduino from a power bank through the programming port which is rated as 5V 1A. I have the same motors which I mentioned in Quote #1. I have connected pins 12,11,10,9 as the variable input to the H-Bridges. Do I have sufficient power to run all 4 motors at 16500 rpm??
Why doesn't anyone reply?????
Probably because there is no simple answer to your question.
Have you tried it? What happened?
In general more amps are better. Extra amps won't cause any harm.
...R
Hi,
16,500rpm, you will not get that rpm out of that motor when you put a tyre on it and put it on a surface to run.
I don't know how heavy your RC car is, but those little motors do not have a lot of shaft torque.
Can you post a picture of your RC car please?
Tom.... 
I am still planning to make it and the estimated weight is around 300 grams
Without knowing the winding resistance or stall current of the motor there's no way to judge what current is needed