is it needed to use a resistor in a circuit consisting of a 12 volt motor and a 12volt rechargable battery .

i' making a wheel chair run by a 12 volt rechargable  battery connected to a 12volt motor and also a switch.Is a resistor needed,if needed what resistor should be used?Can I use a variable resistor

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You do not need a resistor to run the motor, however controlling the speed of the motor depends on the type of motor and gearing some motors speed is controlled by frequency others are controlled by current like in this circuit.
Motor Regulator.bmp
A Vbe multiplier in a novel circuit. Nice.
I use it on PC fans works great and if you want it to change speed by its self use a thermistor.
It's going to need a big transistor to run 2 100 + watt motors to drive a wheelchair.
Mosfets or transistors and combine the circuit with this circuit. that for the original driver and this to multiply the power.
78xx Current Regulating.bmp
A linear regulator on a wide range, high power motor is going to waste an enormous amount of energy.
All variable speed controls for motors waste energy.
That's not true: PWM doesn't, or only trivial amounts. I have a 300Watt drive for work project which is 7cm long, 4cm wide and 1cm thick. On worst case (full current, half speed, its barely warm.
Both circuits have their advantages PWM (Pulse Width Modulator) is very efficient and they will drive brushless motors, they do vibrate with some motors and gearing but you can buy them cheap enough. However when you consider the author of this question and they just wanted to know if you needed a resistor to connect a 12 volt motor to a 12 volt battery? A PWM might be the best way for them to go.
If you get vibration, odds-on you don't have enough inductance in the motor.
rickharris3 years ago
No - BUT to run your motor your battery MUST be able to supply the required current for the motor.

No you can't control the speed directly with a variable resistor. You need to research Pulse Width modulation PWM speed control.