Electric Bike

[ElectricMan27]

Hello i am looking to build a electric bike/motorbike if i were to use a power source of numerous deep charge batteries that total voltage would be 46V. And a 36V or 24V motor what sort of Variable resistor would i need to control the speed? Would i use a control board to control the motors, power and speed? If so what model or type would be best and where would i get it? How would i connect the batteries together?
As you can tell i'm full of questions because my knowledge is limited but any help and input is gratefully appreciated

 

[BobK]

You will need a motor speed controller board rated for the voltage and current used by the motor. Take into account that the stall current is much higher than the running current, and the speed controller must handle the higher stall current.

You can find these at very reasonable prices (read as ridiculously low) on Ebay.

Bob

 

[Gryd3]

Hello i am looking to build a electric bike/motorbike if i were to use a power source of numerous deep charge batteries that total voltage would be 46V. And a 36V or 24V motor what sort of Variable resistor would i need to control the speed? Would i use a control board to control the motors, power and speed? If so what model or type would be best and where would i get it? How would i connect the batteries together?
As you can tell i'm full of questions because my knowledge is limited but any help and input is gratefully appreciated

BobK Is right on the nose...
Using a simple Variable Resistor will waste a lot of power... They work by simply adjusting the resistance in-line with the motor... the amount of power wasted can be HUGE! So you typically need a very large/expensive part for this. Think... at half speed, 18 - 23V will drop across the resistor, and if the motor pulls 3Amps, this part will get hotter than an incandescent light-bulb! (60+ Watts ... in this example. Real-world will be based on the actual draw of the motor)
The parts Bob mention are active components that usually operate in with PWM, and run incredibly cool and efficient. They also have more features. You can find controllers that offer 'speed' control instead of simple voltage adjustment, as well as things like over-current protection to prevent you from burning out your motor if the motor stalls. (Usually at a higher price, but worth it!)

 

[Bluejets]

Affordable controls available from here........
http://oatleyelectronics.com//index.php?cPath=94&osCsid=be6f53c072fb6637b58be390a4ff4679

 

[ElectricMan27]

Thank you everyone for your replies i was wondering if you could give me some links or details on appropriate speed controllers

 

[Gryd3]

Thank you everyone for your replies i was wondering if you could give me some links or details on appropriate speed controllers

Well... there are tons of links, but google will show you that
Consider two types of controllers to begin with:
- Linear or Analogue
- PWM

In the simplest form, you can use a rheostat or something like the fan control in a car... (Multi-position switch to a selection of high power resistors.)
This method wastes a lot of heat, and is inefficient.

The digital control uses PWM or an alternative switching technology and is much more stable and efficient.

In any case.... the controller MUST be sized based on the needs of your motor.

 

[Bluejets]

I thought I did...?

 

[ElectricMan27]

Could i give the controller more power than the motor needs and will it hold it back or will it fry the motors

 

[ElectricMan27]

Say 48v to a 36v controller

 

[Gryd3]

Could i give the controller more power than the motor needs and will it hold it back or will it fry the motors

Say 48v to a 36v controller

Depends entirely on the controller.
If it has current / voltage sensing on the output then yes... otherwise it's a pretty stupid device that will typically just pass the full voltage to the motor if you crank the speed up.

 

[ElectricMan27]

what do you think would be better for a motor 36v or 48v?

 

[BobK]

Match the voltage to the rating of the motor.

Bob

 

[ElectricMan27]

If i used 48v for a 36v motor would the controller have power for longer than 36v to 36v

 

[ElectricMan27]

Geared Motor or straight???

 

[Alec_t]

If i used 48v for a 36v motor

... you may well damage the motor .

 

[Gryd3]

If i used 48v for a 36v motor would the controller have power for longer than 36v to 36v

Based on the understanding you have of the subject thus far, I would strongly urge you against using a higher voltage for the motor than it's rating. Most motor controllers aren't very complicated, so using a 48V supply and a 36V motor would most likely end up in the controller sending 48V to the motor. This 48V may be pulsed, or in the form of PWM, but unless you understand the workings, it's a bad idea to even try.

Geared Motor or straight???

This is your preference and is highly dependant on the motor you plan to use. If your motor has low torque and high RPM, you will want it geared. Alternatively, if your motor is very high torque and low RPM then you may want this geared as well depending on the speeds you want to achieve.

 

[m3vuv]

ive been building ebikes for about 5yrs,if it was me forget lead acid batterys for a start!,if you use a brushless direct drive hub motor expect to get about 1kmh per volt,i run a homemade 13s 17ah lithium ion pack running a 500 watt controller thru a 40a smart bms,the hub motor was for a 24 inch wheel,i built it into a 27.5 inch rim,it will do 40mph flat out fully charged and has a nange of about 20 miles if i dont pedal,avoid a bms company called MGOD they screwed me over!,also avoid geared motors if you plan on running more than 250 watt,mine lasted about 50 miles runnng 750 watts untill it stripped the gear teeth.

 

[Harald Kapp]

@m3vuv : Please check the age of a thread before replying. This one is from 2016 and hasn't been replied to since. Most likely no ne is interested in such an old thread anymore.
Thread closed.