# Two vs one motor



## Ziggythewiz (May 16, 2010)

It depends how you hook things up. Two motors in series will use half the voltage, so you end up with the same power as 1. Two motors in parallel will use the same voltage and double the amps, so you get double the power and put double the strain on the battey. The efficiency will be about the same either way.

What kind of vehicle is this? e-bike or small 3 wheeler?


----------



## fhansson (Jan 31, 2013)

Ziggythewiz said:


> It depends how you hook things up. Two motors in series will use half the voltage, so you end up with the same power as 1. Two motors in parallel will use the same voltage and double the amps, so you get double the power and put double the strain on the battey. The efficiency will be about the same either way.
> 
> What kind of vehicle is this? e-bike or small 3 wheeler?


Ok, thank you for the reply. So parallell wiring would give me 500W and make it go faster. But what about battery life with serie vs parallel in same speed? I am probably going to limit the speed to 20 km/h and it takes a certain amount of energy but is it more efficient with two motors and more power?

It is actually a combination of a 3-wheel bike and skateboard. Kind of special made.


----------



## Ziggythewiz (May 16, 2010)

Battery life will be about the same to do the same thing whether done in parallel or series. Higher voltage allows higher top speeds and faster acceleration than using the same motor at half it's rated voltage.

Two motors may be less efficient because there's twice as many sources of inefficiency.


----------



## fhansson (Jan 31, 2013)

Ok, I understand. But what about torque? If one 250W motor is rated 2500 rpm and 24V/10A then two motors at same voltage must take 20A and 500W but is it still 2500 rpm or will it increase to?

If you connect two motors in parallel at half voltage 12V/10A will the result be half speed but same torque?

The reason I am asking is that one motor rated at 2500 rpm will probably make it go 40-50 km/h in full speed and that is way too fast. My idea was to lower the speed but keep the torque without using drivechain and gears.


----------



## Ziggythewiz (May 16, 2010)

fhansson said:


> Ok, I understand. But what about torque? If one 250W motor is rated 2500 rpm and 24V/10A then two motors at same voltage must take 20A and 500W but is it still 2500 rpm or will it increase to?


Yes the RPM of each would be the same, but you'd double the torque by combining them.



fhansson said:


> If you connect two motors in parallel at half voltage 12V/10A will the result be half speed but same torque?


Yes



fhansson said:


> The reason I am asking is that one motor rated at 2500 rpm will probably make it go 40-50 km/h in full speed and that is way too fast. My idea was to lower the speed but keep the torque without using drivechain and gears.


How do you plan to drive the wheels if not through a chain and gears?


----------



## fhansson (Jan 31, 2013)

Ziggythewiz said:


> How do you plan to drive the wheels if not through a chain and gears?


I'll put the wheels directly on the shaft. It's a special build I am testing out.

Thank's for your answers!


----------



## Ziggythewiz (May 16, 2010)

Very few motors can handle direct drive with no gearing. The only ones I'm aware of are those little play motors if you only stick a peice of paper on them.

I assume you're driving the skateboard wheels? I think you'll end up with a reverse dremel.


----------



## fhansson (Jan 31, 2013)

That's why I need high torque and low rpm. Maybe a BLDC is required, I am looking at it also but it will cost more and increase complexity of the build. Best would be a BLDC with Lithium battery but that will cost a lot.

It's not skateboard wheels. The rims are a lot bigger with rubber tires so there will be grip enough. There is no chance I can fit a 250W motor on the same shaft as skateboard wheels anyway.


----------

