What components exactly determine the speed?

[halfawake454]

So, I've kind of got an idea of this, but I'm tired of being confused about it. What components determine how fast said ebike will go?

What I've picked up thus far it seems is that generally, higher voltage batteries provide more speed and amp hours determine distance. The thing is, I have seen people showing bikes off and one with lower voltages have still gone faster than the bike with higher voltages. So, what is different? Does the size of the motor determine this difference?

I'm just kind of confused and curious on what exactly determines speed on an ebike.

If someone could explain this to me I'd appreciate it.

 

[vanilla ice]

Theres volts, amps, amp hours, and watt hours.. yea the hour stuff is about capacity. The motor and voltage play a big part in determining your max speed. Differnt motors will spin at different rpms with the same given voltage, then you've got gearing too if its a non-hub. Err even with a hub theres gearing changes by way of different size rims.

 

[dozentrio]

I think you might confuse the poor guy

I will say what I think is right, and if im' wrong perhaps people will correct me:

Higher voltage makes a motor spin faster. This is of no use, however, if the motor is too "weak" to actually push something at that speed. Imagine a teeny weeny hobby train motor or something. You can give it 48 volts and it would spin very fast, but it couldn't spin that fast if it were connected to your bike wheel. This is where current comes into play.

The torque developed by a motor depends on the current it draws. A "big" motor will draw more current at 12 volts than a "small" motor will. If you increase the voltage, they will both draw more current. If you increase the voltage enough, a motor will draw so much current that the windings will heat up and stuff will start to melt/fail.

Ugh, its too late, and I realize I don't know nearly enough about this to be posting.

 

[DerekG]

I think you did a fine job

Here are some main points to remember in bullet form

* Voltage determines max RPM's = max speed. For example, at 36 volts my bike spins at 26 mph, at 60 volts it spins at 39 mph.

*Current determines acceleration (torque translates to motion so more torque = faster feeling bike if your stopped at a light for example.)

*Current determines top speed a little bit... My motor at 36 volts spins at 26 but if riding I only get 21 because of air resistance. At 60 volts I only get 30 instead of 38-39. Let's pretend my controller is maxed out at 30mph. If I upgrade to bigger (more amps) controller at same voltage then I maybe get an extra mph or so.

*Wheel size determines speed. Assuming the motor is the same, as small wheel will provide more torque (acceleration) but less top speed than same motor in big wheel. To compensate for this, manufacturers of motors "wind" motors differently to get different RPM's at same voltage... This is where it gets confusing. I have a 9x7 9 Continents motor. Others have slower motors like 10X6 9 continents. More torque but lower top speed which is good for big wheels.

 

[halfawake454]

Just forget I ever asked, lol, nah I'm jk. Thanks for the help. At least my confusion was understandable, a lot of variables involved it seems.

 

[swbluto]

Just forget I ever asked, lol, nah I'm jk. Thanks for the help. At least my confusion was understandable, a lot of variables involved it seems.

It is kind of complicated from the n00b perspective, but higher voltage = more speed for any given motor. A lower winding motor will typically go faster (i.e., 404 is faster than 4012; 40 4 has 4 windings, 40 12 has 12 windings).

For a hub motor, you can change speed by changing the rim size. Usually bigger rims allows higher speeds, but this can be unintuitive. This is where a simulator can be helpful.

For a non-hub motor, you can change speed by changing the gearing. The changeable speed range is far greater for non-hub motors than hub motors(The difference between a 26" rim and 20" rim isn't much) and is one of the reasons why I like non-hub motors better (I've had both). They just seem more customizable to get it the way you want it without a bunch of extravagant cost.

If you look into any one of those categories, you can find there'll be nuances but that's the top-level gist of it.


If you want to know how your vehicle affects your speed, usually greater aerodynamics = greater speed. Less weight = greater speed on hills.

 

[dogman dan]

It is a confusing subject, and gets more confusing when comparing apples to oranges to grapefruit.

Apples would be direct drive hub motors with no gears, and comparisons should be made with similar size motors. The clyte 530x models are huge compared to most.

Oranges would be hub motors with internal gears, and are different from Direct drive motors in performance.

Grapefruit would be motors that drive a chain. Similar to geared hubmotors in that they use gearing, but the flavor is different. Chain drive is very very different from a direct drive hubmotor.


Once you seperate the motors by category and size, then comparisons of performance by changing voltage or amps will get a LOT less confusing. Too many variables is junk science.

 

[monster]

all components determin speed (controller, motor and batteries). the limiting factor is usually thet batteries tho as they are the most expensive part. it is very complicated tho. you have to do tests to find out whats limiting things.