Hi,

I think it might be easier -for me at least-

to have a thread where I can point you to,

to explain the basic math behind motors, power ratings,

and the magic of finding the ideal motor for your task

Within this thread I'll be using strictly metric values

namely kilogram (kg), meter (m) and sometimes kilometers per hour (km/h).

In case you want to convert:

Also you want to make sure you know the difference between

Power -Watt (W)- and Force -Newton (N)-

First of all, to have some clarification;

there's a minimum of TWO different power ratings for each motor.

Do not mix those two up.

The electrical Power is the amount of power a motor draws from your batteries,

where as the mechanical Power is the amount of power

you can pick up at the motorshaft to turn your wheels.

It's about the motor efficiency,

which for modern motors is above 80% in their recommended powerband,

the speed(rpm) and load at which you can run it until your batteries are drained.

If you do not know it's efficiency rating,

you should assume an efficiency of said 80% for a calculation,

although it's most likely better than that.

That way your motor will either have a tiny bit more power,

or it'll draw a tiny bit less from the batteries than expected...

Both

So whenever possible, choose a motor that is specifically made for electric vehicles

(EV motors) those are -to my knowledge- always rated in mechanical power, and they always rate the constant power

(some list the peak too, some don't)

If that is impossible for some reason, be sure to know it's continuous power if you need to calculate!

'sid

I think it might be easier -for me at least-

to have a thread where I can point you to,

to explain the basic math behind motors, power ratings,

and the magic of finding the ideal motor for your task

Within this thread I'll be using strictly metric values

namely kilogram (kg), meter (m) and sometimes kilometers per hour (km/h).

In case you want to convert:

10 lb = 4.536 kg

10 ft = 3.048 m

10 mph = 16.094 km/h

and

10 mph = 4.47 m/s

10 ft = 3.048 m

10 mph = 16.094 km/h

and

10 mph = 4.47 m/s

Also you want to make sure you know the difference between

Power -Watt (W)- and Force -Newton (N)-

**What kind of motor to choose?**

First of all, to have some clarification;

there's a minimum of TWO different power ratings for each motor.

**Pm [ mechanical Power, W ]**and**Pe [ electrical Power, W ]**Do not mix those two up.

The electrical Power is the amount of power a motor draws from your batteries,

where as the mechanical Power is the amount of power

you can pick up at the motorshaft to turn your wheels.

*that*is the number you want to know.It's about the motor efficiency,

which for modern motors is above 80% in their recommended powerband,

the speed(rpm) and load at which you can run it until your batteries are drained.

If you do not know it's efficiency rating,

you should assume an efficiency of said 80% for a calculation,

although it's most likely better than that.

That way your motor will either have a tiny bit more power,

or it'll draw a tiny bit less from the batteries than expected...

Both

*mistakes*are not really an issue for us**Math:****Pm = 0.8 * Pe**

**Attention:**All motors have a limit, and the closer you get to that, the worse will be it's efficiency.

Some companies

that's an amount that will kill your motor when applied for too long.

Whatever too long means; can be as little as just 10 seconds.

And it's best efficiency rating (at a very different speed and load).

That's fairly common for RC motors for example.

At it's peak power the efficiency of nearly every motor is worse than 50%

That means at least half the power applied is converted to heat.

You don't want that!

Some companies

*cheat*and tell you the peak powerthat's an amount that will kill your motor when applied for too long.

Whatever too long means; can be as little as just 10 seconds.

And it's best efficiency rating (at a very different speed and load).

That's fairly common for RC motors for example.

At it's peak power the efficiency of nearly every motor is worse than 50%

That means at least half the power applied is converted to heat.

You don't want that!

So whenever possible, choose a motor that is specifically made for electric vehicles

(EV motors) those are -to my knowledge- always rated in mechanical power, and they always rate the constant power

(some list the peak too, some don't)

If that is impossible for some reason, be sure to know it's continuous power if you need to calculate!

**If you do not need to calculate, this thread will be of no interest to you**'sid

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