These Snow Days are the Days I love My Car......

[Kim-n-Dean]

Altitude effects everything in different ways, cars, humans electric motors...anything that demands POWER is directly effected.

I'm curious as to how altitude affects electric motors. While I've never dyno'd my nitro or electric R/C cars at 11,000' when we are camping, I can see a lose in power on the nitro cars, but never on the electrics. I would think an electric car would be faster at altitude. No power lose, but the air is thinner. Therefore, less aerodynamic drag.

[Grim2.0]

I'm curious as to how altitude affects electric motors. While I've never dyno'd my nitro or electric R/C cars at 11,000' when we are camping, I can see a lose in power on the nitro cars, but never on the electrics. I would think an electric car would be faster at altitude. No power lose, but the air is thinner. Therefore, less aerodynamic drag.

I'm curious as to how altitude affects electric motors. While I've never dyno'd my nitro or electric R/C cars at 11,000' when we are camping, I can see a lose in power on the nitro cars, but never on the electrics. I would think an electric car would be faster at altitude. No power lose, but the air is thinner. Therefore, less aerodynamic drag.

Ironically enough Electric Motors are my specialty!!

The nitty gritty is in fact air density which effects ambient temperature, the thinner the air the less the cooling capacity, electric motors MUST have a set amount of cool air blowing over them to push the heat dissipating on the cooling fins of the body. The hotter a motor gets the less performance it has, the solution is oversize and de-rate to account for the power loss. The principal per EASA is a 3% de-rate per 1,000ft after 3,300ft ASL (above sea level).

Those little RC cars dont have much power in them for you to even notice that 3% loss per 1000FT even if you have a 1hp operating at 6,000ft with a 9% loss you would have roughly .93HP not nearly enough to visually notice. The other thing you have to factor is you live in Colorado and in Parker along where I live we are already above 3300ft ASL you already have losses that you are accustom to and dont even know it. The motors i deal with range from 100HP to 500,000HP so the de-rate and loss is very significant.

I actually just had two 450HP motors at Cripple Creek gold mine in Victor Colorado overheat and fail three weeks ago because the original engineer did not account for altitude, the demand on the machine they were running was 450HP but because they only gave them a motor capable of 450HP at the 10,000 ft ASL they were at (21% de-rate) the motor was actually only operating at 355HP thus the demand was forcing the motor to work harder to keep up, the motor will do what is asked of it so it works harder, hotter until something either goes boom or burns up.

Result I sold them two 600HP motors operating at 474HP @ 10000ft ASL. Good day for me bad day for them

[Kim-n-Dean]

Ironically enough Electric Motors are my specialty!!

The nitty gritty is in fact air density which effects ambient temperature, the thinner the air the less the cooling capacity, electric motors MUST have a set amount of cool air blowing over them to push the heat dissipating on the cooling fins of the body. The hotter a motor gets the less performance it has, the solution is oversize and de-rate to account for the power loss. The principal per EASA is a 3% de-rate per 1,000ft after 3,300ft ASL (above sea level).

Those little RC cars dont have much power in them for you to even notice that 3% loss per 1000FT even if you have a 1hp operating at 6,000ft with a 9% loss you would have roughly .93HP not nearly enough to visually notice. The other thing you have to factor is you live in Colorado and in Parker along where I live we are already above 3300ft ASL you already have losses that you are accustom to and dont even know it. The motors i deal with range from 100HP to 500,000HP so the de-rate and loss is very significant.

I actually just had two 450HP motors at Cripple Creek gold mine in Victor Colorado overheat and fail three weeks ago because the original engineer did not account for altitude, the demand on the machine they were running was 450HP but because they only gave them a motor capable of 450HP at the 10,000 ft ASL they were at (21% de-rate) the motor was actually only operating at 355HP thus the demand was forcing the motor to work harder to keep up, the motor will do what is asked of it so it works harder, hotter until something either goes boom or burns up.

Result I sold them two 600HP motors operating at 474HP @ 10000ft ASL. Good day for me bad day for them

I had no idea. That's some cool info. My motors have fans on them for cooling. If the fan has enough CFM to cool the motor as if it were at sea level, would the altitude affect still be there? I'm assuming the altitude affect only happens after the motor heats up?

[Grim2.0]

I had no idea. That's some cool info. My motors have fans on them for cooling. If the fan has enough CFM to cool the motor as if it were at sea level, would the altitude affect still be there? I'm assuming the altitude affect only happens after the motor heats up?

Indeed it would and correct but keep in mind these motors get hot fast, there is low voltage but high current flowing through them and the harder the motor works the higher the current. On an RC car every time you stop you have to start again and starting or ramp up is the peak of the torque curve demanding higher current. The motors i work with are the same as your little motor, it has a TEFC enclosure (totally enclosed fan cooled). the CFM rating on the motor is set per that HP and speed rating however all electric motors have a standard insulation class and ambient temp rating, the higher the DE-rate the less the motor has to work thus less heat generated.

Regardless of the amount CFM flow over your motor you still have to account for Watts Loss through heat in the motor the motor will always generate the same amount of heat based on the function its performing and you will always supply the same amount of cooling air based on rotational speed, as long as you do not exceed the ambient rating no harm no foul. The biggest argument we have is "bigger fan more cooling air" which is wrong, you can gain the same amount of CFM with a fan half the size of a 10" DIA fan based on rotational speed. Its all about speed, and the fastest motor on the market that is coil wound and not a permanent magnet stator or rotor is 3600RPM or 2-pole, usually used for reciprocating Compressors.

Your RC cars have an advantage though....its a moving part, you have the cooling air from your fan on the motor but also the air over the vehicle when in operation.


Edit: One option there is to eleviate this issue is a Water cooled Motor however this is not cheap my any means and is much larger as well. Even still there will be slight losses due to atmospheric pressure and the motor having to work harder.

[Kim-n-Dean]

Indeed it would and correct but keep in mind these motors get hot fast, there is low voltage but high current flowing through them and the harder the motor works the higher the current. On an RC car every time you stop you have to start again and starting or ramp up is the peak of the torque curve demanding higher current.

It's pretty amazing the current these little suckers are capable of! My 6400 mAh LiPo batteries, brushless 2400Kv motor and ESC can pull over 160 amps.

[Grim2.0]

It's pretty amazing the current these little suckers are capable of! My 6400 mAh LiPo batteries, brushless 2400Kv motor and ESC can pull over 160 amps.

160Amp @ 2400Kv is pretty impressive, and will tickle if you touch it as well, I imagine there are quite a few capacitors in there, and this is all DC power we work with a ton of AC power but we also sell Variable frequency drives so the AC from the utility comes in, is converted to Dc through IGBT's then back to AC to the Motor.

The Lower the voltage the higher the current draw, always makes me laugh when someone brags about voltage being high IE 100,000 volts but its only drawing 1.2 Amps enough to sting but not put you down.

Then i have a 230V motor that can pull 7,250 amps that will not only kill you but will cook, and blow your ass up.


SCIENCE!!!

[Kim-n-Dean]

The Lower the voltage the higher the current draw, always makes me laugh when someone brags about voltage being high IE 100,000 volts but its only drawing 1.2 Amps enough to sting but not put you down.

What makes me laugh is when I hear someone say they are going to swap out all their 110V equipment for more expensive 220V because they think their power bill will go down. I hear it all the time for grow room lights. A 1,000W light still pulls 1,000 watts regardless of input voltage. Since the power company charges by watt/hour, your bill remains the same! Dropping amperage on the line doesn't help your bill.

[madvlad]

Ironically enough Electric Motors are my specialty!!

The nitty gritty is in fact air density which effects ambient temperature, the thinner the air the less the cooling capacity, electric motors MUST have a set amount of cool air blowing over them to push the heat dissipating on the cooling fins of the body. The hotter a motor gets the less performance it has, the solution is oversize and de-rate to account for the power loss. The principal per EASA is a 3% de-rate per 1,000ft after 3,300ft ASL (above sea level).

Those little RC cars dont have much power in them for you to even notice that 3% loss per 1000FT even if you have a 1hp operating at 6,000ft with a 9% loss you would have roughly .93HP not nearly enough to visually notice. The other thing you have to factor is you live in Colorado and in Parker along where I live we are already above 3300ft ASL you already have losses that you are accustom to and dont even know it. The motors i deal with range from 100HP to 500,000HP so the de-rate and loss is very significant.

I actually just had two 450HP motors at Cripple Creek gold mine in Victor Colorado overheat and fail three weeks ago because the original engineer did not account for altitude, the demand on the machine they were running was 450HP but because they only gave them a motor capable of 450HP at the 10,000 ft ASL they were at (21% de-rate) the motor was actually only operating at 355HP thus the demand was forcing the motor to work harder to keep up, the motor will do what is asked of it so it works harder, hotter until something either goes boom or burns up.

Result I sold them two 600HP motors operating at 474HP @ 10000ft ASL. Good day for me bad day for them