# AC motor exhaust for heating?



## charliehorse55 (Sep 23, 2011)

I wouldn't think there would be any smell, but I don't think it would work very well. AC motors are very efficient, and the small amount of waste heat would not be enough to heat cold air from the environment. 

If you could manage to recirculate air from the cabin through the motor, it might be enough to keep the car warm.


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## dougingraham (Jul 26, 2011)

Red Neck said:


> Has anyone tried using an electric motor air cooling exhaust for hearing by connecting it to the cabin? So forced heated air heating of the cabin?
> 
> What are the temperatures one can expect to come from the exhaust?
> Is there a smell to it? In general, has anyone tried it?


The temperature gradient is wrong. If the air coming out of the motor is hot enough to heat the cabin then the motor is horribly overheated. Also there isn't enough waste heat except for when you are accelerating hard. If the motor is 90% efficient at your cruise speed that means 10% waste. Lets say you need 200wh/mile and you are going 60 mph. This means your cruise power is 12000 watts and if your motor is 90% efficient then you are getting 1200 watts of waste heat. From what I have read this might be enough if the temperature is in the upper 40's or low 50's. But if you had a heat pump you could use this to warm the evaporator and gain some advantage. Heat pumps work poorly when it is too cold. In all probability your waste heat at cruise will be higher than this making (300wh/mile and 85% efficiency = 2700 watts).

Once you run them for a while there should be no smell. If you are overheating them you would smell the lacquer out gassing before it fails. On a DC motor it is possible you could smell the brush dust but normally no smell.

It would require some good engineering to take advantage of this. If the output air is warm enough to take direct advantage of then you have a problem.


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## Red Neck (Feb 1, 2013)

I did it and it helps. On cold days, it keeps the cabin quite cozy after about a 7 minute drive. So on longer commutes, I don't need to use the electric heater anymore. But the motor needs to draw about 100 amps or more, to have an effect (72v nominal system)..


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## dougingraham (Jul 26, 2011)

Red Neck said:


> I did it and it helps. On cold days, it keeps the cabin quite cozy after about a 7 minute drive. So on longer commutes, I don't need to use the electric heater anymore. But the motor needs to draw about 100 amps or more, to have an effect (72v nominal system)..


What kinds of temps are you talking about? And is this 100 battery amps you are talking about or motor amps? If battery amps you are talking about waste heat levels of about half a hair dryer before you feel it. This is not going to warm up 0F degree air very much at all.


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## mizlplix (May 1, 2011)

My AC motor runs between 75C and 110C depending on the stop and go intervals. If I needed a heater, I would certainly place an outer jacket around the motor to collect cabin heat. 

The motor heat difference summer to winter seems to vary only maybe 10 C.

(That is just my present situation)

My old AC50 never got much over 60C.

Miz


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## Red Neck (Feb 1, 2013)

Motor amps. The temperature of the exhaust is between 50 and 70C on average. It makes enough of a difference for me to not need to turn
on the electric heater on drives longer than 10 minutes, but it gets
colder when standing still or on descents, of course.

As long as the motor is driven, it is effective. Why waste heated air, when it comes in so handy in winter?


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## onegreenev (May 18, 2012)

If your running a DC motor and want to collect the heat put a filter in line that can filter very fine dust. Brush dust is not what you want inside your vehicle and ozone alert. Not what you want in your beastie.

Pete


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## Red Neck (Feb 1, 2013)

It is an AC motor. I wouldn't use it on a DC motor. That dust is probably worse than soot...  I'm quite happy with the contribution it makes during driving and even during very cold days, when combined with electric heater, the cabin is warm, instead of only less cold, as was the case with the electric heater alone.


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## Tesseract (Sep 27, 2008)

onegreenev said:


> If your running a DC motor and want to collect the heat put a filter in line that can filter very fine dust. Brush dust is not what you want inside your vehicle and ozone alert. ...


The ozone I would worry about, but not the brush dust. Brushes can easily last 8-10k hours, so not much dust will be thrown off them on a per-hour basis.


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