# Help me understand thermal load



## bart_dood (Sep 2, 2010)

Hi Folks,

I am building an EV based off using 2x Honda Insight IMA motors and two honda controllers.
The motors according to honda put out 13.3hp each, so about 27hp max for the two.

The issue I'm trying to get my head around is heat, someone mentioned to me they thought the motors would get too hot in continuous use, however normally honda has these things sandwiched between the tranny and the ICE. There is zero airflow to cool them.

I plan on adding some good forced air cooling which will flow all around the stators and through the rotors too.

I am trying to estimate if this will be enough. I know of course this all depends on duty cycles and speeds etc, I won't be driving on the highway much at all, at most a couple of miles where I'll stick to 55mph.

Any light someone could shed on this would really help.

Thanks


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## rillip3 (Jun 19, 2009)

At peak efficiency most electric motors are ~ 95% efficient, but you're rarely running at peak efficiency (you're more likely to be running closer to peak power than peak eff.). A ballpark assumption I've seen is ~ 80% for a varried duty load. So take your peak kw output, find 20% of it, and you'll have to dissipate that much energy as heat. Now figuring out how many kw of heat your forced air can dissipate is beyond my ken, but you may be able to find something with ratings on it to give you an idea.


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## Guest (Sep 27, 2010)

I'd almost bet that the person who said it would get to hot thinks that you will be driving it like an ICE for hours at a time. With decent cooling it should do just fine. Don't let nay sayers drag your project down. Just do your project and if it needs more cooling then figure out what it will need to satisfy that issue. Keep us in the loop even if it is a tough project. We'd all love to see how that works. Did you figure out a way to separate the motors from the ICE and couple them together? I'd love to see that too. What about mounting points? 

PHOTOS man PHOTOS

Pete


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## bart_dood (Sep 2, 2010)

gottdi said:


> I'd almost bet that the person who said it would get to hot thinks that you will be driving it like an ICE for hours at a time. With decent cooling it should do just fine. Don't let nay sayers drag your project down. Just do your project and if it needs more cooling then figure out what it will need to satisfy that issue. Keep us in the loop even if it is a tough project. We'd all love to see how that works. Did you figure out a way to separate the motors from the ICE and couple them together? I'd love to see that too. What about mounting points?
> 
> PHOTOS man PHOTOS
> 
> Pete


Thanks!

I just did a quick calc figuring out how much energy a warp8 at highway speeds loses as heat which comes out at 2300 watts for a certain speed. The same calc for my motor comes out at 1100 watts, half as much, also my motor is actually two motors so per motor this works out at 550 watts per motor.
I am embedding temp sensors in each motor and will have forced air cooling so this heat seems to be pretty managable considering its half what a warp8 is and people run those a lot etc under similar conditions.
I have photos on my blog, check it out!

I'm hoping to get some progress made this weekend, my son and wife are gone all weekend so more time to play...


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## Guest (Sep 27, 2010)

More photos. I did check out your blog. Nice that its going into a VW.  Can't wait for more. Might be just the ticket for others with VW conversions.


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## bart_dood (Sep 2, 2010)

bart_dood said:


> Thanks!
> 
> I just did a quick calc figuring out how much energy a warp8 at highway speeds loses as heat which comes out at 2300 watts for a certain speed. The same calc for my motor comes out at 1100 watts, half as much, also my motor is actually two motors so per motor this works out at 550 watts per motor.
> I am embedding temp sensors in each motor and will have forced air cooling so this heat seems to be pretty managable considering its half what a warp8 is and people run those a lot etc under similar conditions.
> ...


I'm looking at water cooling now, there is a space inside the housing between the stator and aluminum, I plan on wrapping 1/4 copper tubing around this with heat coupling gasket to transfer heat.
I'll bring the tubing out and pump ethyl glycol water mix through it using a PC water pump, they pump around 1 gpm.
I did some calcs on the temp rise today and it should be quite low, this will keep my motor running quite cool and allow me to pump more current through it, the extra power is a nice to have.
Can't decide if I should keep some air cooling as well....it adds extra complication but I'm not sure I'll need it or not...


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