# how hot should motor and controller be?



## piotrsko (Dec 9, 2007)

my rule of thumb: if I can't touch it, it is too hot to be happy.

get a hold of a non contact thermometer and see what the highest temps are, but since you say it thermal shut down, I'm guessing something is amiss.


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## Greenflight (Sep 13, 2007)

Make sure you're winding the motor out to its full potential. If you're running in too high of a gear that can cause the motor to overheat. This is easy to do, especially uphill.

And yeah, I would say if it's too hot to touch it's too hot.


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## Guest (Feb 23, 2009)

subevo said:


> my D&D motor after only 4 miles of mostly uphill driving is too hot to touch.is this normal? the controller is also very hot and the car cuts out and i have to wait 5minutes before i can go again.its ok going to work as its mostly downhill its a sepex motor . the supplied f1 and f2 cables are much smaller than the a1 and a2 cables .it was supplied like this. does this matter.just wondering how hot other peoples motors get.



Too hot can be before you can't touch it. The small motor will heat up fast because it is of low mass but for sure keep the rpm's up and keep them up while cruising. It is not an ICE and will do fine with running at high rpm's. If the motor does not have an internal cooling fan you need to provide plenty of cooling. If the controller does not have an added heat sink it needs one as well as a cooling fan. The smaller setups in cars really need that. 2/0 cable would be a good choice. What controller? Do you have a web site we can go to and have a look at your stuff? We love pictures. Lots of good ones. Please!

Pete : )

PS My Starter/Generator motor and controller heated up pretty darn fast too. It needs extra cooling and the Kelly Controller now has a heat sink.


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## CPLTECH (Sep 14, 2007)

EV motors like to run around 4K RPM for its internal cooling fan (attached to the shaft) to keep cool. Even household motors must run at design speed or they risk burnout. Keep the RPM’s high compared to the way one would drive an ICE. Feels weird at first.

A DIY EV conversion should always include a voltmeter and ammeter and as you drive keep a very close eye on them. Figure out what are the max continuous amps the motor can handle. My Advanced 9” in my S10 120V conversion has a continuous rating of 185A, 25HP. If exceeded more than 2-5 minutes, start to expect temp to rise. However, if I upgrade to a 144V system, those amps drop to 170 with a gain of 3HP. But if I downsize to 96V, the HP drops to 20 at 190A. Therefore, one must drive according to motor & battery voltage.

On a personal note, after driving over 6K miles in the past 2 yr and listening to driver comments here at DIY, I feel no one should consider anything less than 120V and a motor that is capable of at least 25HP continuous for the vast majority of vehicles. And even then, watch those elusive amps. Some, I am sure, will strongly disagree, but look at your experience with a small motor running at a less than optimal voltage for the performance you had expected. I will relent some and say that perhaps an 8” motor used in a lighter vehicle than mine is OK. But for the most part a larger motor does not consume that many more electrons to get the job done than a smaller one. Remember the days when a 6 cyl engine was considered economical? Often a small V-8 got better MPG because it was not under stress & strain as often.


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## Greenflight (Sep 13, 2007)

Yeah, that's why I use an external radiator fan ducted to the motor. My motor is a little lacking for torque at high RPMs so I try to keep it cool just in case.


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## Voltswagen (Nov 13, 2008)

Subevo
What model D&D motor do you have? 
What vehicle is it installed in?
What is the voltage of your system?


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## subevo (Aug 23, 2008)

its a 72 volt system.the car can be viewed at www.evalbum.com.do a search under location.united kingdom ,then scotland its a bright red daewoo matiz.the d&d motor details are listed there.ive added another fan to cool the motor and removed the controller mounting box front panel and its much better.i also cut an extra hole in the bumper and dont fully close the bonnet(hood) this has all made a big difference.thanks for all replys.


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## DavidDymaxion (Dec 1, 2008)

In a sepex motor, the field (f1 and f2) takes way less current than the armature (a1 and a2), so it is OK the wires are smaller, and is not related to your heating issue.


subevo said:


> ... its a sepex motor . the supplied f1 and f2 cables are much smaller than the a1 and a2 cables .it was supplied like this. does this matter. ...


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## Guest (Feb 27, 2009)

DavidDymaxion said:


> In a sepex motor, the field (f1 and f2) takes way less current than the armature (a1 and a2), so it is OK the wires are smaller, and is not related to your heating issue.


How much power is being feed into the field windings? Usually the field windings in a sep ex will take less power than the armature. Mine starts out with 24 volts and then down to 12 during field weakening. That is what it's set for. 

Pete : )


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## bblocher (Jul 30, 2008)

Just thought I'd through in my personal experience for reference. I added my own custom sensors to the motor and controller with a digital output for monitoring the temp. It is winter right now but the controller only goes up a couple of degrees F after a 30 minute drive at 65 mph. I added a large heat sink and fan though that I think is helping significantly. The motor has no special added cooling features other than the built in fan. It does go up to about 100F. So in short, the controller is still rather cold to the touch and the motor is barely warm. We'll see what happens come summer as it can get rather hot.


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## Tom Thomson (Jun 11, 2008)

subevo
My D&D motor has a thermocouple embedded in one of the brushes (the hottest part of the motor) and it will occasionally show 400F. The engineer at D&D says this is ok as long as I don't hold it there. If memory serves, the max continous case temp is 185C which is 376F. If you go to your local welding supply shop you can get "tempilsticks" which are crayons designed to melt at various specific temperatures. Mark the case with one of these, drive the car and see if the motor has exceeded that temp. 
Again from memory, my Alltrax controller is good for 95C at which point it shuts down.
tommyt


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## major (Apr 4, 2008)

Tom Thomson said:


> If memory serves, the max continous case temp is 185C which is 376F.


Hi Tom,

I'd check your memory. 185C is way too hot for the "case". I'm guessing you mean the outside of the frame of the motor. Most use class H insulated motors. Meaning 180C max for the insulation. In a ventilated motor, when the inside temperatures reach close to 180C, that outside frame temperature might be in the range of 90-110C.

100C is pretty hot. H20 boiling. So I see some guys complain that they can't lay their hand on the motor frame after long runs. 

Regards,

major


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## subevo (Aug 23, 2008)

i bought a cheap infrared thermometer.it reads after a run uphill 65 degrees centigrade at its hottest point on the casing.this may be just ok.


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