# Curtis 1231c higher speed whine



## M640 (Nov 25, 2016)

Hello all, I'm throwing out a question or two in hopes someone may be able to explain what's happening in my controller. First some info.
1991 S-10 conversion, 5 speed, no clutch, ADC-4001 motor, Curtis 1231c controller, 144V drive setup, 18S 5P Leaf batteries for max 147.6V approx. 225Ah.

This has happened a number of times. I was driving today at 45-50 mph. I had just started driving so the controller was still cool and outside temp was approx. 68 degrees. Flat ground. At any speed from 45 mph and up, I'm usually pulling 180-200 amps to stay at that speed. I started the drive at 134 volts. After approx. 30 seconds to a minute at 45mph the controller started it's familiar curtis whine. There was no stuttering or jerking, no cutout just the same whine that the controller produces when starting from a stop.

My question is, any ideas on why there is a whine from the controller at speed? The first couple times it happened I thought maybe I didn't have enuf battery power to push me at that speed. Thinking that, I increased my battery pack from 18S 3P to 18S 5P. Even with the upgraded pack, same whine at almost the same speed. If it's just a whine and a natural part of the controller operation at higher speeds, I can deal with it. By the way, thank you in advance for any info.


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## remy_martian (Feb 4, 2019)

Does your whining go away after recharging the pack?

/pun sorta intended 😂


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## M640 (Nov 25, 2016)

remy_martian said:


> Does your whining go away after recharging the pack?
> 
> /pun sorta intended 😂


Lol, no, the whine is there no matter the charge level.


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## Electric Forklift Guy (Dec 13, 2012)

twiin640 said:


> Hello all, I'm throwing out a question or two in hopes someone may be able to explain what's happening in my controller. First some info.
> 1991 S-10 conversion, 5 speed, no clutch, ADC-4001 motor, Curtis 1231c controller, 144V drive setup, 18S 5P Leaf batteries for max 147.6V approx. 225Ah.
> 
> This has happened a number of times. I was driving today at 45-50 mph. I had just started driving so the controller was still cool and outside temp was approx. 68 degrees. Flat ground. At any speed from 45 mph and up, I'm usually pulling 180-200 amps to stay at that speed. I started the drive at 134 volts. After approx. 30 seconds to a minute at 45mph the controller started it's familiar curtis whine. There was no stuttering or jerking, no cutout just the same whine that the controller produces when starting from a stop.
> ...


Normally the controller runs at 15khz , it's ALWAYS loud but most of the time it's too high a frequency for you to hear.

During acceleration from a stop or overheat it drops down to frequencies as low as 1 khz.
( Anything below 10khz can be heard)

The hotter the controller gets , the lower the frequency.

If you are dropping below 2 khz while driving at speed it's getting really hot.
( Use a piano tuner app to determine the frequency)

Make sure

1. Air flows over the controller , it doesn't take a lot
2. The controller is bolted to a thick flat metal surface with thermal paste, that aluminum back plate carries the heat away from the MOSFETs.
You can make a good "heat sink" mount out of any flat piece of metal but if you Google "Curtis controller heatsinks" you'll find premade ones for your controller.

3.Make sure you don't have a loose motor brush or brush holder on your motor...this dramatically increases the current draw.
Make sure the brushes aren't stuck, they can become jammed in the holders and basically "float" above the commutator.

4.Because the MOSFETs are all in parallel it is possible for one or two to fail in a way that leaves the controller operational but nerfed to a lower current capacity. ( There's nothing you can do about it besides having it rebuilt or just live with it the way it is.)

Good luck , and if you find any issues or fixes to the overheat , I'd like to know what it was.


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## piotrsko (Dec 9, 2007)

While you are poking around, make sure the assorted fasteners are torqued properly. Stuff moves a lot when under high watt conditions.


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## M640 (Nov 25, 2016)

I had a 1/2" aluminum plate under the controller along with a fan. Air coming in the front, I think the Leaf batteries were just too far gone. I sold the truck and am on to another project. Thx for the info.


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