# Controller failure in full-on state?



## loragen (Jan 27, 2016)

Has anyone encountered a DC motor controller that has failed such that it provides full power all the time? That is, when the main contactor is closed the vehicle goes to full acceleration. It has not happened in my experience, but I'm curious if it ever has?

Thanks much for any info you could share.


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## RIPPERTON (Jan 26, 2010)

Its happened here in Sydney about 6 years ago on the first boot of a conversion.
I wasnt there but a friend of mine booted up the ctlr, possibly a curtis and the throttle was wired wrongly and the motor went to full rpm and centrifuged its commutator.
I usually use those cheap aligator clip wires you get from the electrical store as phase cables so if I do get a full throttle signal on the first boot, it smokes the wires not the motor. They work on light throttle just so I can get the hall timing right and make sure the throttle is wired up right then replace them with proper phase cables.
You could do the same with a DC motor.


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## dragonsgate (May 19, 2012)

loragen said:


> Has anyone encountered a DC motor controller that has failed such that it provides full power all the time? That is, when the main contactor is closed the vehicle goes to full acceleration. It has not happened in my experience, but I'm curious if it ever has?
> 
> Thanks much for any info you could share.


I have told this story before but incase you haven’t heard it I had a Curtis controller blow full on about a year after the conversion. I didn’t have proper cooling and I was enamored with the low end tongue. Luckily I had an RPM limiter so the motor would rev to 5K then shut down right a way. I was heading out for another fun drive and was about a mile from home when I heard a noise like a marble being dropped into a tin box. I turned around and got it home. I didn’t have an auto opening garage door at the time so when I got back in the car to pull in the garage she blew. The car was in neutral when I turned it on and the controller was behind the seat at that time so when it went it was a large sounding explosion and lots of smoke in the cab. I hit the silk so to speak. I mean I never moved so fast before. As soon as I was out of the car I realized what had happened and the motor only cycled through a couple on and off rev’s before I managed to get back to shut it off. I have had other cooling issues Curtis controller for a while until I finally cut the ends out of the controller and put a blower on one end and blow air directly through the controller. The controller is high and dry in the trunk with a sock filter. I have had the controller apart a couple of time over the years and everything looked clean and in good shape. I monitor the temp in the summer and with this setup it has never gotten half as hot as it did with a finned heat sink.


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## loragen (Jan 27, 2016)

Dragonsgate - Thanks for sharing the story again. I'm new to the forum and had not heard it before. Good thing you had the external rev limiter. 

Did you happen to do a post-mortem autopsy of the controller? Do you think the failure was due only to excessive load/heat, or were there any other clues to why it failed full-on? 

Ripperton - Thanks also. About the same thing happened to the Electric Racing Team that I advise (I'm a teacher), when the students miswired the throttle on a PMC controller and the race car blasted into the side of the building. But that was due to a wiring error, not the spontaneous failure of the controller. I'm trying to learn if/when/how a DC motor controller could fail in a full-on state.


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## major (Apr 4, 2008)

I believe member EVfun experienced a full-on failure in his buggy. There was a post/thread a few years ago where a newly installed EPC controller went full-on at start up. John Wayland's White Zombie failed this way due to mis wiring. I've had converters and devices fail shorted (full-on) on the bench. 

It only takes once to get into trouble. And it can happen. So be careful out there. 

major


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## dragonsgate (May 19, 2012)

loragen said:


> Dragonsgate - Thanks for sharing the story again. I'm new to the forum and had not heard it before. Good thing you had the external rev limiter.
> 
> Did you happen to do a post-mortem autopsy of the controller? Do you think the failure was due only to excessive load/heat, or were there any other clues to why it failed full-on?
> 
> Ripperton - Thanks also. About the same thing happened to the Electric Racing Team that I advise (I'm a teacher), when the students miswired the throttle on a PMC controller and the race car blasted into the side of the building. But that was due to a wiring error, not the spontaneous failure of the controller. I'm trying to learn if/when/how a DC motor controller could fail in a full-on state.


Miswiring and crashing into the wall is a good reason to have the car on stands with the drive wheels off the ground when working. I have never had that mishap with my EV during all the years of tinkering but I did just about run over my self when working on my 4X4. I had been working on it most of the day and had it all tuned it up and just before I closed up my work shop for the night decided to reach in and fire it up one more time. It did fire right up but the dam thing was in reverse. Luckily if you if you can call it that the shop doors were closed and stopped my cruiser enough to kill the engine. Otherwise it probably would have gone out and down the hill into the creek. Next day I put a switch on the clutch so the peddle has to be pressed down to start the vehicle. As for the controller blowing I am sure the fact that I did not have adequate cooling and I had my foot all the way down every time I drove the car. One of my reasons for opening up the ends on the Curtis besides cooling was I figured the explosion was so loud and did so much damage was because the blow out happened in a sealed container. Did you ever put a firecracker in a tin can? Any kid will tell you that you get more bang for the buck in tin can. When the cap blew the explosion was amplified by the extra pressure. It shredded the control board which I am sure is what caused the full on mode. Only one cap was blown and the end plug on the housing came out like a small missile. That blow out happened in 2000 and ever since I say to my self when I start up is this the day this POS is going to blow up again? That is why I put it in neutral before I push the start button. I am pretty sure if it ever blows the energy will pass through the open ends and do less damage. Something I hope I will never find out.


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## Vanquizor (Nov 17, 2009)

My Logisystems controller failed full on about 5 min after initial install. Nothing was showing signs of getting warm let alone broken kinds of hot. The failure occurred the first time I rolled on the throttle more than half way- or more accurately as I lifted off the throttle after rolling onto it. Cycle Analyst showed I drew 15kW, as I rolled off throttle it drifted down to 8kW, hiccuped then blasted off... I hammered on the brake- power draw went up to ~40kW then I hit the key- the contactor did its thing and the excitement was over. I lifted off the brake and let it roll towards my alley with smoke pouring out from under the hood.



It was actually far less exciting than when the inter cooler hose blew off on the draw through turbo setup on my '85 Daytona hanging it WOT, but thats a story for another day.


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## EVfun (Mar 14, 2010)

major said:


> I believe member EVfun experienced a full-on failure in his buggy. There was a post/thread a few years ago where a newly installed EPC controller went full-on at start up. John Wayland's White Zombie failed this way due to mis wiring. I've had converters and devices fail shorted (full-on) on the bench.
> 
> It only takes once to get into trouble. And it can happen. So be careful out there.
> 
> major


Oh yeah! It was a lowly 400 amp Curtis 1221B controller but when that failure happens it isn't just full on -- it is all your batteries can dish out until you shut if off or something else yields. I dropped 120 volts worth of Optima into a Prestolite MTC motor and the torque was so huge that the brakes couldn't stop the tires from spinning. I had the front locked and the backs burning rubber while I was accelerating away (without steering as I had the front tires locked.) The ride stopped when I turned the ignition switch off. That took several seconds as I was hurling backwards when it happened and it is very hard to take your eyes off the direction you heading into without control!

Modern DC controllers should have controls to prevent that. I replaced the old and dumb Curtis with a new and smart Zilla. That controller shuts off for some microseconds several times per second and if it doesn't find pack voltage across the IGBTs it shuts off the main contactor (and throws error codes and don't want to turn back on.)


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## dragonsgate (May 19, 2012)

EVfun said:


> Oh yeah! It was a lowly 400 amp Curtis 1221B controller but when that failure happens it isn't just full on -- it is all your batteries can dish out until you shut if off or something else yields. I dropped 120 volts worth of Optima into a Prestolite MTC motor and the torque was so huge that the brakes couldn't stop the tires from spinning. I had the front locked and the backs burning rubber while I was accelerating away (without steering as I had the front tires locked.) The ride stopped when I turned the ignition switch off. That took several seconds as I was hurling backwards when it happened and it is very hard to take your eyes off the direction you heading into without control!
> 
> Modern DC controllers should have controls to prevent that. I replaced the old and dumb Curtis with a new and smart Zilla. That controller shuts off for some microseconds several times per second and if it doesn't find pack voltage across the IGBTs it shuts off the main contactor (and throws error codes and don't want to turn back on.)


I remember you telling about that. Backwards at full on! You could probably sell tickets for a ride that exciting.


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