# WOT fear for the brushed setup



## alex77roma (Dec 23, 2014)

Hi everybody ,
I have about a month from an Quantya used motorbike .
I like this bike for commuting in Rome , where is nimble in traffic and Has very good suspensions .
In the past I always used brushless system for my homemade electric bicycle with cromotor at 120 volts, and I never used brushed setup before this motorbike .
Reading all around in the web I learned that unlike brushless setup , if the brushed controller (Quantya has an Alltrax 4844) defeat I get WOT with my bike and I read that someone has got this bad problem.
I am very worried about it, I'm thinking to sell my bike or putting in a brushless system but in this case the problem is that it will be very expencive since I have to change motor, controller and battery also.
Am I exaggerated to worry so much?
All the peaple have brushed setup are quiet on this eventuality?


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## dragonsgate (May 19, 2012)

alex77roma said:


> Hi everybody ,
> I have about a month from an Quantya used motorbike .
> I like this bike for commuting in Rome , where is nimble in traffic and Has very good suspensions .
> In the past I always used brushless system for my homemade electric bicycle with cromotor at 120 volts, and I never used brushed setup before this motorbike .
> ...


What does WOT mean? I have not had any trouble with the brushes on my motors. If it is a full on blow out on the DC controller that you are concerned about then that can be a worry. I had one blow on me but it was from abuse. I would like to go AC in my car someday as there are some good setups now compared to what was available 15 years ago.


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## alex77roma (Dec 23, 2014)

WOT = Wide Open Throttle .

I read that if a brushed cotroller defeats , the motor get full power Directly from battery and it is very dangerous for mine or other people safety .


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## dragonsgate (May 19, 2012)

alex77roma said:


> WOT = Wide Open Throttle .
> 
> I read that if a brushed cotroller defeats , the motor get full power Directly from battery and it is very dangerous for mine or other people safety .


That is what I called full on blow out. I am running clutchles but have an emergency disconnect hooked up to the clutch peddle. From what little I know about it a blow out is most likely when the power is first turned on. That is when mine blew years ago. When I power up I make sure the car is in neutral. A precharge is supposed to help alleviate this problem a bit.


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## alex77roma (Dec 23, 2014)

Ok, I allready have a precharge resistor on my contactor, so I think I don't risk the WOT at power on, my worry is about the eventually that my alltrax suddenly defeat during the run.
If it becames on a corner in the road it would be very dangerous.


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## piotrsko (Dec 9, 2007)

I 've ridden a lot on the streets of LA, but I can't recall going into a corner with power on before. I have braked really hard, then pegged the throttle 3/4 through the turn, but that is just me in one of my more stupid moments.

I would run a switch/contactor on the handlebars that killed battery power as a fail safe. Should be enough time to kill the run-a-way before the turn.


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## alex77roma (Dec 23, 2014)

I had thinked about a stop engine button close the throttle but I am afraid because If the controller breaks, the motor goes in short circuit with the battery, takes all the max power that the battery can get and you can lose the control of the bike and it could not be possible to push the button for time.
I'm getting anxious, I know, but I am new to the brushed system and I have to understand if I can go relaxed or not.

PS. Sorry for my English, I hope I am explained.


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## alex77roma (Dec 23, 2014)

I read these two texts about the new SPM controller, are these characteristics of new SPM controller the solution to my worry?


"*Main Solenoid Control
This controller offers main relay control for safety. When the solenoid is wired to the Rly
Coil + and - tabs, the main relay drive is hardware interlocked microcontroller supervisor*"

And Also:

*"Advanced safety features (ASF) such as main relay Solenoid control, buss-bar thermal overload protection and ability to withstand output short circuits. Model variations with sealed connectors have features like rev limiting and CAN buss to further integrate the motor controller within the vehicle system, and provide forward compatibility with some upcoming amazing (and top-secret) new components*."


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## dragonsgate (May 19, 2012)

Alex, Anyone that can express their thoughts in a second language either verbally and or in writing does not have to apologize. What is your first language? I took a quick look at the altrax page and did not see anything about high peddle. I am sure piotrsko our one of the others can tell you more.


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## dougingraham (Jul 26, 2011)

A wide open throttle can happen with any kind of motor setup. It can occur when the throttle position sensor fails or if a mechanical linkage were to jam. The TPS failure is probably the most common reason. It is true that a brushed motor controller can fail shorted on and in fact both IGBTs and FETs typically fail turned on. The high voltage contactor is your friend in these situations. The better motor controllers have these built in and will detect a failure and open the contactor automatically. You can add your own like I have done where I can just turn off the key and the contactor opens and a failed controller no longer will matter.

I believe this is something that a person needs to be concerned about but it is not something you should worry overly about as it is an easy problem to solve.


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## EVfun (Mar 14, 2010)

A number of controllers have built in features to detect and stop a runaway WOT condition. These generally shut the controller down and lock if off in the event it detects the inability to turn the MOSFETs or IGBTs off. 

If you controller does not have this feature it is possible to add similar protection. The simplest is to have the main contactor open each time the throttle is released (but keep the precharge circuit on so the controller is ready to go when you hit the throttle again.) This doesn't lock out in the event of a failure, will will insure power is removed from the motor every time you release the throttle. 

You can add a reed switch to a power wire that will close when current is flowing through one of the motor power wires over some low level. You then use a switch that closes when the throttle is released in series with that reed switch to engage a latching relay. That relay latches when current is flowing (reed switch) and the throttle is released (throttle switch.) The latching action takes the power away from the contractor, causing it to open, and the latching action keeps it from closing again.

There are other ways to add this type of protection to a DC motor controller that doesn't have it built in, the ones above are the 2 ways I've seen.


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## dragonsgate (May 19, 2012)

I had two contacts when I first built my car. It is an effective way to safeguard against runaway but in stop and go traffic the clack clack of the secondary contact opening and closing annoyed the crap out of me. I have would considered reinstalling it if I can figure out how to make it not so noisy.


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## alex77roma (Dec 23, 2014)

Thank you everybody, I really appreciate Your Tips. 

@dragonsgate:
I am Italian.

@everybody:
At the moment I already have a contactor in series (on the negative wire) and the primary key that stops the conctactor circuit.
Also have a precharge resistor, but as Dragonsgate wrote, I think don't like the "clack" every time I open the throttle because I have a motorbike and the contactor is very close to me and my ears and also I think this continuous working linked the throttle switch reduces the life of contactor...Am I wrong about it?

At the moment, I think the easy (but expensive) solution could be buying the new Alltrax SPM controller that as a logic that control the contactor and some other protections.


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## dragonsgate (May 19, 2012)

alex77roma said:


> Thank you everybody, I really appreciate Your Tips.
> 
> @dragonsgate:
> I am Italian.
> ...


I thought so. Fiat is about as close as I come to speaking Italian. I have been driving them for almost 40 years and have owned several plus one Alfa. As far as wear of contactors go if you have a good quality one it should last for a long time.


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