Is it safe to connect all 3 motor vires and use it as a brake ?

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liteglow   100 µW

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Is it safe to connect all 3 motor vires and use it as a brake ?

Post by liteglow » May 22 2018 5:49am

Hi

I`m new here, and not so sure where other place I can ask.
It seems like this is the site that have all info there is about chineese motor controllers and HUB motors :)

So, the question. I have a kids car that I have mounted 2x 10" Hub motors from a Hoverboard (Self leveling board etc).
I then connect the motors to a chinese motor controller 350W, the controller looks like all other controllers to bikes etc that is made in China.

My motor controller have a "Brake High Signal" (Yellow), I try to connect this cable to GND\5V+ and 12V+.
But there is nothing that happen, when I connect it to 12v or more, the motor stopp accelrating when it is rotating, but there is no force to stop the motor, so if you have speed it will stop accelrating but continiue to roll.

This is not safe on the little kids car

So I had an idea to use 3 relay to shorten the 3 wires from the motor, this will disconnect the motor from the controller also.

I know that when you connect the 3 wires you will have alot of force that will stop the wheel from rotating, but will it build ut heat etc or other possible bad scenarios ?

I will also use this solution on a sefety stop switch, so whenever I need to stop the car instantly anyone can push the Emergency stop button.



Thank you for helping out :)


(edit: sorry for my bad English, hope you can ignore it)

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eee291   10 kW

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Re: Is it safe to connect all 3 motor vires and use it as a brake ?

Post by eee291 » May 22 2018 12:14pm

Like you said it builds up heat and a lot of force on the axle, but nothing else really.

If you are willing to open the Controller you might find a pcb hole marked ''EBS'' If you connect it with a switch to ground, it should do regen braking.

liteglow   100 µW

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Re: Is it safe to connect all 3 motor vires and use it as a brake ?

Post by liteglow » May 22 2018 1:06pm

eee291 wrote:
May 22 2018 12:14pm
Like you said it builds up heat and a lot of force on the axle, but nothing else really.

If you are willing to open the Controller you might find a pcb hole marked ''EBS'' If you connect it with a switch to ground, it should do regen braking.
OK, thank you for the reply :)
The heat and force on axle is not an big issue, as the breaking will be of very short amonunt of time.
The kid and the car is not that heavy, and it will stop at a short time I guess :roll:

I did as you said, open the controller. But there is no hole marked EBS or anything similiar.

As I understand there is thousand different controller, so maybe I need to try out some other that maybe work.
The only hassle is that I want to build this car as as 4WD, so I need to buy 4 controllers that is working like.

The buy the controllers I have now because of the "reverse" function, that actually works out pretty well :)

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amberwolf   100 GW

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Re: Is it safe to connect all 3 motor vires and use it as a brake ?

Post by amberwolf » May 22 2018 1:12pm

Keep in mind that while you *can* use something like a switch or relay to short two or three motor phases, you first have to ensure they get disconnected from the controller, or else it'll probably be destroyed by the short.

Also, if there's enough vibration, the switch or relay could engage accidentally, at random, and create braking when you don't want it.

Also, the switch or relay will have to be able to handle the full phase current, which can be many times higher than the battery current, and have to be able to switch that current reliably without ever welding the contacts. If it isn't rated to do this, it could weld the contacts together for either braking or controller side, and then as switching completes it shorts the controller out and blows it up.


The pads on teh controller board could be marked a number of things; I'd recommend looking up Regen and Pad on ES to see what others have posted as possible markings to look for. There's a lot of irrelevant hits, but definitely some that have potentially useful info.

search.php?keywords=regen+pad&terms=all ... mit=Search

liteglow   100 µW

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Re: Is it safe to connect all 3 motor vires and use it as a brake ?

Post by liteglow » May 25 2018 2:27pm

Hi again and thank you for the tips.

I did some and have done some searching here :)
There should be no problem using a relay, as it will be a NC\NO relay.
So when there is no power to the relay they are Normally Closed, on Power they are Normally Open.
This way it`s absolute impossible to have they shorted the same time the controller is giving the motor power.
The wire to motor cant have both.

Anyway, I tested this today on one motor, and the speed is reducing, but not 100%, it`s more like driving in mud feeling. But it helps.

I did also got my throttle today, but it does not work.
I dont know if my controller is "special" or stupid, but the only way to make it work is to have 2 switches.
One switch make the wheel goes SLOW, swithc and then it goes FAST, use the second switch and it will go even FASTER.

Adding a throttle does nothing..

Here is my controller:

https://www.ebay.com/itm/36V-350W-Brush ... 2749.l2649


and here is the throttle I have:

https://www.ebay.com/itm/Universal-Elec ... 2749.l2649


I want this car to work with both Brakes, Throttle AND reverse!
I can find many controllers for bike that have throttle and regen\Brake, but not reverse.
Maybe it`s not possible to find both?


I want to buy 4 new controllers to this car (4X hub motors) 4 wheel drive.
But before I buy 4 new one, it would be nice if anyone can reccomend any that they know can fit my needs :)

Thank you again for all help.



(sorry for some spell errors, Google Chrome Auto correct dont work)

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Chalo   100 GW

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Re: Is it safe to connect all 3 motor vires and use it as a brake ?

Post by Chalo » May 25 2018 2:48pm

Note that using relays to short the motor phases means switching a load with lots of inductance. You'll get arc damage over time, if not immediately. Consider using solid state relays that have much higher voltage ratings than your operating voltage (to accommodate inductive voltage spikes). SSRs usually are designed for only AC loads, but can often be switched by DC signals. That's what you want in this case, because your signal voltage are DC but the brushless motor makes 3 phase AC. If you use SSRs, you will need one per motor phase.

Are you confident that the added heat load on the motors won't be a problem?
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ElectricGod   10 MW

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Re: Is it safe to connect all 3 motor vires and use it as a brake ?

Post by ElectricGod » Jun 14 2018 7:03pm

What these guys said...just use regen and recover that energy instead. Otherwise you will deal with complications form destroyed contacts and possibly blowing your controller...or worse.
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Re: Is it safe to connect all 3 motor vires and use it as a brake ?

Post by billvon » Jun 14 2018 9:29pm

liteglow wrote:
May 22 2018 5:49am
So I had an idea to use 3 relay to shorten the 3 wires from the motor, this will disconnect the motor from the controller also.
Here are the issues.

1) Tremendous braking torque at high speeds, zero braking torque at zero speed. So it may lock your wheel at speed, but may not keep the motor from turning when stopped or almost stopped.

2) Tremendous voltages. When you use the brake and stop using it before you have stopped, you will have built up a lot of current in the windings. When you open the switch it has nowhere to go, and the inductance of the windings will turn that into a very high voltage.

3) Heat. All that mechanical energy has to go somewhere, and it will turn into heat in the system you described.

If you want to do something fancier, use a controller that has regen. Or do it yourself. Put in your relay, then on the "brake" side of the relay put in six diodes - three from phase to B+, three from phase to B-. Then use either a mechanical relay or MOSFETs to short and unshort the windings. This will give you PWM braking. If you connect the diodes to the battery you will get regen. If you connect them to a resistance you will dissipate it as heat, but in the resistor, not the motor.
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liteglow   100 µW

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Re: Is it safe to connect all 3 motor vires and use it as a brake ?

Post by liteglow » Jun 15 2018 2:57am

Thank you for the answer.

I dont have regen on my 4 controllers, and not so sure if I want to buy 4 new ones.

But I could build my own regen as you said.
Or turn that power into something else.
That is a good idea.

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