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Electric Unicycle's BMS problem and solution

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Chriull    1,604

 

 

@AURITA

I think that you have done wrong.

definitively. Aurita also shortened the control line - don't know if its bad for the control circuit or not. This detail is not in the schematics from hobby. But i would not recomment turning the wheel on or attaching the battery to the wheel before hobby gives a statement.

or aurita just takes a close look at the fotos and corrects her work... Reading the explanations would not hurt, too ?

Edited by Chriull

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AURITA    3

definitively. Aurita also shortened the control line - don't know if its bad for the control circuit or not. This detail is not in the schematics from hobby. But i would not recomment turning the wheel on or attaching the battery to the wheel before hobby gives a statement.

or aurita just takes a close look at the fotos and corrects her work... Reading the explanations would not hurt, too ?

what is wrong with it guys? ? dont understand..  Hobby told me to shunt the 2 mosfet in the middle..  @Chriull @vee73

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EUC Extreme    961

Three feet by no means be combined. This should be obvious. The same thing as removing the entire component and combine the circuit board together attachment points.
The miracle that your battery is still alive.

 

EDIT

I recommend to take the tin out as soon as possible. Hope you have a tin vacuum cleaner. Or suction sock.

Edited by vee73
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John Eucist    2,111

If the battery starts bulging, making sounds, or getting warm.  Be prepared for it to catch fire or explode.  Have fire extinguisher ready and keep the euc/battery somewhere that doesn't catch other things on fire easily like outdoors or in the bathtub or something.  Perhaps you did it right but only @hobby16 would know.  I would never do something like that unless I personally knew exactly what it is I'm doing.

Edited by John Eucist

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AURITA    3

Three feet by no means be combined. This should be obvious. The same thing as removing the entire component and combine the circuit board together attachment points.
The miracle that your battery is still alive.

 

EDIT

I recommend to take the tin out as soon as possible. Hope you have a tin vacuum cleaner. Or suction sock.

I just noticed now on the picture..  Omg... Will remover now the solder.. Thanks @vee73

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Chriull    1,604

If the battery starts bulging, making sounds, or getting warm.  Be prepared for it to catch fire or explode.  Have fire extinguisher ready and keep the euc/battery somewhere that doesn't catch other things on fire easily like outdoors or in the bathtub or something.  Perhaps you did it right but only @hobby16 would know.

from the schematics imho nothing serious should happen - just maybe the control cuircit for the mosfets could be harmed. But on the other side i would not turn it on* or attach it.

it's to be seen on the fotos that only 2 of the 3 pins are shunted. And drawn this way in the schematics. And additionally written to test the pins with a voltmeter if one is not sure about the pins...

 

*edit: ok - the bms is turned on all the time - so if something bad were to happen in 99% of the cases aurita would have already noticed it while soldering...

Edited by Chriull

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AURITA    3

from the schematics imho nothing serious should happen - just maybe the control cuircit for the mosfets could be harmed. But on the other side i would not turn it on* or attach it.

it's to be seen on the fotos that only 2 of the 3 pins are shunted. And drawn this way in the schematics. And additionally written to test the pins with a voltmeter if one is not sure about the pins...

 

*edit: ok - the bms is turned on all the time - so if something bad were to happen in 99% of the cases aurita would have already noticed it while soldering...

i have plugged it and it was charging as normal.. 

Now will take off the soldering and do it again.. 

So i just need to sold the middle and the right pin..  Right?

As the picture shows .. 

Will do it now @Chriull @vee73

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EUC Extreme    961

I believe that it is correct. As the hobby has meant. You used pewter quite a lot. Much less would have sufficed. At the same time the heat was too much component. I hope, however, everything is okay.
It would be best if, hobby ensure.

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Chriull    1,604

I believe that it is correct. As the hobby has meant.

Looks like. Normaly all the mosfets have a standard pin allocation - i do not know if there exists "exotic ones". But seems ok from the pcb layout - imho hobby16 has the expierience to confirm.

You used pewter quite a lot. Much less would have sufficed. At the same time the heat was too much component. I hope, however, everything is okay.

Its not to be seen clearly from the foto - but it seems to be not a nice soldering joint. Aurita - you can compare it to the pictures here: https://learn.adafruit.com/adafruit-guide-excellent-soldering/common-problems


It would be best if, hobby ensure.

?

 

if you do not/did not want to wait with charging/connecting the battery again it's a good idea to put it for the first try to a place where it cannot do some harm - just to be on the safe side

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hobby16    267

@Aurita

It's ok now.

Three feet by no means be combined. This should be obvious. The same thing as removing the entire component and combine the circuit board together attachment points.
The miracle that your battery is still alive.

Aurita had shunted the mosfet's gate (control line), not the thing to do but nothing catastrophic. It's a high impedance line so a short to 0V would not kill the battery, trigger an explosive fire and faceplant the rider or things like that. I hope so, anyway :D

If Aurita is harmed, burned and has his house on fire by the shunt, we'll know shunting is a dangerous job...

Edited by hobby16
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John Eucist    2,111

Gotway has early versions that cut-off but its recent BMSs don't, since the cut-off circuit has been removed.

How can I tell if my Gotways are recent enough?  I have one of the first Msuper HS 680 Wh, Two MCM2s+ 680 Wh, Two MCM2 340 Wh, Mten geared, and Mten non-geared.

 

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AURITA    3

Added Aurita's "Weerda" to the list of criminal wheels : http://hobby16.neowp.fr/2015/07/21/bms-shunt-list-of-wheels/

We can call them "criminal", right ?

i shunted it cuz this wheel was like that since I bought it and I'm getting a replacement tomorrow.. 

So will let u know if now is working properly or not.. 

Seems like everyone is scared that it get on fire.. Is that possible because now I'm a bit scared to plug it... ? @hobby16

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John Eucist    2,111

 

Seems like everyone is scared that it get on fire.. Is that possible because now I'm a bit scared to plug it... ? @hobby16

Only because this really old video went viral in last few days.  :D
 

 

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Chriull    1,604

i shunted it cuz this wheel was like that since I bought it and I'm getting a replacement tomorrow.. 

So will let u know if now is working properly or not.. 

Great - so had the chance to practice and you can make it proper with the new one, if needed!

if you first try the new one unshunted be careful and wear protectors when going faster and/or the battery gets lower!

Seems like everyone is scared that it get on fire.. Is that possible because now I'm a bit scared to plug it... ? @hobby16

imho the main reason for a fire are faulty battery cells - already from the manufacturer. So there is nothing you can influence.

for your modification there should be no problem - its just a safety measure, that you take a little bit more caution for the first test(s)

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John Eucist    2,111

Edmond Kwok on our Facebook group said this about shunting the BMS:
This will prevent overcurrent shutoff. But will circumvent the safety feature of preventing too much current going to a potentially bad cell or cells leading to a thermal runaway.

Since @AURITA 's euc kept shutting off right after turning on could it be due to a bad cell?

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AURITA    3

Edmond Kwok in our Facebook page said this about shunting the BMS:
This will prevent overcurrent shutoff. But will circumvent the safety feature of preventing too much current going to a potentially bad cell or cells leading to a thermal runaway.

Since @AURITA 's euc kept shutting off right after turning on could it be due to a bad cell?

i didn't have that problem anymore...  But it cutted off twice while i was riding it.. 

Great - so had the chance to practice and you can make it proper with the new one, if needed!

if you first try the new one unshunted be careful and wear protectors when going faster and/or the battery gets lower!

imho the main reason for a fire are faulty battery cells - already from the manufacturer. So there is nothing you can influence.

for your modification there should be no problem - its just a safety measure, that you take a little bit more caution for the first test(s)

will do that..  Thanks a lot for your help guys ?

Have someone posted that their wheel got fire after shunted a bms?

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hobby16    267

 But will circumvent the safety feature of preventing too much current going to a potentially bad cell or cells leading to a thermal runaway.
 

Sorry but it doesn't make any sense whatsoever ! A bad cell is bad precisely because it can NOT deliver too much current. An overcurrent situation can in no way lead to "too much current going to a bad cell", no way. And even if it were ever true, it would be still preferable than a faceplant.

So much nonsense in so few phrases that I'm at a loss at what that guy was thinking about.

As to the wheel on fire in the video, we could say that it's on fire because it is... NOT shunted. The irony !

Edited by hobby16
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John Eucist    2,111

 

As to the wheel on fire in the video, we could say that it's on fire because it is... NOT shunted. The irony !

I'm curious as to why shunting it would prevent the fire?

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hobby16    267

 

Have someone posted that their wheel got fire after shunted a bms?

That wheeler had shunted his SML and after two months of happy ride (without power cut, off course) had a mainboard fire (not a battery fire) : http://trottinetteselectriques.heberg-forum.fr/sutra21598_solution-probleme-bms.html#21598

Circumstances exclude that the cause comes from the BMS :

- the fire happend after a violent braking causing an overvoltage, killing the driver stage, provoquing a "shootthrough" in a half-brige and killing the mosfets.

- the SML is notorious for having a crappy mainboard, if there is a video showing how to change the mainboard, there must be some reason

I have no other feedback of a fire on a shunted wheel as of now. Even if there are other case, I'll keep all the shunt on my wheels, for obvious reasons. Rider security first.

I'm curious as to why shunting it would prevent the fire?

I was kidding.

What I meant, that a fire can happen, wether the wheel is shunted or not.

Edited by hobby16
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hobby16    267

@hobby16 could you reply to my question nine posts above about the Gotways?  Thanks!

Oh I forgot you. Look at the list of BMS here : http://hobby16.neowp.fr/2015/07/21/bms-shunt-list-of-wheels/

You can see that the most recent GW's BMS have just one small mosfet instead of at least 4 mosfets on all other BMS of the list.

The mosfets are the parts protruding the most under the plastic wrap, so take out the battery and touch the BMS to feel if you have many mosfet or one.

If just one mosfet, no shunt is needed.

Edited by hobby16
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