I accidently connected my Lyen controller in reverse polarity...

fredo gauvino

100 mW
Joined
Oct 11, 2009
Messages
39
Hello All,
I have a confession to make.
Recently I made a very very dumb mistake, and connected my newly built 12S A123 battery to my controller reversing the polarity. :shock:
It made a huge spark, and some wires got incandescent, melted down and I burnt myself while attempting to unconnect. my stupid mistake. I blamed lack of caffeine.
:oops:
I was surprised to see that the controller seemed to work ok when I had the polarity fixed.
Or it seems at first...
Without any load, the bike in the air, the wheel would spin normally when turning the throttle.
But as soon as the wheel got on the ground, and that I started rolling for 1 meter, it stopped forever.

But it stopped weirdly.
Like if two phases were shorted.
When pedalling with the controller connected but no battery, there is a lot of vibrating drag.
When disconnecting the controller, no drag.

I am sure that it is not the motor because it was not even connected when I reversed connected the battery...

So I opened the controller to find ... Absolutely nothing fried inside.

So my question : What component should I look for ?
Why does it short like this ?
When I connect the controller to the battery, it make a tiny spark that is 1/10 of what it was.
Could it be a capacitor ?

All mosfets look ok, I will try to test them tonight using method described from ebikes.ca

I have another controller but it is weaker, and does not brake. I would like to repair the Lyen if possible.

Thanks in advance for any insults or comments !

Fred
 
Here is the connector after removal. I forgot that those types of connectors mixes red and black when connected.
 

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fredo gauvino said:
But it stopped weirdly.
Like if two phases were shorted.
When pedalling with the controller connected but no battery, there is a lot of vibrating drag.
When disconnecting the controller, no drag.

That typically indicates failed FETs. Lyen can repair it for you, but if you want to try it yourself, there is troubleshooting info on http://ebikes.ca in the Learn -Troubleshooting section.

Capacitors can also be damaged (even if not visibly) by reverse current thru them. Sometimes they blow up, sometimes they just swell up (domed look) on the tops, sometimes they leak at the bottom, and sometimes nothing visible happens.
 
I unsoldered the faulty mosfet #3.
I retried the controller and it seems to work properly, except for some vibrations.
there is probably a fail safe check that prevents the controller from working if a mosfet is shorted...

It seems that I was lucky not to blow up other things!
Capacitor looks ok visually.

I just ordered 3 new irfb4310 100v from digikey.ca.

Thanks again for your help!
 
I've done this before with an infineon clone. I heard a pop, reversed the polarity, and it worked.
I was shocked at how it had a safety mechanism against stupid built into it.

Good thing your fix was on the easy side.
 
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