Please help! Smoking EUC motherboard, possible to fix?

[Tom]

I'm stupid. I was disassembling the case for my generic 350w EUC today and the ridiculous amount of hot glue covering the wires caused a capacitor on the board to bend over as I was pulling the wires through the casing.

When I turned it on a tiny amount of smoke started coming from the board so I disconnected power immediately and now nothing happens when I power on.

So my questions are, is my battery fried? Can the board be fixed? I'm a competent solderer and have some understanding of electronics, so I could replace the capacitors if required?

The bent capacitor

(I've assumed this was the cause of the problem, I pushed it back down but obviously that didn't do anything to help):

 

Overall board view (circled in red is the area the smoke was coming from):
 

 

[Tom]

If not, would this be a suitable replacement? It looks like the wires would fit but they are in a different configuration...

http://www.aliexpress.com/item/electric-wheelbarrow/1893729669.html

[robca]

Usually when the magic smoke comes out of a component, there's no way to put the magic smoke back in and have the component work again

It looks as if you didn't "bend" a capacitor, as much as ripped it open. Either when ripping it open or pushing it back, you created a short. An EUC has pretty big currents flowing, and a short is a serious one. Electrolytic capacitor shorting are really likely to cause damage, given how they are used in a circuit 

It might be worth trying to first replace the damaged capacitor, and powering up your board again. It would have been even better not to power the board with a ripped capacitor, but you might be lucky and the smoke was only residue burning off of an overheated resistor (unlikely, but you don't have much to lose at this point). Just make sure you try this in a fireproof place, and with an fire extinguisher close by. Also, use safety glasses, since some of the other capacitors could (in super-rare cases) vent/explode in case of shorts 

[Tom]

Usually when the magic smoke comes out of a component, there's no way to put the magic smoke back in and have the component work again

It looks as if you didn't "bend" a capacitor, as much as ripped it open. Either when ripping it open or pushing it back, you created a short. An EUC has pretty big currents flowing, and a short is a serious one. Electrolytic capacitor shorting are really likely to cause damage, given how they are used in a circuit 

It might be worth trying to first replace the damaged capacitor, and powering up your board again. It would have been even better not to power the board with a ripped capacitor, but you might be lucky and the smoke was only residue burning off of an overheated resistor (unlikely, but you don't have much to lose at this point). Just make sure you try this in a fireproof place, and with an fire extinguisher close by. Also, use safety glasses, since some of the other capacitors could (in super-rare cases) vent/explode in case of shorts 

Thanks, I've found an identical capacitor to replace it with so I'll give it a try. Also, I got this voltmeter so I can check my EUC voltage, do you know where I would attatch the 3 wires? Figure I might as well whilst I'm soldering here.

[esaj]

Thanks, I've found an identical capacitor to replace it with so I'll give it a try. Also, I got this voltmeter so I can check my EUC voltage, do you know where I would attatch the 3 wires? Figure I might as well whilst I'm soldering here.

3 wires? Voltage measuring should only require 2. Are you sure that there's no current-measuring involved or if the third wire is for powering the meter? Do you have some sort of datasheet or instructions from the seller for the voltmeter?

[Tom]

Ok, I've replaced the bent capacitor and now the controller powers on and the power LEDs are very dimly lit and there is a faint garbled buzzing coming from the speaker... I've ordered some capacitors to replace a few others, but I don't know if that will help. Is it possible to test capacitors whilst they are soldered onto the controller? Is it likely that it can be fixed or should I just drop the money on a new controller?

3 wires? Voltage measuring should only require 2. Are you sure that there's no current-measuring involved or if the third wire is for powering the meter? Do you have some sort of datasheet or instructions from the seller for the voltmeter?

It is this item on eBay - I think the third wire is for testing so I can ignore that?

[esaj]

It is this item on eBay - I think the third wire is for testing so I can ignore that?

Unfortunately, that looks like it's the kind of meter which needs separate input voltage, at least if the measured voltage is outside the range of 4.5-30V (which it is with our wheels, usually between 40 and 67.8V). So you need to add something to power up the display (a 9V battery would work just fine EDIT: On second thought, since there's no separate ground wire for the power supply, I'm not sure if you can hook it up like this... the ground should be shared with the measured wires, so you might need a step-down transformer, which might not be worth the price/hassle compared to just getting a display that can power itself directly from the measurement wires). This is what I did with the Firewheel, when I used a combined voltage/current-display, that needed separate powering:

A bit hard to see in the picture, but there are 3 wires coming from inside the wheel (ground, voltage measurement, current measurement, they're under the display, so not seen in the picture) and two separate power wires (seen in the picture) that go to that see-through plastic case (the white piece of equipment leaning on top of it is the Charge Doctor, I used it to calibrate the voltage display). Inside the see-through plastic case there's a 9V battery hooked through that red latching on/off-button to turn the display on and off.

If you don't want to add a separate power source, but to power the display directly from the batteries, something like this should work fine:

http://www.aliexpress.com/item/Red-7-150V-Reverse-connect-protection-2-wire-display-digital-voltmeter-100v-voltage-meter-head/32432257005.html?spm=2114.01020208.3.2.ZOPdYO&ws_ab_test=searchweb201556_9,searchweb201527_3_71_72_73_74_75,searchweb201560_4

Range: DC7-150V support 36V / 48V / 60V / 72V / 84V / 96V / 120V electric car
Supply voltage: DC7-150V 2-wire connection (Together with measuring lines)

That's the kind I'm currently using in the custom wheel (well, not exactly, the one I have also has calibration screw behind it), but I didn't (yet) add a button, so it's always on (even when the wheel is otherwise off):

 

[Tom]

Would this be suitable? It's next day delivery from the UK.

http://www.ebay.co.uk/itm/281473962869?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

 

Also, is it possible to identify this inductor (with the red X)? This is where the smoke came from so I think I should try replacing this too.

 

[esaj]

Would this be suitable? It's next day delivery from the UK.

http://www.ebay.co.uk/itm/281473962869?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Maybe, not sure, at least it seems the input voltage is (pretty much) the same as the measurement voltage, just wondering why they then use 3 wires at all. I'd expect it to work just fine with the measuring & input voltage coming from the same place, but not sure. There are those 2-wire 5-150V DC displays in Ebay too, but I guess they (usually) are sent from Asia, so if you need it fast, that might work just fine (or try to find a 2-wire version that ships fast?).

 

Also, is it possible to identify this resistor (with the red X)? This is where the smoke came from so I think I should try replacing this too.

 

That looks like a capacitor, not resistor (although I guess it could be a coil too, as it looks like there are "ripples" on the side?). Are there any markings in it or on the board where it connects (maybe on the other side)?  Here's a quick cheat sheet for PCB markings:

 

[Tom]

Thanks for the help! So where would I connect the wires to, the battery directly or somewhere on the mainboard?

Those are indeed spiral ribs on that component, I think the component is actually an inductor because it has this symbol under it:

[esaj]

Thanks for the help! So where would I connect the wires to, the battery directly or somewhere on the mainboard?

Assuming you want to measure the battery voltage, the battery, the connector between the batteries and mainboard or the points where the wires go in the mainboard are good. Or just branch from some of the wires in-between (peel or cut the wire, solder the measurement wire to it, insulate with shrink tube and/or electric tape). And of course make sure the polarity is correct    The displays are likely protected for reverse polarity, but then it won't show nothing but 0V (or maybe some error display, like blank or lines).

I think the component is actually an inductor because it has this symbol under it:

Yeah, looks like it, if you can somehow find out the type of the inductor used, you could try replacing it. 

[Tom]

I'v tried everything to identify this inductor coil, looking at photos of similar controllers I can see they are labelled but I can't read the label in pictures. If anyone possibly has a similar controller nearby with a labelled inductor I'd really appreciate knowing what this is so I can replace it, this seems like likely culprit.

 

[jayjay23]

Ok, I thought about that yesterday, but I knew it would require a bit of work, but if you ask so explicit, let me have a look.

I have the exact same board layout, but my induction has no writing on it, but I have a multimeter that can measure inductions, but you

have to unsolder them, so I will do that and let you know the value from the multimeter. I've worked with such inductions a lot

from my home automation project and if I got it right it's part of the voltage regulation, the EIB bus is 30V and adds data transmission

to the same two lines, so the voltage is not constant, but need to be keept by the regulation circuit, so I guess this is more or less the

same thing here, as the EUC battery gets some voltage drops to account for by the board.

[jayjay23]

Ok, here it is, it says 2.19mH so I think common number should be 2.2mH (btw measuring it while near or in the vise(metal!) it shows higher numbers (2.6-2.7) which should be wrong)

The recommendation I was given in the home automation project was to check every induction (this is why I have that multimeter),

as they sometimes come with long legs and if you buy plasticbag full of them, they get bend. And now due the construction there is

small thin wire wrapped around each leg and if the leg is bend to the wrong direction near to the ferite core that small wire easily

gets pulled apart, also soldering too hot can get the wire to be damaged somehow, or bending after soldering, and so on...

[Tom]

Ok, here it is, it says 2.19mH so I think common number should be 2.2mH (btw measuring it while near or in the vise(metal!) it shows higher numbers (2.6-2.7) which should be wrong)

The recommendation I was given in the home automation project was to check every induction (this is why I have that multimeter),

as they sometimes come with long legs and if you buy plasticbag full of them, they get bend. And now due the construction there is

small thin wire wrapped around each leg and if the leg is bend to the wrong direction near to the ferite core that small wire easily

gets pulled apart, also soldering too hot can get the wire to be damaged somehow, or bending after soldering, and so on...

Awesome, thank you so much for taking to time to do this for me! I've ordered a few of these to replace on my board now, lets hope it works! Hopefully I can repay with my guide on modifying the generic EUC casing, LEDs and adding a voltmeter into the case.

Thanks!

[jayjay23]

Your welcome. I now put it back on, I will check if it works again if I have build my battery packs as I only have a suitable power supply this way :-)

[Tom]

Your welcome. I now put it back on, I will check if it works again if I have build my battery packs as I only have a suitable power supply this way :-)

A fun project might be to build the controller into an external battery charging dock, I know that would be super useful if you have multiple batteries so you can charge whilst using your EUC.

[Tom]

Your welcome. I now put it back on, I will check if it works again if I have build my battery packs as I only have a suitable power supply this way :-)

Well. I have an unhappy update and resolution. I purchased the replacement capacitors and inductor and replaced them on the board. Turn everything on... bang! Lots more smoke coming out so I frantically disconnect the battery. I don't want to risk damaging the battery for the sake of a £25 mainboard, so I've ordered a replacement from AliExpress.

In the meantime, I purchased another generic for really cheap because my partner wants one to play with (but also so I don't have to be without EUC for 2 weeks ), but I noticed the case is much bigger than the other generic, I could fit another battery pack inside. Is it safe to simply solder the wires to connect 2 batteries to the EUC in parallel?

[Maxime]

Tom, usually, each batteriy comes with its own BMs card but this does not create a problem as far as I know.

[Tom]

Tom, usually, each batteriy comes with its own BMs card but this does not create a problem as far as I know.

Yes this is also my understanding. I was hoping I can solder the wires so 2 batteries share the same charge/discharge plugs, I don't know much more about batteries but I assume this would discharge the batteries at the same rate equally, meaning each battery drains half as fast?

[dmethvin]

Yes this is also my understanding. I was hoping I can solder the wires so 2 batteries share the same charge/discharge plugs, I don't know much more about batteries but I assume this would discharge the batteries at the same rate equally, meaning each battery drains half as fast?

Yes, that is the theory.  I am planning to do this for my Firewheel as well. The main thing is to be sure that the two batteries are equally charged before trying to put them in parallel. Otherwise the battery with a higher charge will immediately try to push the difference into the battery with the lower charge, and could damage it. An easy way to ensure this would be to charge each battery separately, then check the voltages with a voltmeter just to be sure. Once they are at the same level and connected in parallel, the EUC should drain them at the same rate.

[Tom]

Yes, that is the theory.  I am planning to do this for my Firewheel as well. The main thing is to be sure that the two batteries are equally charged before trying to put them in parallel. Otherwise the battery with a higher charge will immediately try to push the difference into the battery with the lower charge, and could damage it. An easy way to ensure this would be to charge each battery separately, then check the voltages with a voltmeter just to be sure. Once they are at the same level and connected in parallel, the EUC should drain them at the same rate.

I'm worried it may cause issues when charging, unless the charger can deliver enough power to charge both packs at once, won't there be some issue with that?

[jayjay23]

> Turn everything on... bang!

Bad to hear, but for the sake of curiosity it's always worth a try. Unfortunately it can always be that other components are damaged without visible outside changes.

Well but if you have a solution that's good anyway.

For my deleted controller I actually have thought the same, I will try to build a wheel from my left over components, which is now already a motor and a battery, so I could just buy the controller a shell and pedals and that's it to build one for my wife as she wanted to try it, but not with mine and she didn't wanted to spend lot more money :-)

[dmethvin]

I'm worried it may cause issues when charging, unless the charger can deliver enough power to charge both packs at once, won't there be some issue with that?

The charger is current-limited to 2 amps, at least most of the standard ones. The battery (or batteries) can't draw more than that, and the charger is fine with it. You could actually use one of those 4-amp quick chargers for two parallel packs and there should not be a problem. It will take twice as long to get to a full charge, but that's not a big issue since your battery is twice as big!

[Tom]

After replacing my mainboard, the EUC turns on and seems to go forward ok, but strangely it jerks / stuffers going backwards and it doesn't seem to balance backwards - if I slowly tilt the unicycle backwards it will go really far then suddenly jerk back. I've tried calibrating it and it just maintains a beep whilst the wheel spins in 1 direction. I've connected all the wires to their same colour counterparts, so I have no idea whats wrong.