My 84-volt Nikola Triumphs, Tribulations, and Failures

[meepmeepmayer]

30 minutes ago, US69 said:

Yes, sure, then probably all the dozens of Mosfet Blows of the old Mosfet case have been due to insufficient heat dissipations…

Actually, that's exactly what happened. For example, the old msuper V3/ACM hill failures showed that the mosfets generally blow at the same time the thin motor cabling back then melted. Usually, it was the mosfets, but sometimes it was the cabling. So they had a reliable ceiling what they could or could not do (which was about the same as the cabling's ceiling). I count the few insta-exploding mosfets as bad from the start, and they simply died at the first sign of a real current. The point is, mosfet behavior is predictable.

I know you want to make a distinction between high current and overheating, but isn't that 99% the same?

Again, my shitty ACM mosfets were stronger than the cabling. So it is reasonable to assume the stronger Nikola mosfets were really just a victim of the bad board assembly/lack of cooler contact.

Whether the Nikola currents really are higher (or just reported as higher) and how the wheel will behave on the overheat hill with a good board is still unknown. Yes, the low temperature reading is conspicuous but it might very well be that properly cooled mosfets will survive much longer and the temperature (wherever it is measured) will have gone up by then, so the wheel will just throw the standard overheat warning.

We'll see.

Edited June 19, 2019 by meepmeepmayer
spelling

[Nils]

1 hour ago, TuN3M@N said:

"this thing is not able to read current"  -- Really? Mine provides very nice relative current measurements like all my other Gotway wheels.

Ok, now  i understand that you are really thinking that this thing was throwing nearly continuous 90Ah current. Sorry but it wasn´t. 

While it's never a good idea to feed the trolls, I encourage you do to please get some research done before commenting. The current Gotway wheels report is the motor phase current, which should not be a surprise to anyone doing their home work. Hence the phrase "relative current measurements" used by Marty above. You might think this is bad or incorrect or not, but that's neither here nor there.

[Marty Backe]

1 hour ago, LucasD said:

Are those amperage reading accurate?

I see my Mten3 spike to 90-100A when doing pendulums...

Personally, I consider the current value to be mathematically derived and not necessarily an absolute value. But I think all Gotway wheels use the same method for reporting this value. Empirically, I have settled on 90-amps as a value that represents a very high current draw within the wheel. I don't worry if I get period 90+ amp power draws but I do worry (and stop whatever I'm doing) if I get near continuous 90+ amp measurement for more than a handful of seconds.

Yes, reversals cause huge spikes in power. Any wheel can be overheated by doing continuous pendulums. I have done this to overheat wheels on purpose (to confirm the temperature that causes the wheel to overheat).

[mrelwood]

4 hours ago, US69 said:

it reduced A BIT of the heat  removal

The difference an inproper installation does to heat transfer is not very intuitive, as just a tiny gap of air will have a huge effect. I have no doubt that plastic melting and moving under the Mosfets may dramatically reduce cooling efficiency.

Example: CPU overclockers compare differences between thermal paste from different manufacturers, even when the point of the paste is only to fill the surface incostencies, not form a layer between the CPU and the cooler.

That said, going with the smaller Mosfets was a risky decision from GW. Also their talks about optimizing energy management for the smaller Mosfets turned out to be nothing more than hot air (see what I did there? ). Combine these three, and Marty showed us what happens.

Edit: And the fact that the thermal probe didn’t register the overheating Mosfets (and the unnaturally cool readings from all GW wheels) suggest that the probe is located ”safely” away from the Mosfets.

Edited June 19, 2019 by mrelwood

[Harold Farrenkopf]

1 hour ago, mrelwood said:

The difference an inproper installation does to heat transfer is not very intuitive, as just a tiny gap of air will have a huge effect. I have no doubt that plastic melting and moving under the Mosfets may dramatically reduce cooling efficiency.

Example: CPU overclockers compare differences between thermal paste from different manufacturers, even when the point of the paste is only to fill the surface incostencies, not form a layer between the CPU and the cooler.

That said, going with the smaller Mosfets was a risky decision from GW. Also their talks about optimizing energy management for the smaller Mosfets turned out to be nothing more than hot air (see what I did there? ). Combine these three, and Marty showed us what happens.

Edit: And the fact that the thermal probe didn’t register the overheating Mosfets (and the unnaturally cool readings from all GW wheels) suggest that the probe is located ”safely” away from the Mosfets.

The plastic film was carelessly left on the heat conductive pad. It looks like the assembler pulled the film from one end and it ripped and they went to the other end and pulled it and that ripped too but they didn’t notice that some remained on the sheet. It was there all along creating a high resistance to heat conductance. 

[Marty Backe]

26 minutes ago, Harold Farrenkopf said:

The plastic film was carelessly left on the heat conductive pad. It looks like the assembler pulled the film from one end and it ripped and they went to the other end and pulled it and that ripped too but they didn’t notice that some remained on the sheet. It was there all along creating a high resistance to heat conductance. 

And in the industry that I'm in, if this was discovered, ALL units assembled by that worker would be recalled and either inspected or replaced. I'm pretty sure Gotway just shrugs their shoulders and continues on  

Edited June 19, 2019 by Marty Backe

[Seba]

On 6/16/2019 at 2:26 AM, meepmeepmayer said:

I'm too wondering if it was only a build quality problem, or if the wheel would have fried anyways due to design. That unusually high current needs to be explained.

Definitely this design has several flaws that I wrote about many posts ago. Inefficient forced cooling, using small MOSFETs in paralell configuration, PCB layout that is not thermally optimized. Of course this only my personal opinion, but it's  backed by my experience as an electronic design engineer. I made some mistakes with thermal design in my history. Next what's important; seems there is no thermal probe located near to MOSFET cases or heatsink. Instead, there may be temp probe located on top (component) PCB side, thus measuring PCB temperature. As glass substrate is a poor thermal conductor, especially when cooled by fan, this temperature will not correlate with heatsink temperature and will show low values. There also may be no dedicated thermal probe at all - both MCU and IMU contains temperature sensors. Gotway could use one of them (or both) to limit costs. But this is just a guess.  Anyway, this design may still work for most situation without failure. There will be just less safety margin or it will fail only in severe load conditions that are very unlikely for most use cases. 

Anyway we shouldn't rely on WheelLog values reported! They are good for showing some trends, but not exact values. In case of Gotway we don't get real amperage! It's a somewhat arbitrary value. More, we don't know if Nikola values are in line with MSX values. WheelLog gets just numbers - for example 27 may stand for one ampere. But this may be true for just one wheel type. With another, one amp will be equal to value of 35. I know that you may trust WheelLog, but you shouldn't. And I say it with full confidence as an active WheelLog developer.

The only reliable way to verify this is to measure real currents with calibrated shunts or current probe, then compare it to values received from wheel over BT data link. Then we could check if they agree in some way and determine scaling ratio / offset value. 

It would be also a good idea (because of simplicity) to make comparision of two wheels at the same time - say, MSX and Nikola, with the same battery capacity. We get two riders of the same weight and ride the same track, with the same speed at the same time and location. Then we can compare battery voltage. If both wheels are similar in energy efficiency (this will directly reflect current, as both batteries are of identical voltage), we can safely assume they draw similar currents. But if one wheel is clearly more efficient (as it gets more range under similar conditions), we can assume that the other wheel is less efficient, thus drawing more current. But it's just an approximation.

[Unventor]

26 minutes ago, Marty Backe said:

And in the industry that I'm in, if this was discovered, ALL units assembled by that worker would be recalled and either inspected or replaced. I'm pretty sure Gotway just shrugs their shoulders and continues on  

Might be, but the QC inspector should be more worried. If something like this should not be there it should have been spotted. 

However I don't know what is right or wrong assembly since I have no insight in GW designs. 

But I think @Sebas point on design makes sense.

Could this happen at other companies, I am afraid so. We have seen batch issues the past year from all major brands that released new wheels the past year. 

I do hope this doesn't happen with the KS16X... I am perfect cable to crash it myself, don't need factory help 😉

[Unventor]

What do you think @Marty Backe 9B makes break assistance for Z10. Power breaking takes ⚡

GW went a different route ☄️😏

Inmotion forgot that outside San Diego it rains at times 🌦️🌡️

KS forgot size do matter outside China, axel vs rider🤔

It is often small thing that make a huge impact. 

I just wounder what could be cooked up for KS16X, it would be too perfect if it doesn't have something.... 

Edited June 19, 2019 by Unventor

[Lukas83]

guys it's so easy: 

Marty will probably get a new board from Jason (warranty?), put this nasty thing (without film residue of course) back in the Nikola and I'm pretty sure that he will repeat the test riding up the hill like the cops are after him. If it's passing the test, WE ALL will be SURE it was only the crappy plastic leftover under the mosfet. If not we can keep blaming gotway for to small mosfets... 

cheers and thank u in advance Marty 

[Hunka Hunka Burning Love]

 Nice new wheel!  I didn't quite make it through reading all 19 pages of this thread , but sorry to hear about the disappointing MOSFET failure on the steep hill climb.  I think it's important to remember that these electronic gizmos do have their limits.  That hill test is pretty much an extreme case which most wheels aren't purposely designed for.  I wonder if we did a survey, how many people would say that they absolutely need an EUC to be able to climb such a steep hill for a prolonged period of time?  How many of us have actually done a similar hill climb?  Probably not a huge number of people.

It's almost like expecting all cars to be able to run the 24 Le Mans road race.  Unless the car is purposely engineered to survive something as grueling as that, most likely will fail.  These consumer grade EUCs are likely targeted at the average person's needs.  They have come a long way in accommodating heavier western riders with larger feet, but they really haven't made huge leaps.  It is getting there slowly but surely.  Do we all wish EUCs could climb the steepest hills and never fail?  Definitely!  But I think if we are honest with ourselves and understand the reality of it all, the Nikola will perform just fine for the majority of riders out there within a reasonable range of riding conditions.  It's too bad it didn't fail gracefully though (ie. tiltback to allow rider to dismount and wheel to cool) as that would maybe allow people to forgive it's steep hill climbing failure.

[meepmeepmayer]

This is much more likely than not a manufacturing defect (thermal pad plastic cover not fully removed). Marty will repeat the test with the new board and I suspect (= hope) it's just going to overheat (at most) then, just like all the other wheels.

[TuN3M@N]

8 hours ago, Nils said:

While it's never a good idea to feed the trolls, I encourage you do to please get some research done before commenting. The current Gotway wheels report is the motor phase current, which should not be a surprise to anyone doing their home work. Hence the phrase "relative current measurements" used by Marty above. You might think this is bad or incorrect or not, but that's neither here nor there.

Maybe it is phase current maybe not, but what means this for the controller input? Is the phase current lower than the controller input current? Think about it... 

BTW. Next one who becomes personal... Nice style... 

BTW2. If another guy says the same that the GW current readings are not real all you guys like it... Nice

Edited June 19, 2019 by TuN3M@N

[Marty Backe]

19 minutes ago, Hunka Hunka Burning Love said:

 Nice new wheel!  I didn't quite make it through reading all 19 pages of this thread , but sorry to hear about the disappointing MOSFET failure on the steep hill climb.  I think it's important to remember that these electronic gizmos do have their limits.  That hill test is pretty much an extreme case which most wheels aren't purposely designed for.  I wonder if we did a survey, how many people would say that they absolutely need an EUC to be able to climb such a steep hill for a prolonged period of time?  How many of us have actually done a similar hill climb?  Probably not a huge number of people.

It's almost like expecting all cars to be able to run the 24 Le Mans road race.  Unless the car is purposely engineered to survive something as grueling as that, most likely will fail.  These consumer grade EUCs are likely targeted at the average person's needs.  They have come a long way in accommodating heavier western riders with larger feet, but they really haven't made huge leaps.  It is getting there slowly but surely.  Do we all wish EUCs could climb the steepest hills and never fail?  Definitely!  But I think if we are honest with ourselves and understand the reality of it all, the Nikola will perform just fine for the majority of riders out there within a reasonable range of riding conditions.  It's too bad it didn't fail gracefully though (ie. tiltback to allow rider to dismount and wheel to cool) as that would maybe allow people to forgive it's steep hill climbing failure.

However, all wheels from the last two years made it up this hill. So actually I do expect modern performance wheels to survive this ride. And if they do I can have confidence that I can ride them anywhere.

If nothing else my test demonstrated the importance of proper heat-sinks for our wheels, and, if Gotway ever hears about this, maybe better assembly for future wheels.

[Michael Tucker]

It seems as if there are two issues being discussed, and neither one is definitively being addressed. Instead we argue over possible design ideas and theories of math and science.

Issue #1: Was the board/heatsink assembled and installed correctly.

Issue #1 Answer: People who own a Nicola can open theirs and look for themselves (post photos). Marty will receive a replacement and also inspect.

Issue #2: Is the reported high amps normal and safe for the Nicola.

Issue #2 Answer: Only time will tell, like previous blown MOSFET issues. People will report if their wheels start dying. Even Ian at SpeedyFeet captured a blown MOSFET on cam while riding his old 84V Monster up a slight hill. If the MOSFET design is a problem, it will become obvious. Our sport relies on people riding and reporting their experiences. This is where ideas and theories are not as important as real-life experience and past performance.

LONG LIVE THE MSX...THE TRUE PERFORMANCE KING!

[Marty Backe]

13 minutes ago, Michael Tucker said:

It seems as if there are two issues being discussed, and neither one is definitively being addressed. Instead we argue over possible design ideas and theories of math and science.

Issue #1: Was the board/heatsink assembled and installed correctly.

Issue #1 Answer: People who own a Nicola can open theirs and look for themselves (post photos). Marty will receive a replacement and also inspect.

Issue #2: Is the reported high amps normal and safe for the Nicola.

Issue #2 Answer: Only time will tell, like previous blown MOSFET issues. People will report if their wheels start dying. Even Ian at SpeedyFeet captured a blown MOSFET on cam while riding his old 84V Monster up a slight hill. If the MOSFET design is a problem, it will become obvious. Our sport relies on people riding and reporting their experiences. This is where ideas and theories are not as important as real-life experience and past performance.

LONG LIVE THE MSX...THE TRUE PERFORMANCE KING!

Unfortunately this is an impossibility. Only a destructive inspection is possible based on the control boars assembly and how the MOSFETs are secured to the heatsink. Therefore I will not be inspecting my replacement control board.

[Michael Tucker]

1 minute ago, Marty Backe said:

Unfortunately this is an impossibility. Only a destructive inspection is possible based on the control boars assembly and how the MOSFETs are secured to the heatsink. Therefore I will not be inspecting my replacement control board.

I see. There is a quality or design problem suspected and no way to visually verify correctness. I ride fast in the hills every night and initially I was quit enthused by your reports on the Nicola, of course now this issue is a serious problem for me. I don't think I could trust the Nicola in a high performance setting.

Thank you so much Marty for doing these tests and posting your findings.

[Marty Backe]

18 minutes ago, Michael Tucker said:

I see. There is a quality or design problem suspected and no way to visually verify correctness. I ride fast in the hills every night and initially I was quit enthused by your reports on the Nicola, of course now this issue is a serious problem for me. I don't think I could trust the Nicola in a high performance setting.

Thank you so much Marty for doing these tests and posting your findings.

I don't know if you ride any Gotway wheels. But just to be clear, whomever/whatever is assembling the Nikola control boards is assembling all Gotway control boards. So I do not consider this a Nikola only issue.

[fryman]

2 hours ago, meepmeepmayer said:

This is much more likely than not a manufacturing defect (thermal pad plastic cover not fully removed). Marty will repeat the test with the new board and I suspect (= hope) it's just going to overheat (at most) then, just like all the other wheels.

That’s if the wheel is registering the proper temps. It seemed to me and others that the wheel was registering very cool temps for the stress it was under. 

[Lucas Alexander Oliver]

I feel pretty confident with my nikola on any normal hill in all normal parameters.. everyone got so upset about Marty’s wheel burning up    So maybe it’s not a mountaineering wheel but I will ride the hell out of it around Seattle on hills and whatnot. No problem.  It’s an amazing wheel and I love it.  Even though I had an issue with my 45 degree cutoff getting stuck.    It’s not perfect but it’s fun enough to forgive.  IMHO at least.  

[Jon Stern]

8 minutes ago, Lucas Alexander Oliver said:

I feel pretty confident with my nikola on any normal hill in all normal parameters.. everyone got so upset about Marty’s wheel burning up    So maybe it’s not a mountaineering wheel but I will ride the hell out of it around Seattle on hills and whatnot. No problem.  It’s an amazing wheel and I love it.  Even though I had an issue with my 45 degree cutoff getting stuck.    It’s not perfect but it’s fun enough to forgive.  IMHO at least.  

If there's a MOSFET cooling issue, their lifetime could be badly impacted. If Marty hadn't ridden overheat hill, they might have failed on shallower inclines after weeks or months of normal riding.

[Marty Backe]

1 minute ago, Jon Stern said:

If there's a MOSFET cooling issue, their lifetime could be badly impacted. If Marty hadn't ridden overheat hill, they might have failed on shallower inclines after weeks or months of normal riding.

I attribute the failure to a one-off workmanship error. I have to hope this error is not wide spread. Otherwise it's hopeless and we may as well stop riding all wheels. It's a calculated risk, I know.

[Lucas Alexander Oliver]

21 minutes ago, Jon Stern said:

If there's a MOSFET cooling issue, their lifetime could be badly impacted. If Marty hadn't ridden overheat hill, they might have failed on shallower inclines after weeks or months of normal riding.

 That’s true with everything.   They are all going to fail eventually.  Just be as safe as you can at all times and enjoy yourself.   That’s how I have to look at it.   I love to wheel.  It is the best feeling I’ve found in a sport like hobby.  And I know it’s dangerous and expensive.  But the reward is way more than worth the risk.   So keep on rolling people  👍👍👍✌️🤘🏻😉🤩😍😍

[Hatchet]

How much money did GW save going with smaller MOSFETS, haha! They attained near-perfection with the legendary MSX, flew too close to the sun I guess and the Nicola burned.

 

[Lucas Alexander Oliver]

29 minutes ago, Marty Backe said:

I attribute the failure to a one-off workmanship error. I have to hope this error is not wide spread. Otherwise it's hopeless and we may as well stop riding all wheels. It's a calculated risk, I know.

Considering the sheer number of nikolas out there and the fact that so far yours are the only MOSFETS that have blown and they blew only with some manufacturing errors and under extreme conditions .. I like to think that the nikola is  pretty damn tough. And that the blown ones were kinda a fluke.     Maybe the bigger MOSFETS would be better but the hundreds or thousand out there seem to be doing fine so far.  So all in all I think it’s safe to say the nikola is pretty damn bad ass.   I love it. And may buy the plus version when Jason gets them in so my wife will ride the 84 v and I’ll ride the 100v.    They are great wheels. All around.       Great design great power. Wonderful comfortable feel. And as long as you buy them from @Jason McNeil and ewheels you can be confident that you’ll be taken care of no matter what happens .   I can’t stress enough how important that customer service is when dealing with this tech.   Don’t find out the hard way. buy from a reputable dealer who will stand by their sale.  Jason at Ewheels.com !!   Just my two cents for the day!