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Marty Backe

My 84-volt Nikola Triumphs, Tribulations, and Failures

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On 6/13/2019 at 12:14 PM, Dzlchef said:

@Marty Backe the wheel charged fine although the battery seems to carry me about as far as my KS16S, albeit much smoother and faster.   I need to learn to start slower and keep a consistent cruise speed.  

https://euc.world/tour/575803514399088

Wow. That’s really surprising.  I have a ks16s as well and can only go about 15 miles before the battery is so low I don’t wanna ride it anymore.  But my fist ride on the nikola I started at 90% and went 22 miles. A mixture of fast stop and start and 25 mph riding and I only went down to 46 % and I’m 6’3” and 200lbs.    So I will get at least 45-50 miles out of her 

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36 minutes ago, EU_commuter said:

@Marty BackeWhich wheels survived the Overheat Hill?  MCM5 certainly.  MSX?  How about any Kingsong wheels?  Thank you.

Personally I've never had another wheel fail on Overheat Hill. I've had wheels overheat though. I've seen KingSong wheels blow a fuse, and a ACM2 blow a MOSFET (not my wheel). The MSX flew up the hill no problem. The KS18XL (18S too) made it up the hill, but overheated.

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55 minutes ago, Marty Backe said:

IMG_0484

 

IMG_0483

 

 

So sorry to hear of this failure for you and for Gotway. Lotta beeping going on there! You said you set the alarm at 90A. I'm not great with electronics, but would you set it at the same on a 100V wheel? Arrrg, so disappointed at the smaller mosfets!

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29 minutes ago, Kens said:

OMG we can put some IKEA furniture inside that shell :laughbounce2:

Thank you Marty for your sacrifices and R.I.P Nikola. :innocent1:

Btw will 100v control board works with 1600wh battery? :confused1:

No, the 100-volt wheels use a different battery configuration.

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So @Marty Backe now that you have had a little time to think, what happens with your NIkola. Is it going to be your city wheel? I couldn't imagine you taking it to mountain trails after what happened.

Then again it might be a weak component that didn't live up to expected standard I guess. These thing does happens. 

I didn't know you got hurt in the process. I hope you are OK. Good thing you had protection gear on. 

Again cummunity comfort pad on the shoulder to you. 

200.gif&ehk=UWSKqIWgfAD6YfQwuQmh1w

 

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2 minutes ago, Unventor said:

So @Marty Backe now that you have had a little time to think, what happens with your NIkola. Is it going to be your city wheel? I couldn't imagine you taking it to mountain trails after what happened.

Then again it might be a weak component that didn't live up to expected standard I guess. These thing does happens. 

I didn't know you got hurt in the process. I hope you are OK. Good thing you had protection gear on. 

Again cummunity comfort pad on the shoulder to you. 

200.gif&ehk=UWSKqIWgfAD6YfQwuQmh1w

 

Thanks :D

Unfortunately, I will not be able to take this wheel on any rides that contain longish steep hills. Too delicate. I'll always have to be monitoring the current alarm for sure.

Let's hope Gotway moves to a better control board for the 84-volt version.

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1 hour ago, Seba said:

You're right. It also seems that there is no temperature probe near the radiator or MOSFETs. This is a major design flaw, as PCB temperature where temp probe is apparently located in Nikola, being additionally cooled by the fan located on wrong side, doesn't reflect MOSFET tab or package temperature. This is why @Marty Backe got misleading, very low temperature readings. For example, in KS-18L/XL there is a temperature probe located close to the heatsink and MOSFET that is farthest from the cooling fan. This is why L/XL may be perceived as a "hot running wheel". Nikola wasn't "cold running wheel", it was just a "very hot running wheel with low temp readings".

From what I see, PCB design may cause MOSFET source (S) leg to overheat, as there is highest thermal resistance due to small copper pad directly under the MOSFET leg. I don't see the other side, but i assume it's similar so drain (D) legs are also connected using small pad located on an edge of larger copper plane.

Another design flaw is to use two TO-220 MOSFET instead of one TO-247. Doubled small package design is prone to many failures. MOSFET leg fracture during bending or PCB assembly will increase leg resistance. Improper soldering or improper PCB design may cause current imbalance, so it wont be divided 50/50 between both transistors. And if one MOSFET will fail, but won't short, second MOSFET failure is a matter of short time, as it takes over full current instead of part of it. As we can see in the photo, it was the case. Failed both MOSFETs on one side of a motor phase half-bridge circuit. Double MOSFET design may work well only if is properly oversided, so each single MOSFET is able to carry maximum current expected to flow in the motor phase circuit. But as failing MOSFET will likely create a short circuit, secondary MOSFET won't be beneficial.

I think the bigger question is if GW uses the 247’s, are they just moving the problem further down, like to the motor or motor wires.  As you’ve seen from EUC Guy pushing his wheel to the limits, 247’s held up well, but the motorwire insulation melted resulting in a short.  When motor gets too hot, it also affects the magnets, they demagnetize or the glue becomes undone,,.

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7 minutes ago, eddiemoy said:

I think the bigger question is if GW uses the 247’s, are they just moving the problem further down, like to the motor or motor wires.  As you’ve seen from EUC Guy pushing his wheel to the limits, 247’s held up well, but the motorwire insulation melted resulting in a short.  When motor gets too hot, it also affects the magnets, they demagnetize or the glue becomes undone,,.

I need to inspect my motor wires now and again because i live in hilly area and sometimes do big hills where i get 90amp beeps/ vibrations often , I've had it nearly a year now 

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4 hours ago, Marty Backe said:

But Gotway really screwed up by going cheap on the MOSFETs. It's a mystery :facepalm:

 

4 hours ago, Marty Backe said:

I have learned my lesson that I will not buy another Gotway wheel that doesn't use the large MOSFETs!

I'm really sorry for you, but thanks for the test.
So the Nikola 84V is out of the 16X or Nikola 84V purchase decision for me!

Now the question is back again....16X or Nikola Plus 100V with bigger 247's mosfets, even if this means maybe less torque for higher speed.

But what does it look like in the Plus version? I can't imagine that it looks any different there, except for the other mosfets?
I suppose we're expecting the same design flaw there as @Seba wrote and I see it the same way, don't you?

3 hours ago, Seba said:

It also seems that there is no temperature probe near the radiator or MOSFETs. This is a major design flaw, as PCB temperature where temp probe is apparently located in Nikola, being additionally cooled by the fan located on wrong side, doesn't reflect MOSFET tab or package temperature. This is why @Marty Backe got misleading, very low temperature readings. For example, in KS-18L/XL there is a temperature probe located close to the heatsink and MOSFET that is farthest from the cooling fan. This is why L/XL may be perceived as a "hot running wheel". Nikola wasn't "cold running wheel", it was just a "very hot running wheel with low temp readings".

 

I can only agree with that.

1 hour ago, eddiemoy said:

That is why there is a fuse in the KS wheels.   Even if the firmware screws up, the hardwired fuse would blow and then everything is saved.  Just need to replace the fuse, not the board or motor. Fuse blowing in the KS wheels are rare, but it does happen.  It still results in a face plant. No way around that, but just replace the fuse and if you are properly protected, can ride again.  No need to wait for replacement components to ship. BTW, with everywheel, you get spark fuses.

Unbelievable, I would have assumed that a fuse would be standard.

KS  :thumbup:
Gotway :eff04a58a6:

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