Sherman died

[HippoPig]

So, what do we think happened guys?

 

thankfully - I wasn’t riding it. Had got it out to go for a ride, turned it off to put my gear on and it wouldn’t come back on.

 

 

[Tawpie]

Warranty claim time. 

[HippoPig]

17 minutes ago, Tawpie said:

Warranty claim time. 

It’s being collected tomorrow 👌🏼

[DjPanJan]

First is good you not get hurt.

Looks like thermal damage you experience some burn smell?

What version sherman you have old display or new red buttons version?

You try some big inclines or long hills before?

What pedal seting you use soft/medim/hard?

What is you mileage and weight if is not secret?

I feel with you and hope you will be riding again soon.

 

 

[fbhb]

6 minutes ago, DjPanJan said:

What version sherman you have old display or new red buttons version?

L20-20 version number printed on the control board and the size of the transformer would suggest an early/1st batch Sherman.

Edited May 17, 2021 by fbhb

[Planemo]

Weird. Heat damage seems localized to that central motor wire mount? Almost seems like the capacitors have popped too...?

[HippoPig]

1 hour ago, Planemo said:

Weird. Heat damage seems localized to that central motor wire mount? Almost seems like the capacitors have popped too...?

Yeah - it’s very weird.

 

I don’t think it’s a typical failure.

[HippoPig]

2 hours ago, DjPanJan said:

First is good you not get hurt.

Looks like thermal damage you experience some burn smell?

What version sherman you have old display or new red buttons version?

You try some big inclines or long hills before?

What pedal seting you use soft/medim/hard?

What is you mileage and weight if is not secret?

I feel with you and hope you will be riding again soon.

 

 

Hard setting.

 

weigh about 11 stone approx.

I could only smell the burning when I opened her up.

 

no, not at all - I ride with my partner who uses an 84v MSX.

 

300 miles total 😳

2 hours ago, fbhb said:

L20-20 version number printed on the control board and the size of the transformer would suggest an early/1st batch Sherman.

Number 78

Edited May 17, 2021 by HippoPig

[Chriull]

11 hours ago, HippoPig said:

thankfully - I wasn’t riding it. Had got it out to go for a ride, turned it off to put my gear on and it wouldn’t come back on

Seems it somehow got too much motor current flowing for one of the motor wire connections.

Would be interesting if a mosfet blew up. And the fuses, too. Or the fuses even saved the mosfets?

From your description it died while trollying it outside, turning it off before/after standing/leaning it somewhere and then turning it on.

Dead while trollying should have been noticed, so while stopping/leaning/holding the wheel during turning it on and off.

In earlier times there were much more wheels dying while leaning/standstill. Current limiting while standstill is a very delicate problem for the firmware - on the one hand the components have to be protected from the huge possible currents (motor is about a short circuit during stand still) but on the other need a considerable torque to start riding...

Is there a chance the screw holding the motor wire was not perfectly fixed?

In your first picture there could be some wire thread/solder thingie going from the motor wire in direction to the lower capacitor? Causing a short? Or is this just an artifact?

2 hours ago, DjPanJan said:

You try some big inclines or long hills before?

Some pre"damages" by high burdens of this contact seems very sound, too.

1 hour ago, Planemo said:

Almost seems like the capacitors have popped too...?

Most looks like dirt from the wire sleeve or  heated up?

Just the one spot on the lower capacitor could be a very small leak where he "blew out"?

The little bit of bulging could be perspective distortion/just the plastic wrap?

11 hours ago, HippoPig said:

So, what do we think happened guys?

... hard to limit the possibilities without further detail... Imo will be still hard to say even once more is known.

But these pictures imho show a big weak spot/design fault of the sherman:

The high current wires are directly beside the capacitors! The capcitors are heat sensitive and have on the outside just some "thin" plastic wrap an on top and bottom bare naked metal. Like both legs not insulated.

Beside the blackened motor wire between the two capacitors the 4 battery wires are _soldered_ (shiver) directly beneath one capacitor.

And all four battery wires are without the protective heat resistant sleeves. 

So no real wonder that on many pics of dead shermanns exactly this spot is a big hole, charred all around...

One should not underestimate the power of 10p li ion cells - especially not if one designs an EUC...

[Planemo]

A loose screw on that central post was my first thought too.

As for the other concerning areas, plenty of shermans havent got heat damage whilst under high speed, let alone at a standstill like this one.

[Chriull]

59 minutes ago, Planemo said:

A loose screw on that central post was my first thought too.

Or whichever other contact problem.

Interesting that there are steangely molten solder spots on the screw.

59 minutes ago, Planemo said:

As for the other concerning areas, plenty of shermans havent got heat damage whilst under high speed, let alone at a standstill like this one.

I was a bit offtopic with my other comments about pictures of fried sherman boards after (slow speed) overburdening.

[HippoPig]

4 hours ago, Planemo said:

A loose screw on that central post was my first thought too.

As for the other concerning areas, plenty of shermans havent got heat damage whilst under high speed, let alone at a standstill like this one.

It was definitely tight when I put it back together.

 

it was definitely loose when I opened it up to investigate.

 

what should I expect in terms of repair? What needs replacing for this to be safe?

Edited May 17, 2021 by HippoPig

[Planemo]

20 minutes ago, HippoPig said:

It was definitely tight when I put it back together.

Oh, had it been apart then? I didn't know that. Was the post screw secured with silicone?

20 minutes ago, HippoPig said:

 

it was definitely loose when I opened it up to investigate.

Ahh! So it was loose then! That is highly suspicious- the amount of current going through a wheel would definitely create huge heat through a non-sound connection. The only query is why it just happened to happen when you weren't riding it...or maybe you were just very lucky...?!

Personally I don't think I would risk anything other than a new board, but others may think differently.

[Chriull]

36 minutes ago, HippoPig said:

what should I expect in terms of repair? What needs replacing for this to be safe?

Does the tire turn freely with the wheel turned off?

How does the capacitor, which was near the wire sleeve look like in detail?

Why are there solder spots on the screw?

Why are the two other screws tight, but this one was not? What is the difference - silicon, glue, circlip, snap/lock ring, etc?

It could have loosened again after you screwed it down? By this something missing to keep it tight despite all vibrations?

From what is known and seen by now most likelly the "left" capacitor plus the connector on the motor wire. The screw and maybe the thread in/on the printed circuit board. Some copper tracks around this connection on the pcb? ...

15 minutes ago, Planemo said:

Personally I don't think I would risk anything other than a new board,

+1! Should be the best advice!

And bears the advantage of newest firmware plus motherboard version!

Plus the burned motor wire connector has to be replaced - in a "perfect" way. Plus all three wires tightened to the motherboard in a better way than this middle one...

[RockyTop]

I know that I am late to the party.  It looks very typical for a loose connection or broken wire. I see the wire itself as damaged at this point. I would replace as much of that wire as reasonably possible. (6 inches) 

[fbhb]

1 hour ago, Chriull said:

+1! Should be the best advice!

And bears the advantage of newest firmware plus motherboard version!

Plus the burned motor wire connector has to be replaced - in a "perfect" way. Plus all three wires tightened to the motherboard in a better way than this middle one...

@Chriull is spot on, as usual, in All of his recommendations. I know from personal experience that this is a very early version control board. There have been several revisions since L20-20 with accompanying firmware updates, the latest being L20-42! A brand new control board is a must IMHO along with the other recommendations mentioned.

Edited May 17, 2021 by fbhb

[supercurio]

Thanks for sharing @HippoPig!
I'm adding that to the list of things to check when my Sherman will arrive: are these connection solid.

Would you recommend adding silicon in order to secure these?
If so, should it be any alkoxy silicone, or only high-temp silicon?

I wonder about protecting the capacitors further as well.

 

And I really appreciated reading through the collaborative root cause analysis from everyone 

[HippoPig]

2 hours ago, Planemo said:

 The only query is why it just happened to happen when you weren't riding it...or maybe you were just very lucky...?!

Personally I don't think I would risk anything other than a new board, but others may think differently.

I’m expecting a new board as a minimum.

Theres a step from the hallway, where the wheels live, into the kitchen. That’s all I can think of.

[Chriull]

2 hours ago, supercurio said:

I'm adding that to the list of things to check when my Sherman will arrive: are these connection solid.

Would you recommend adding silicon in order to secure these?
If so, should it be any alkoxy silicone, or only high-temp silicon?

In ecodrifts teardown nothing but the screw, the eyelet, a washer and some ?plastic insulation cap? is to be seen.

Personally i'd add something to secure the screw against vibration, but i have no experience with this.

Maybe the tightening from @HippoPig was too much or not enough? Or the screw got some grease/oil or something else crazy happened during assembly?

An experienced opinion regarding such screwed connections would be great.

2 hours ago, supercurio said:

wonder about protecting the capacitors further as well.

That's something i'd definitely do if i'd own a sherman.

No possibility for any motor or battery wire to touch or heat the capacitor! With something isolating and (very) heat resistant.

Edit: btw: If the Sherman reports motor current like the Begode wheels (which is imho true?) one should use an app to set a motor current alarm to save the wires and mosfets! Afaik some 80-120A are common for Begode wheels? 120A maybe already a bit too much? Or they are ok for short durations?

Edited May 17, 2021 by Chriull

[Killface]

At least it is fixable and you weren't hurt!

[fbhb]

3 hours ago, Chriull said:

Personally i'd add something to secure the screw against vibration, but i have no experience with this.

Maybe the tightening from @HippoPig was too much or not enough? Or the screw got some grease/oil or something else crazy happened during assembly?

An experienced opinion regarding such screwed connections would be great.

Leaperkim Do now actually provide each of the cable securing screws with both a Flat washer and a Spring locking washer from the factory, plus a spot of Black silicon to help with the motor cables security.

In my own personal experience of needing to replace the control board on 2 occasions now, in both instances the New replacement control board was supplied with New screws and the 2 sets of washers washers. 

When I carried out the first board replacement, I found All 3 screws were torqued down very tightly to the point where they produced the typical squeaking sound when unscrewed.  A Philips screwdriver with a nice snug fit was necessary to also avoid chewing the slots due to their tight fit.  If at this point, the Old screws are slightly stripping their threads,  they will need to be discarded and the New replacements used but are definitely a must to use on any New board if a good secure connection is to be achieved.

This is my original L20-34 version control board before I removed the motor cables and the Black silicon can just about be seen on the screw heads.

This is a comparison of the Original L20-34 control board and my First replacement L20-42 board.

NOTE: The distinguishing, separately mounted smaller transformer and also the replacement New screws and washers supplied with the New L20-42 board.

Edited May 18, 2021 by fbhb