The R pack wirebond issue

[Mark911]

You can prevent future throttle faults due to reverse rotation by removing the reverse spring inside the throttle and epoxy shut the little spring cavity (keep the tiny reverse plunger in place). Some folks didn't want to do this because we assumed Alta would release a variable braking or reverse mode using the reverse motion of the throttle. Won't happen now, at least by Alta anyway.

 

[snydes]

Why don’t bond it back? There are low temperature hardening conductive glues..

I was looking for any such products and wasn't able to find anything. Could you link such a product?

... and also very low temp solders.

The OEM fuse wire would not take solder for me. Perhaps with a different method? I had no luck trying.

 

[rayivers]

The OEM fuse wire would not take solder for me.

If the fuse wire's aluminum, I've had the same problem. There's at least one guy at Endless Sphere who's successfully using soldered copper fuse wire (thread).

 

[snydes]

@rayivers , it’s definitely an aluminum alloy. We speculate it was something the manufacturer of the wirebonder specified for their process. There would be options for using a tinned copper wire in place of the aluminum, but then you are altering the characteristics of the original fusing. Would this ever be a problem? Likely not, but if you were unlucky enough to have that one cell out of the 504 suffer some sort of internal failure then it could be a bad thing.

The next issue with trying to repair a code 36 pack is this;


This was a ride where I rode the bike down low on charge, approximately 7% where this data was taken. Look at the voltage on my problem group.... yikes!!!! What do we think that is going to do to those 5 cells being discharged that low? Pretty disappointed the BMS didn’t prevent that from happening. So if you have a code 36 pack, I’d suggest not taking it below 15% SOC in order to not run those problem groups into the danger zone. At least that way you can limit the damage to them. Another good reason to have MultiTool to monitor your battery health.

 

[enjoythesilenc]

I was looking for any such products and wasn't able to find anything. Could you link such a product?

The OEM fuse wire would not take solder for me. Perhaps with a different method? I had no luck trying.

Interesting study:
Effective Method for Wire Bonds Rework Using Conductive Epoxy

interesting product:
https://www.amazon.com/MG-Chemicals/dp/B08PDDFS3V

interesting company in SF no less:
https://proprecisionprocess.com/

"Need Wirebonds fixed? NO PROBLEM. We have 101 ways to do this."

Perhaps less interesting ideas bouncing around my cranium, probably not included in the aforementioned "101 ways":

1. the component size we are dealing with is similar in scope to what jewelers and dentists use. Laser welding could work to reattach the loose end of the fuse wire tp the top of the cans SPOT Jewelry Laser Welder Welding Machine 200W In-Stock, US Seller,US Service | eBay

2. Imagine a barrel stave. There is a small radius of the outer edge of the cell exposed by the notch in the PCB. Take a strip of the casing from a deconstructed Sony cell. Force the strip down along the side of the cell leaving a good portion exposed. You now have only a mechanical joint but one with much more surface area than the original wirebond. you can spot weld or whatever else you want to do with the new negative "tab" far away from the fragile plastic insulating disc located in the critical area of interest.

3. more to come once these get shot down

 

[rayivers]

There would be options for using a tinned copper wire in place of the aluminum, but then you are altering the characteristics of the original fusing. Would this ever be a problem? Likely not, but if you were unlucky enough to have that one cell out of the 504 suffer some sort of internal failure then it could be a bad thing.

I must have missed this reply... if the original fuse characteristics could be roughly determined by measuring an intact aluminum fuse link, then doing some web research on resistance per unit length & what other similar packs are successfully using, it should be possible to come up with a copper (or other suitable / solderable metal) functional equivalent. I'd think a slightly-higher-than-OEM blow point would be ideal in this case, as I wouldn't want to introduce a 'weak link' and in a HV series string there's no shortage of fusing.

 

[snydes]

I think if there truly was a cold solder/epoxy product that was low resistance enough, that could be the best reasonable avenue. I have a feeling though it would not be the miracle product we would like. Any mechanical contact type repair has the potential to be jarred loose and do all sorts of bad things. There may be ways to ensure it stays put but then I’d be concerned about the quality of the connection. Any soldering is really sketchy and potentially dangerous. If the failed connection wouldn’t be on the crimp/negative end (which it almost always is), it wouldn’t be as scary though.