Posted on 7 Comments

Tesla’s 100kWh – Achilles’ Heel Uncovered

I can’t believe it, but the 100 kWh pack, which has been refined from previous generations, has failed on me (and it’s not the cells causing the issue). The problem lies in a flaw we’ve been observing in fossil-fueled vehicles for the past 20 years: aluminum wire bonding. The same problem that TEMIC has failed, either by accident or on purpose, to resolve in the automatic transmissions of VAG and MB over the last 20 years, affecting 80 million vehicles, is now appearing in the 100 kWh battery. The only manufacturer we’ve noticed who has nearly perfect ultrasonic wire bonding is BOSCH, as they adhere to some “secret” recipes for long-term reliability that we observe in the aftermarket. Meanwhile, Temic, Conti, and others continue to make the same mistakes, as does Tesla in this specific case, where they didn’t account for the thermal expansion of the battery module both in width and length, nor the potential galvanization of the “wire sense” flat cable connection. Designing a battery system without any flaws is impossible, but if you ask me, I certainly wouldn’t have failed in these connections, where the wire is too short from the terminal plate to the flat cable used to measure the voltage of one group. All 16 modules in the battery system had 5 to 7 damaged connections, and the ones that suffered the most were those parallel to the longer part of the module (red line), where the expansion was greatest, resulting in the most damaged groups. Based on previous documented cases, which we couldn’t address because they were under warranty, it seems that all 100 kWh batteries will fail between 150,000 and 250,000 km. The good news is that they will never suffer from classic moisture penetration, as they have a new generation of vapor-permeable valves, lack fuse covers on the top side, and don’t have some of the other faults of previous generations (our trade secret). Furthermore, the “batteries” will never fail, i.e., the individual cells, as we estimate that the cells themselves can last over 600,000 km. However, a repair of the entire battery due to unaccounted thermal expansion will likely be necessary, but after that, it will never have this problem again because we fix it permanently!

This 100 kWh battery system has a black metal cover, meaning it is a REMAN battery (already serviced), but the problem has been documented on non-REMAN systems as well. The side effects I’ve noticed include the range dropping overnight more than usual, but this is not a rule. The only clear indication is the drop in BMS parameters by 4 kWh, from 88 to 84 usable. As a result, the range parameter in kilometers on the dashboard decreased after two consecutive charges. A third parameter was visible through measurements with our EVC Explorer tool, where one module showed noise in the voltage measurement. The worst part is that the battery started failing on the highway, but AIDBOX saved the day, acting as life support to get us to our destination. For all other Tesla 100 kWh battery owners, most of whom are still under warranty, an essential battery system service awaits them, which we have only just discovered.

Repair is not easy and cheap, soldering is not possible because it is aluminium (thermal expansion cracks soldering attempts), 10000-15000€ equipment needed beside 40-60 labor hours to finish it. This should not be done by any DIY workshops or any other untrained personel. You risk destroying battery pack.

Error code: BMS_f107, BMS_w177

Affected cars: Model X and S from 2016 – 2021
100D P100D Longrange

7 thoughts on “Tesla’s 100kWh – Achilles’ Heel Uncovered

  1. Owning a 2020 MY Raven Model X I just discovered your post on LinkedIn. Being concerned after reading this, what is your recommendation for me at this point not having noticed any of those issues yet? Does it make sense to proactively do anything about this or do I just wait until this happens?

    1. You cant do anything about it. When it fails we can repair it and improve it so it doesnt fail ever from that cause.

  2. As for my understanding. The connections will fail and the pack will lose cells this way. The missing cells will decrease the capacity of the whole pack. Will you replace the „lost cells“ since they will be empty and permanently damaged once they’re depleted? After it went through a repair in your shop the pack should have its original capacity back. Is my assumption correct?

    1. Had did you manage to write and understand everything completely wrong.

      1. How shall I ? Sense wiring breaks. Lost connection to a whole bunch of cells. Capacity is decreased. How shall I misunderstood that wrong ? The only thing that I’m curious is about is the fact that my car already says it has capacity of 84 and below sometimes even 82,8 and fluctuating but I still have no bms vsh error

  3. Again a very good article. Thanks.

    There are feedback from companies like Recell that those issues with bonding on voltage sensor harnesses are often occuring when the battery pack has suffered an impact (see extract below).

    Was this the case of your pack? Was this pack coming from a damaged car?

    Post from teslamotorsclub:
    “Our still anecdotal (ie. limited data, still early, etc.) suggests that under impact (unclear whether light or hard, when in X, Y or Z axis) the revamped voltage sensor hardnesses are subject to detachment. unclear if that’s simply coincidence, or combination of manufacturing/design defect and impact, or impact alone. but we are seeing it. again, still early.”

    1. That is missleading feedback. We have opened packs with heavy crash and sense wiring was still intact. And if anyone with common sense and skills just checked our picture of failed 100 pack sense wiring you can see it is streched due thermal expansion of module it self. This is already documented problem worldwide and inside tesla fleet tracking mothership data.

Leave a Reply

Your email address will not be published. Required fields are marked *


This site uses Akismet to reduce spam. Learn how your comment data is processed.