Sometimes, a major issue may be just right in front of your eyes and go unnoticed until someone sounds the alarm. That is what Mario Zelaya did when he shared that his 2013 Tesla Model S failed due to a design flaw: the AC drain hose, which drops water right over the battery pack. Jason Hughes confirmed the problem and added that “deteriorated side rail vents” also allow moisture to invade the battery packs. Gruber Motor Company made a video about that nine months ago.
Pete Gruber had already warned that Teslas in coastal areas could face battery pack corrosion issues, but we now know this may only accelerate the problem. The real cause is having water drop on top of the battery pack all the time, something that is almost unbelievable that the engineers involved with the project did not anticipate.
Cristina Balan was called the CAD Fairy when she worked for Tesla on the battery pack project. In Tesla’s response to the defamation lawsuit she filed against the company, the EV maker wrote that “her work was at the heart of innovation at Tesla.” It also said that, while she worked there, she invented a new way to use CATIA, a design tool that shortened design time from hours to minutes.” According to Tesla, Balan “was the first person in the world to develop this methodology, one that still uses to date.” We had no one better to ask about the problem.
Photo: Gruber Motors
The engineer told us she was only involved with module design, so she could not tell us who decided to place an AC drain hose dripping over the battery pack. Anyway, she remembers pretty well who the two leading executives dealing with the component design were: Peter Rawlinson and Drew Baglino, Senior Vice President of Powertrain and Energy Engineering at Tesla.
Baglino’s LinkedIn page says he was the “Model S Powertrain Architect, Principal System Design Engineer” from July 2009 until July 2013. He describes his responsibilities as leading “a small team focusing on powertrain modeling, analysis, optimization, and requirements definition for the battery.” Regarding Rawlinson, the current Lucid Motors CEO was Tesla’s chief engineer: nothing in the Model S could have been made without his approval.
Photo: Gruber Motors
That means that none of these men realized that having a continuous water source dripping over a steel component could only qualify as a bad engineering decision. The side rail vents deteriorating to the point of allowing moisture ingress were the result of issues with either design or manufacturing. We’ll investigate whether it is the former, the latter, or a combination of both.
What matters to this story is checking how unfortunate it is to have the AC drain hose over the battery pack. In Zelaya’s case, the water made the steel fuse box cover in his Model S rust. As a consequence, moisture invaded the compartment. Multiple measures that could avoid that come to mind. Moving the AC drain hose somewhere else, replacing the cover of the fuse box with something made with a material that doesn't rust, or better insulating the battery pack are examples off the top of our heads.
Photo: Gruber Motors
The battery pack in Zelaya’s Model S had stains in the areas where water poured and dried. In the 2014 Model S that Gruber Motors tried to fix, there was still water inside the fuse box, battery pack, battery modules, and under the fire blanket on the battery pack. Some cells presented rust. The bolts underneath the fire blanket are also severely corroded, making Pete Gruber suspect water may have invaded the battery pack due to that. That would make these bolts another failure element apart from the AC drain hose and the side rail vents. Would that be a surprise at this point?
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