Disclaimer
Working on vehicles, especially electric ones, carries significant risks. High-voltage systems in EVs can be particularly hazardous, and many skilled mechanics and DIY enthusiasts may not fully understand their dangers. The information provided here is purely for reference. Anyone using this guide assumes all risks and should adhere to all safety precautions.
Introduction
This guide focuses on the High Voltage (HV) Battery packs used in Tesla Model S and Model X vehicles from 2012 to 2020. It is structured into sections that are best navigated using a desktop browser. If your vehicle has recently stopped functioning and you suspect an issue with the HV battery, this resource aims to help you ask the right questions at a repair shop or assist with DIY repairs—if you have the necessary skills, time, and expertise.
When an HV battery fails, multiple error messages may appear on the vehicle’s screen. These errors often result from the 12V battery losing charge, as the HV battery stops supporting it. Many of these warnings are not directly related to the root cause. The initial goal is to keep the 12V battery operational long enough to collect error details and extract data using a tool like Scan My Tesla. Additionally, capturing photos of error messages, ideally from Service Mode, can aid in diagnosis. For troubleshooting, online forums and Tesla owner groups are valuable resources. This guide also provides a step-by-step approach for certain repairs. While it may be tempting to jump straight to specific sections, it is highly recommended to read everything before attempting any repairs, especially the safety instructions. preliminary things
Important Notes
Even if you do not intend to perform any repairs yourself, this information can still be beneficial. It can help you understand the process and ensure that any repair shop you choose follows the correct procedures. If you are considering purchasing a used Model S or Model X, this guide may help you make an informed decision about whether an older Tesla is right for you.
If you notice any inaccuracies or missing details in this guide, or if any section is unclear, feel free to reach out via the contact form for updates or corrections. If any images or information were mistakenly used without proper credit, please contact us so we can make the necessary adjustments. If you have expertise in any areas covered in this guide and would like to contribute, let’s discuss possible collaborations.
Scope of This Guide
This resource primarily covers the HV battery packs found in Tesla Model S and Model X vehicles manufactured between 2012 and 2020. Most examples and images reference the Version 1 packs (2012–2015), though much of the information also applies to Version 2 packs (2015–2020). Vehicles produced from 2021 onwards, as well as Tesla Model 3, Model Y, and Cybertruck, use different battery configurations with distinct connectors and specifications, which are beyond the scope of this guide.
If your Tesla has stopped working, it’s important to recognize that there are numerous potential causes beyond a failing HV battery. Many HV system issues can prevent the vehicle from operating, charging, or supporting the 12V system. Some of these issues are simpler and more cost-effective to resolve, but diagnosing and repairing them falls outside the scope of this document.
High Voltage Safety Considerations
Tesla’s HV battery packs operate at voltages high enough to be fatal. Unlike traditional automotive hazards—such as hot engine components or moving belts—electricity is invisible, silent, and can be lethal without warning. Understanding how the HV system functions is crucial before attempting any work. Simply removing a fuse does not make the system safe—many packs retain high voltage even with fuses removed.
This is not a minor electrical shock—it can be deadly. Exercise extreme caution and use proper safety equipment. Recommended resources include:
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Hybrid/Electric training – by DiagnoseDan YouTube Videos
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Hybrid and Electric Vehicle Personal Protective Equipment (PPE) and Tools – by Professor John Kelly at Weber Auto on YouTube
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Loss of Isolation Diagnostics – by Professor John Kelly at Weber Auto on YouTube
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Insulation Testing on Hybrid Vehicles – by Garage Gurus on YouTube
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The final report from the famous “Battelle Study” ordered by NTSHA (especially check the figures in chapter 5)
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Research on Electric Shock Prevention and First Aid for Electric Vehicles – paper @ Researchgate
Assessing Your DIY Skill Level
Removing an HV battery from a Tesla in a home garage with standard tools is relatively straightforward. However, reinstalling it requires greater care, and working with the pack itself introduces serious risks. These battery packs weigh roughly 1,000 pounds, and the vehicle must be properly secured on ramps or jack stands—any failure in stability can be dangerous.
Opening an HV battery pack safely and without damaging the lid is particularly challenging. Since replacement lids are not readily available, any damage can lead to complications. Once the lid is removed, the real HV risks begin.
Additionally, electric vehicle repairs often reach a ‘point of no return.’ If a traditional internal combustion engine (ICE) vehicle’s engine or transmission is removed but the repair cannot be completed, there are many repair shops that can step in, and selling the vehicle for parts is always an option. However, once an HV battery pack is disassembled, Tesla will no longer accept it as a trade-in for a replacement pack. If you damage or fail to repair the pack, you may find yourself stuck with an unusable vehicle and a hefty replacement cost—potentially increasing a $16,000 repair into a $26,000 problem.
Before starting, be realistic about your capabilities and the risks involved.
