Tesla Model 3/Y Owners Hit With BMS_a079 Error Indicating the High-Voltage Battery Is Gone

Tesla Model 3/Y owners hit with BMS_a079 error 6 photos
Photo: Kolton Constant via Facebook
Tesla Model 3/Y owners hit with BMS_a079 errorTesla Model 3/Y owners hit with BMS_a079 errorTesla Model 3/Y owners hit with BMS_a079 errorTesla Model 3/Y owners hit with BMS_a079 errorTesla Model 3/Y owners hit with BMS_a079 error
Although studies showed that EV battery failures are rare, many Tesla Model 3 and Model Y owners complained that their car batteries died just outside the warranty period. The problem occurred suddenly with a BMS_a079 error code, indicating that some of the cells in the battery pack were faulty. The only remedy is a battery replacement, which might be expensive if the warranty has expired.
One of the biggest fears concerning EV owners is a damaged high-voltage battery. The reason is the high replacement costs, which can ruin anyone's budget if the warranty doesn't cover it. Thankfully, Tesla offers a comprehensive battery warranty for eight years or 120,000 miles (100,000 miles for Model 3/Y RWD), whichever happens first. This is enough for most people, although those who drive a lot might beg to differ.

Recent studies showed that battery failures are rare, especially on newer electric vehicles. However, when they occur, only a battery replacement solves the issue. This is very expensive, even when the replacement pack is a refurbished part. The most affordable are remanufactured packs from third-party vendors. In the case of the Model 3, these packs start at about $7,000, including installation, for a 180-mile pack. Replacement packs from Tesla could cost at least twice as much, depending on the model.

The good news is that most of these faulty batteries are replaced under warranty. The eight-year period means that many EVs produced in 2016 are still covered. That is, if they have not exceeded the mileage. This is important because it appears that there's an epidemic of Tesla Model 3 and Model Y owners complaining that their EV batteries died.

According to many social media and forum reports, battery failures occur out of the blue when a BMS_a079 error code is displayed on the infotainment screen. The message description is brief: "Unable to charge - Maximum charge level reached," instructing the owner to schedule service. When they did, they discovered that this was caused by an imbalance in the battery pack that could only be solved by replacing the high-voltage battery.

Many complained that the failure occurred soon after reaching the warranty's mileage limit. This made some people think that Tesla ensured the message was delayed until the warranty expired. However, this is not the case, as most of those with the failed battery had theirs replaced under warranty. A quick search reveals that many unlucky Model 3 and Model Y owners drove a 2021 model, although some have newer models. A 4680 Model Y (2023 model) and a brand-new 2023 Model Y Performance were among those with BMS_a079 error codes, so the cell type and manufacturing year are less important.

At some point, one affected owner shared on Reddit that he could make the error message disappear by disconnecting the high-voltage battery harness under the rear seats for a few minutes. Although this worked in their case, other owners reported that the error message returned. Just like Model S owners affected by the BMS_u029 error, hiding the error doesn't solve the problem, which is caused by faulty battery cells inside the battery pack.

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About the author: Cristian Agatie
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After his childhood dream of becoming a "tractor operator" didn't pan out, Cristian turned to journalism, first in print and later moving to online media. His top interests are electric vehicles and new energy solutions.
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