Our team’s own Dr.EV development vehicle has recently shown the first signs of the BMS a079 phenomenon.

Although we have analyzed numerous user datasets and real-world cases, this is the first time we have personally observed the same issue on our own vehicle. This gives us a valuable opportunity to study the problem not only from the developer’s perspective but also as an actual owner experiencing it firsthand.

To share some background: the vehicle was purchased used in June of last year with about 120,000 km. It has mainly been used for development, and the annual mileage is relatively low, around 5,000 km or less. When we bought the car, there was no practical way to assess the battery condition. After we began developing Dr.EV, our pack-level analysis indicated that degradation was already significant. At that time we did not fully understand the existence or frequency of the BMS a079 issue and assumed such cases were rare.

For reference, we are not a company with enough capital to own multiple test vehicles. Therefore, we have rarely conducted experiments that intentionally accelerate battery degradation. Unless for specific testing purposes, we usually keep the SOC range narrow and mainly use slow charging.

In the Dr.EV app’s Statistics view, we can see that despite similar charging patterns, the average cell deviation increased sharply within a single day.

In the Dr.EV Charging Session graphs, the cell-voltage spread expands abruptly overnight, which cannot be explained by normal aging.

As many of you already know, BMS a079 is not caused by natural cell degradation. It aligns with one of the mechanisms we discussed in our YouTube analysis. This pattern has been observed in user data, and now it has been reproduced in our own vehicle with the same signatures.

We are also observing a widening gap between Tesla’s displayed driving range and Dr.EV’s estimated range. We expect that the moment Tesla’s indicated range drops suddenly will likely coincide with the vehicle triggering the BMS a079 alert.

Fortunately, our car remains within its warranty period, with about two and a half years or roughly 40,000 km left, so no immediate action is required.

We will closely monitor pack temperature and overall stability due to the potential risk of thermal runaway.

If the BMS a079 fault is officially triggered, we will document and share Tesla’s response, including the replacement pack configuration and how it compares with the original. In parallel, we plan controlled experiments using Dr.EV measurements to either delay the onset or intentionally accelerate it, in order to better understand the underlying mechanism.