Editing Talk:Battery firmware lockout (section)

== On Texas Instruments BQ-series BMS ==

This type of BMSes is the most common type used on laptop computers.

Unlike the BMS in power tools that you can dump the firmware, the Texas Instruments BQ series BMS has something like "a chip within a chip", similar to Intel Management Engine or fTPM.

I learned from some friends who worked with power electronics. The BQ series needs password to access the internal memory. Unfortunately, the "Permanent Fail" is gated the same "height" of the "wall" as flashing firmware. If you know the password you can read and even write (both official and custom) firmware, if you don't know the password you can't even clear the PF error code. 

The BMS sends the battery's current status like the voltage, current, temperature, cycle count and the limitations like charge max voltage/current, discharge min voltage/max current, etc, to the device. It's know that some computer models use different battery packs, the EC supplies the correct voltage and current to the battery because the BMS tells these values to the EC. These messages are not encrypted and are read by embedded controller (EC) on the computer's motherboard.

Thus, we can technically build our own FOSS BMS using the same way of communication with the EC, without any "lockout" logic, or we can just buy a BQ chip from TI, use the official firmware but without setting a custom password. If the "community driven" custom BMS gains traction and reaches mass production, we can solve the "battery firmware lockout" once and for all.

The reason why few people talk about it, I think, is the "baseline" reliability difference. The reliability of a product depends on the least reliable part, so laptop batteries have to be very reliable. As a result, they don't fail randomly. Given the high quality standard, non-OEM battery manufacturers and independent repair technicians can rarely reach the reliability standard of the original ones. Therefore there's low incentive for those people to find a reliable way of unbricking the BMS. [[User:Charlie 6|Charlie 6]] ([[User talk:Charlie 6|talk]]) 13:13, 17 September 2025 (UTC)