Edit: We published another minor bug fix as V_0.222_BETA on July 5.

We have published the first firmware update for Pathfinder BMSs as V_0.221_BETA. All Pathfinders are set to load “STABLE” updates only, so if you haven’t already, please set your BMS to load “BETA” updates, and connect to WiFi.

If you prefer to update offline with the UF2 method, you can find the new file here: https://github.com/OverkillSolarLLC/UF2

The datasheet has been updated to go along with the new firmware: Pathfinder BMS datasheet PDF

Recovery Mode is here!

There are a lot of bug fixes in this release, and some new features including the addition of Recovery Mode. This feature allows you to manually start up the system after a discharge cutoff by enabling the predischarge circuit from the BMS controls. To use it, navigate to “Recovery Mode” on the screen, and hold the OK button. The screen will display the system voltage and you can easily see when your charger engages by the bump in voltage. If the loads on the system are still too high for the predischarge circuit, you will see the red “overload” LED on the main board light up. In that case you will have to shed loads from the system or connect a “dumb” power supply.

This update also includes improvements to the BQ34Z100 Learning Cycle, MQTT bug fixes, and other miscellaneous bug fixes.

Your feedback is valuable! Please send an email to Support@OverkillSolar.com if you have anything to say about this update, good or bad. Remember, if you ever need to roll back an update, or if you rejected an update and changed your mind, all versions are available in UF2 format forever.

Pathfinder BMS firmware change log July 3 2025

V_0.222_BETA

• Bug fix: Prevent learning cycle instructions from repeating after the cycle is finished.
• Added Learning cycle “Stage” to non-volatile storage. When the BMS reboots after this update, the stage variable will be lost, but thereafter it will be retained. This does not interrupt the Learning cycle but it will interrupt the sequencing of the on-screen instructions if a learning cycle is already active.

V_0.221_BETA

• Bug fix: disabling radio power freezes the user interface
• Don’t auto-start the Learning cycle. Added Start Learning Cycle button to Learning Cycle screen.
• Changed Charge Overcurrent Recovery parameter default to -200mA from 0mA to prevent rapid cycling of a charge overcurrent fault. (not user adjustable)
• Bug fix: changing protection parameters to overlap an existing fault condition caused the BQ76952 to crash. Added a partial reset of the BQ76952 after every parameter change.

V_0.215_BETA

Note: some BMSs were shipped with V_0.215_BETA, but the OTA and UF2 files were bumped up to V_0.221_BETA before publishing the update.

Learning cycle

• Adjusted learn cycle termination voltages to narrower range to accommodate moderate cell mismatch. These parameters are still non adjustable in the field.
• Added Learning Cycle Reset function to the RESET screen. This resets the BQ43Z100 and re-initializes the learning cycle. User parameters are not overwritten, but calibrations are erased. Null current calibration must be repeated after a learning cycle reset.
• Added a warning when changing design capacity after learning cycle is started. Once started, the Z100 learning cycle must be reset before capacity can be changed.
• Bug fix: Energy and current not scaled correctly for the learning cycle. This caused the reported measured capacity to be 5x too high. Scale factor for energy and current is now calculated when setting Design Energy. Current resolution will now change depending on the scale factor.
• Improved on screen instructions for learning cycle.

MQTT

• Add MQTT status screen.
• Bug fix: MQTT was not indexing active cells if less than 16. High/low cell numbers were off by 1.
• Bug fix: Cell delta incorrectly formatted for MQTT
• Limit the retry rate for a disconnected MQTT broker to 5 minutes, or 5 seconds if the user cancels the warning popup.
• Bug fix: MQTT broker disconnecting may cause OTA to fail due to memory leak. MQTT not properly handling broker disconnect events.
• Bug fix: MQTT leaking memory during connect attempts if radio power is off.
• Bug fix: MQTT power was displaying current instead of power due to wrong data variable- linked the correct data source.

Recovery Mode

• Added Recovery Mode screen- Recovery mode is manual operation only, hold the OK button to engage the output via the predischarge circuit.

Misc

• Added indicators around cell voltage on OLED cell voltage screens to show which cell is balancing.
• Added function to load alpha OTA with secret code (UP-DN-L-R). Customers should not use this function unless asked to test a specific alpha build.
• Display RemainingCapacity on SOH screen.
• Bug fix: Idle calibration routine was overshooting and not getting fresh data during automatic calibration.
• Bug fix: Wifi scan failed if radio power disabled. Added a warning and prevent starting the scan.
• Bug fix: Antenna light sometimes stuck on when radio power is disabled.
• Bug fix: restart BLE advertising after cycling radio power.