Hi,
We were trying to test autonomous cell balancing on the BQ76942. Unfortunately, after configuring the registers and trying to enable autonomous cell balancing, we were unable to get autonomous cell balancing to start, although we were able to get host controlled balancing to commence for one second using the CB_ACTIVE_CELLS subcommand. The following are the settings and configurations we set to do the autonomous cell balancing:
- Set CELL_BALANCE_MAX_CELLS to 3
- Kept CELL_BALANCE_INTERVAL to 20s
- Changed MIN_CELL_TEMP to -128 degrees, and MAX_CELL_TEMP at default. Our external thermistors are used as cell temperature readings, and read room temperature (22 C). Internal die temp reads as 24 C.
- In the Balancing Config Register, CB_CHG, CB_RLX, and CB_SLP are all set high to allow balancing during those states.
- Both DSG_CURR_THRESH and CHG_CURR_THRESH are set to 30000 (30A, our userA are mA) to make sure we are in relaxed state for balance.
- Minimum Cell Voltage (Relax) is set to 0 volts.
- Cell Balance Min Delta (Relax) is set as default, 40 mV. Cell Balance Stop Delta (Relax) is set as 20 mV.
- The CB_SET_LVL() is set to 0V.
For our hardware setup, we have a power supply and a resistor network that imitates cells. Four cells are at 3.2V, one cell is at 0.8V, and the remaining five cells are at 3.0 V.
When evaluating conditions that could cause autonomous cell balancing to not start, I ensured that we had exited CFG_UPDATE mode, checked and verified that no protection alerts or faults were set, no permanent fails are enabled, and the device is not in DEEPSLEEP or SHUTDOWN mode.
Could you advise on what the issue might be regarding the autonomous balancing not starting? When reading with CB_ACTIVE_CELLS, the mask returns 0. Additionally, using the CBSTATUS1/2/3 commands all return 0, indicating balancing has not been active.
Thanks,
Ryan
