Dear Texas Instruments team,
I'm a student at a federal higher technical educational institution of electronics in Austria. I'm working on a diploma project in a small team. We develop a prototype of a mobile Power supply for notebooks which works with batteries, accumulators or fuel cells. The battery pack require a Battery Management System. We have already developed a BMS circuit for the bq77910A IC.
Now we have a problem with the balancing algorithm. According to the datasheet, the IC will balance the cell with the highest voltage first.
We have been testing the cell balancing function of the BQ77910A. I have included a graph below showing how the balancing works. I also included the EEPROM registers.
I could not find a tolerance specification in the data sheet for the part. I understand the part compares all the cells and balances the highest cell, for dwell time then checks again. But in our case the IC balances also the lowest cell. This is unexplainable for us, because we have no influences to the balancing algorithm. This problem occurs by the EVM board as well by our own circuit.