Hello,
I have problems with the standard internal balancing configuration of the TI BQ40Z50.
I'm using BQ40z50-R1 Firmware, with 100 Ohm resistors on the circuit. The circuit is adapted from the EVM-Ciruit. The battery is a 4S1P with Samsung INR-18650-29E. The flags for Cell Balancing [CB] and Cell Balancing at Rest [CBR] are enabled (=1). OCVFR Bit is disabled (=0).
As shown on the attached image after a fully charged termination the cell voltages drop down and the device starts with internal balancing. Cell 1 is the one with the lowest voltage. Balancing correctly starts to decrease the voltage of cell 2, 3 and 4. Although cell Voltage 3 has droped down to cell voltage 1 the balancing continues. Similar happens to cell voltage 2. Annotation: the voltage drop at time ~50000 is caused by a 3A discharge.
I would have expected a balancing of the higher cell voltages down to the lowest cell voltage, as described in the TRM.
1) What is the reason for this behaviour? How can i get it under control?
2) In firmware BQ40z50-R1 the [CBM]-Flag is RSVD. I assume it is set to 1 permanently. So, the balancing should switch from cell to cell and not balance several cells at the same time? The image shows contemporaneous balancing of several cells, doesn't it?
Thanks for reply,
Simon
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