SLUUD50 October 2024 BQ27Z758
Cell swelling can occur when the cell temperature and cell voltage are above certain thresholds. In these situations, the charging voltage can be stepped down gradually until the cell temperature moves back down.
This scheme works (as shown in Figure 12-4) when enabled by setting [CS_CV] (default is cleared) in the Charging Configuration register. When the max cell voltage1..4 and cell temperature are above the Voltage Threshold and Temperature Threshold, respectively, for the period defined by Time Interval, then the charging voltage is stepped down by Delta Voltage. This step down continues until either the max cell voltage1..4 and cell temperature conditions go away (that is, cell swelling reduces) or the step down reaches Min CV.
The charging voltage reduction/degradation resulting from this feature is reset when exiting CHARGE mode.
This degradation works in conjunction with other degradation features; therefore, use with care.