SLUUCO9A April 2023 – November 2023 BQ28Z620
To avoid charging a pack that was depleted, the BQ28Z620 implements a new permanent fail for safety undervoltage (SUV). This feature can be enabled/disabled by a DF setting in Settings:Permanent Failure subclass.
Status | Condition | Action |
---|---|---|
Normal | All cell voltages in DAStatus1() > SUV:Threshold |
PFAlert()[SUV] = 0 BatteryStatus()[TDA] = 0 |
Alert | Any cell voltage in DAStatus1() ≤ SUV:Threshold |
PFAlert()[SUV] = 1 BatteryStatus()[TDA] = 1 |
Trip | Any cell voltage in DAStatus1() continuous ≤ SUV:Threshold for SUV:Delay duration |
PFAlert()[SUV] = 0 PFStatus()[SUV] = 1 BatteryStatus()[FD] = 1 |
Related data flash parameters for this feature are described below.
Class | Subclass | Name | Type | Min | Max | Default | Unit | Description |
---|---|---|---|---|---|---|---|---|
Permanent Fail | SUV | Threshold | I2 | 0 | 32767 | 1000 | mV | Threshold below which the permanent fail alert is triggered |
Permanent Fail | SUV | Delay | U1 | 0 | 255 | 5 | s | Delay until the permanent fail trip is triggered |
Settings | Permanent Fail | Enabled PF A[SUV] | hex | — | — | 0 | — | The SUV bit is added to allow enable/disable of this PF. |
When powering up from shutdown, the device first checks the cell voltages. If any cell voltage meets the Alert condition above (any cell voltage ≤ SUV:Threshold), then the FETs will be kept off until either the Alert condition is cleared (so all cell voltages > SUV:Threshold) or the SUV:Delay timer expires, at which point the SUV PF is triggered, and the FETs will remain off.
The gauge continues checking the SUV conditions regularly during operation and can generate the PF Alert or Trip if conditions warrant. For example, this may occur if the customer sets the SUV:Threshold higher than the level at which the gauge goes into shutdown, so the gauge first triggers the CUV protection, the discharge FET turns off, but the cells continue to self-discharge until they eventually fall below the SUV:Threshold.
The firmware and TRM changes include Section 15.3.4, a new SUV data flash Section 15.11.1, Chapter 16, and a new section for SUV Permanent Fail, Section 4.2.