SLUUC54C February 2020 – March 2024 BQ27Z558 , BQ27Z561 , BQ27Z561-R2
The impedance is different across different DOD states. The cell has 15 Ra grid points representing the impedance from 0%–100% DOD. In general, the Ra table is updated during discharge. The GaugingStatus()[RX] flag will toggle when the Ra grid point is updated. The Ra update is disabled if any of the following conditions are met. The GaugingStatus()[RDIS] is set to indicate the Ra update is disabled.
A valid OCV reading during RELAX mode or a Fast QMax update without an OCV read will clear the [RDIS] flag.
The configuration options related to Ra table updates are in the following data flash.
| Class | Subclass | Name | Type | Min | Max | Default | Unit | Description |
|---|---|---|---|---|---|---|---|---|
| Gas Gauging | IT Cfg | Resistance Parameter Filter | U2 | 1 | 65535 | 65142 | — | This is the filter coefficient on voltage, current, and temperature for resistance updates. Reducing this filter setting can improve low temperature performance at high rates. Examining the Term Voltage Delta setting and Fast Scale Start SOC should be done prior to adjusting this parameter when trying to improve the RSOC performance. The following is the formula to convert the DF setting into actual filter time constant: Filter time constant = [1/(1 – (DF_Value /65536))] – 1. |
| Gas Gauging | IT Cfg | Max Charge Current % | U1 | 0 | 100 | 10 | % | If AverageCurrent() changes by more than this threshold from the previous resistance measurement to the present, the present resistance measurement and Ra scale update are not used. This protects resistance measurements from voltage transients after step changes in current, especially transitions to relaxation. |
| Gas Gauging | IT Cfg | Resistance Update Voltage | I2 | 0 | 32767 | 50 | mV | The difference between the open circuit voltage based on DOD and the measured voltage is estimated as the IR drop. If this IR drop is greater than Resistance Update Voltage, then the resistance calculation is allowed. This can be helpful in applications with small battery packs and large resistances that do not meet the C/10 minimum current requirement for resistance updates. |
| Gas Gauging | IT Cfg | Ra Filter | U2 | 0 | 999 | 800 | 0.1% | Filter value used in Ra updates that specifies what percentage of the Ra update is from the new value (100%—setting) versus the old value (setting). The recommended setting is 80% if fast resistance scaling is enabled. Otherwise, the setting should be 50% as the default. |
| Gas Gauging | IT Cfg | Ra Max Delta | U1 | 0 | 255 | 15 | % of Design Resistance | Maximum value of allowed Ra change |
| Gas Gauging | IT Cfg | Design Resistance | I2 | 1 | 32767 | 90 | mΩ | Cell resistance at grid point 4. Automatically updated during learning when Update Status is set by the gauge to 06 and 0E. To automatically update again, set Update Status to 04. Design Resistance could be set manually when Update Status = 0E. |