SLUUCA6 October 2021 BQ27Z746
The BQ27Z746 device implements an updated version of the battery state-of-health (SOH), which is reported by the StateOfHealth() command. In the previous version (in the BQ27Z746 device), the StateOfHealth() was calculated using a special 25°C version of FullChargeCapacity() as a fraction of Design Capacity. However, this calculation still included some parameters that were updated during operation based on the loading and use of the battery, separate from the battery status itself. This could lead to varying calculations of state-of-health for the same battery, depending on how the battery was used in the system. The updated version of StateOfHealth() addresses this by calculating a special FCC_SOH(), with the initial ambient temperature fixed at 25°C, using a current load specified by SOH Load Rate, and using the thermal model parameters, SOH Temp a and SOH Temp k.
The SOH Load Rate can be set to the typical current of the application, and it is specified in units of hour-rate (that is, Design Capacity / SOH Load Rate will be the current used for the SOH simulation). The SOH Temp a and SOH Temp k can be set to expected values for the system during operation. These data flash settings are used only for the StateOfHealth() calculation. The SOH full charge capacity is updated whenever QMax or the impedance table is updated. Because this implementation removes the variation of load current, temperature, and learned parameters, it is a better representation of the battery's state-of-health. The SOH full charge capacity is available on the MAC command FCC_SOH().
The configuration options for state-of-health (SOH) are in the following data flash.
Class | Subclass | Name | Type | Min | Max | Default | Unit | Description |
---|---|---|---|---|---|---|---|---|
Gas Gauging | SoH | SOH Load Rate | U1 | 1 | 255 | 50 | 0.1 Hr rate | Rate used in SOH simulation |
Advanced Charge Algorithm | Rec Temp Charging | Voltage | I2 | 0 | 32767 | 4400 | mV | Constant value for charge terminate voltage for the SOH calculation only |
Gas Gauging | State | SOH Temp k | I2 | 0 | 32767 | 1 | 0.1°C/ 256 cW | Thermal model temperature factor for SOH |
Gas Gauging | State | SOH Temp a | I2 | 0 | 32767 | 1000 | s | Thermal model temperature factor for SOH |
Gas Gauging | It Cfg | Min Delta Voltage | I2 | –32768 | 32767 | 0 | mV | Constant added to terminate voltage for the SOH simulation |