SLUAAL7 September 2022 BQ35100
After performing a complete discharge of the primary cell and logging the resistance, the EOS parameters can be configured.
The only parameter that needs to be updated for initial EOS learning is the New Batt R Scale Delay, this needs to be set to a value after the passivisation layer is expected to be gone. The passivisation layer can be seen as the initial resistance measurement being higher than expected, and then decreasing after subsequent pulses. Once resistance stops decreasing and is flat, the passivisation layer has been removed.
| Class | Subclass | Name | Type | Size | Min Value | Max Value | Default Value | Unit |
|---|---|---|---|---|---|---|---|---|
| EOS Data | Values | New batt R scale delay | Unsigned Integer | 1 | 0 | 255 | 2 | Readings |
| EOS Data | Values | R Table Scale | Integer | 2 | -1 | -1 | -1 | – |
| EOS Data | Values | R Table Scale Update Flag | Hex | 1 | 0×00 | 0×ff | 0×ff | – |
After the initial learning is setup, the most important value to configure from the resistance data is the EOS Trend Detection this determines when the gauge sets the [EOS] flag by comparing the Short Trend Average and Long Trend Average.
| Class | Subclass | Name | Type | Size | Min Value | Max Value | Default Value | Unit |
|---|---|---|---|---|---|---|---|---|
| EOS Data | Values | R short trend filter | Unsigned Int | 1 | 1 | 255 | 251 | – |
| EOS Data | Values | R long trend filter | Unsigned Int | 1 | 1 | 255 | 253 | – |
| EOS Data | Values | EOS trend detection | Unsigned Int | 1 | 1 | 100 | 20 | – |
| EOS Data | Values | EOS detection pulse count | Unsigned Int | 2 | 1 | 20000 | 120 | – |
| EOS Data | Values | EOS detection pulse count Thrhd | Unsigned Int | 2 | 1 | 20000 | 120 | – |
| EOS Data | Values | Short trend average | Unsigned Int | 4 | 1 | 8355712 | 0 | – |
| EOS Data | Values | Long trend average | Unsigned Int | 4 | 1 | 8355712 | 0 | – |
To estimate the long and short filtered values we can use the following formulas from the TRM.
Short Trend Average = Impedance × 1/DF1 + Previous Impedance × (1–1/DF1)
Long Trend Average = Impedance × 1/DF2 + Previous Impedance × (1–1/DF2)
Where DF1 = 50, DF2 = 100, and Previous Impedance is the previously calculated Short Trend Average or Long Trend Average value.
To determine when the battery needs to be replaced, the following check is done which triggers the [EOS] flag.
Short Trend Average > Long Trend Average × (1 + EOS Trend Detection / 100)
When this occurs the [EOS] flag is set and cannot be cleared.
After the EOS flag is set, the battery needs to be replaced. The EOS alert indicates the battery is near end of life according to the customer settings of EOS Trend Detection and resistance increases.