SLUUC54C February 2020 – March 2024 BQ27Z558 , BQ27Z561 , BQ27Z561-R2
When enabled with IT Gauging Configuration[RSOC_CONV] = 1, fast resistance scaling becomes active once one of the following is true:
For most applications, the default values of Term Voltage Delta and Fast Scale Start SOC are recommended. It is typically best to keep Term Voltage + Term Voltage Delta around 3.2 V–3.5 V, the knee of the discharge curve, for most battery applications.
Once active, every 30 seconds the algorithm calculates a new cell resistance scale as (Rnew / Rold) × 1000, where Rnew is the most recent measured cell resistance and Rold is the interpolated cell resistance at the present DOD. The raw scale is reported on Cell 1 RaScale. After a scale is calculated, an IT simulation is triggered to utilize the new resistance information. In addition, the scale is used for ambient temperature prediction (if enabled).
As a safeguard, the scale is limited to a minimum of 200 and a maximum of 5000 when applied, but Cell 1 RaScale maintains the raw scale. For clarity, a scale of 200 corresponds to 0.2 (reducing cell resistance) and 5000 corresponds to 5.0 (increasing cell resistance).