SLUUCP8 June 2024 BQ41Z50
The BQ41Z50 includes a monitoring scheme that notifies the host when the battery spends a prolonged period of time at an elevated RSOC level with or without respect to temperature, depending on the configuration. The temperature used for this feature is the maximum temperature source configured for cell temperature. This feature uses the counter Accumulated ERM Time that is incremented once for every hour that RelativeStateOfCharge() ≥ ERM RSoC Threshold. For periods where ERM Reset RSoC Threshold < RelativeStateOfCharge() < ERM RSoC Threshold, the Accumulated ERM Time is held unchanged at its present value.
When the Accumulated ERM Time ≥ ERM Time Threshold, an [ERM] flag is set, signaling to the host that ELEVATED RSOC mode has been entered.
Recovery occurs if RelativeStateOfCharge() < ERM Reset RSoC Threshold, at which point Accumulated ERM Time and [ERM] are cleared to their default state of 0.
To use voltage-based thresholds (ERM Voltage Threshold and ERM Reset Voltage Threshold) in place of RSOC-based ones for this mode, the configuration bit [ERM_MODE] must be set (the default value is 0).
The separate counter Accumulated ERETM Time is used to track time at the elevated temperature, as well as RelativeStateOfCharge(), and can be used to reduce ChargingVoltage(). This counter is incremented once for every hour that RelativeStateOfCharge() ≥ ERETM RSoC Threshold, and ERETM Temperature Threshold < temperature < ERETM Temperature Max Threshold. For periods where RelativeStateOfCharge() < ERETM RSoC Threshold or RelativeStateOfCharge() ≥ ERETM RSoC Threshold and temperature < ERETM Temperature Threshold, the Accumulated ERETM Time is held unchanged at its present value.
When the Accumulated ERETM Time ≥ ERETM Time Threshold, an [ERETM_ACTIVE] flag is set, signaling to the host that Elevated RSOC and Temperature Mode has been entered, and ChargingVoltage() for all temperature ranges is permanently set to ERETM Charging Voltage without further degradation, starting from the next charge cycle along with the flag [ERETM_DEGRADE] setting.
If at any point RelativeStateOfCharge() > ERETM RSoC Threshold and temperature > ERETM Temperature Max Threshold, the [ERETM_ACTIVE] flag is immediately set, bypassing the counter threshold. Once active, exit from this mode is prohibited and the gauge stays in this mode for the remaining life of the pack. This ERETM Temperature Max Threshold related trigger can be disabled by clearing the [ERETM_MAX_T] configuration bit.
Since Elevated RSOC and Temperature Mode supersedes ELEVATED RSOC mode, the latter and its associated [ERM] flag are deactivated once the former is triggered.
To use voltage-based thresholds (ERETM Voltage Threshold) in place of RelativeStateOfCharge()-based ones for this mode, the configuration bit [ERETM_MODE] must be set (default is cleared).
To disable each mode, clear its respective enable bit ([ERM TIME] and/or [ERETM TIME]).