SLUUCP8 June 2024 BQ41Z50
The BQ41Z50 device includes an extension of the elevated charge degradation function described in Section 4.19, which notifies the host when any cell voltage is ≥ the specified EVTM voltage threshold and the battery spends a prolonged period of time under the specified EVTM temperature range. This feature provide a method to reduce battery aging by providing multiple degradation steps to reduce ChargingVoltage() before the [ERETM_ACTIVE] flag is set and the device enters Elevated RSOC and Temperature Mode. When [ERETM_MODE] = 1, this feature can be enabled by setting [EVTM_EXT_MODE] = 1.
As shown in Table 4-4, lifetimes counters are incremented once every hour to track the time under each of the 3 temperature and 3 voltage ranges. The lifetimes counters are held unchanged at its present value for periods when the cell voltage or temperature is outside of the specified ranges for the corresponding lifetimes counter.
| Lifetimes Counter | Temperature Range | Temperature Condition |
|---|---|---|
| Accumulated EVLTM Time | EVLTM | EVTM Temperature Low Threshold ≤ temperature < EVTM Temperature Mid Threshold and cell voltage ≥ EVTM Voltage High Threshold |
| Accumulated EVMTM Time | EVMTM | EVTM Temperature Mid Threshold + EVTM Temperature Threshold Hysteresis ≤ temperature < EVTM Temperature High Threshold and cell voltage ≥ EVTM Voltage Mid Threshold |
| Accumulated EVHTM Time | EVHTM | EVTM Temperature High Threshold + EVTM Temperature Threshold Hysteresis ≤ temperature and cell voltage ≥ EVTM Voltage Low Threshold |
Under each temperature range, ChargingVoltage() can be reduced down by a programmable delta voltage if the value of the accumulated time counter falls between the corresponding time ranges as shown in Table 4-5. The bits in the EVTM ACTIVE register are asserted to indicate which degradation conditions which are met. Once the device enters CHARGE mode, the corresponding delta degradation will be applied to the ChargingVoltage(), and the corresponding bit in the EVTM Degrade register will be asserted.
| Degradation Steps | Temperature Range = EVLTM | Temperature Range = EVMTM | Temperature Range = EVHTM | |||
|---|---|---|---|---|---|---|
| Time Range | ChargingVoltage() Degradation | Time Range | ChargingVoltage() Degradation | Time Range | ChargingVoltage() Degradation | |
| 1 | EVLTM TTH1 ≤ Accumulated EVLTM Time < EVLTM TTH2 | ChargingVoltage() - EVLTM CV Delta1 | EVMTM TTH1 ≤ Accumulated EVMTM Time < EVMTM TTH2 | ChargingVoltage() - EVMTM CV Delta1 | EVHTM TTH1 ≤ Accumulated EVHTM Time < EVHTM TTH2 | ChargingVoltage() - EVHTM CV Delta1 |
| 2 | EVLTM TTH2 ≤ Accumulated EVLTM Time < EVLTM TTH3 | ChargingVoltage() - EVLTM CV Delta2 | EVMTM TTH2 ≤ Accumulated EVMTM Time < EVMTM TTH3 | ChargingVoltage() - EVMTM CV Delta2 | EVHTM TTH2 ≤ Accumulated EVHTM Time < EVHTM TTH3 | ChargingVoltage() - EVHTM CV Delta2 |
| 3 | EVLTM TTH3 ≤ Accumulated EVLTM Time < EVLTM TTH4 | ChargingVoltage() - EVLTM CV Delta3 | EVMTM TTH1 ≤ Accumulated EVMTM Time < EVMTM TTH2 | ChargingVoltage() - EVMTM CV Delta3 | EVHTM TTH3 ≤ Accumulated EVHTM Time < EVHTM TTH4 | ChargingVoltage() - EVHTM CV Delta3 |
| 4 | EVLTM TTH4 ≤ Accumulated EVLTM Time < EVLTM TTH5 | ChargingVoltage() - EVLTM CV Delta4 | EVMTM TTH4 ≤ Accumulated EVMTM Time < EVMTM TTH5 | ChargingVoltage() - EVMTM CV Delta4 | EVHTM TTH4 ≤ Accumulated EVHTM Time < EVHTM TTH5 | ChargingVoltage() - EVHTM CV Delta4 |
| 5 | EVLTM TTH5 ≤ Accumulated EVLTM Time | ChargingVoltage() - EVLTM CV Delta5 | EVMTM TTH5 ≤ Accumulated EVMTM Time | ChargingVoltage() - EVMTM CV Delta5 | EVHTM TTH5 ≤ Accumulated EVHTM Time | ChargingVoltage() - EVHTM CV Delta5 |