SLUUA65E april 2014 – june 2023 BQ28Z610
The Fast QMax Update Conditions are very similar to the QMax Update Conditions with the following differences:
The differences in requirements allow the Fast QMax feature to have a QMax update at the end of discharge (given one OCV reading is already available and discharge < 10% RSOC) without a longer relax time after a discharge event. The Temperature, Delta Capacity, Voltage, and Offset Error requirements for a QMax update are still required for the Fast QMax update.
This feature is particularly useful for reducing production QMax learning cycle time or for an application that is mostly in CHARGE or DISCHARGE state with infrequent relaxation. Setting IT Gauging Configuration[FAST_QMax_LRN] = 1 enables Fast QMax during production learning only (that is, Update Status = 6).
The DOD is taken for QMax at a high state-of-charge, then during discharge when at the steep portion of the voltage curve (85–90% DOD). This allows a good estimation of DOD again. This DOD estimation during discharge is used to update QMax immediately instead of needing a rest period first. The actual update to QMax happens when the discharge stops after verifying that no conditions were present that would cause the QMax update to fail. The BQ28Z610 has an option to have DOD@EOC be valid for QMax updates, which means it is possible to update QMax with no rest periods at all (by having a charge termination followed by a full discharge); however, this is only recommended for certain new chemistries. Fast QMax can be enabled in either LEARN mode (FAST_QMax_LRN) or FIELD mode (FAST_QMax_FLD). The LEARN mode flag means Fast QMax is only enabled in IT state “06”, and will be disabled once 0E is reached. FIELD mode is enabled in both “06” and “0E” states.