SLUUCA6 October 2021 BQ27Z746
SHELF mode operates the same as SHIP mode with a minimized amount of measurements and firmware processing. However, device power consumption in SHELF mode is reduced from SHIP mode by turning off the CHG and DSG FETs and hardware protector (all hardware-based protections and IWAKE). Due to the FETs being off in SHELF mode, the system is not powered without a charger attached, so the exit conditions are different from SHIP mode and the FET control logic is not performed.
In SHELF mode, the device measures voltage and temperature very infrequently and at shorter ADC conversion times, and current is not measured or coulomb counted. Current is assumed to be and reported as 0 mA. Therefore, the device tracks the battery's state-of-charge from OCVs. The measurements performed each interval are:
Firmware processing is minimized by reducing the number of calculations. Some calculations are performed less frequently: only after voltage and temperature are measured. These less frequent calculations include updating firmware-based protections, lifetime data, and the voltage and temperature range of the advanced charge algorithm. Other calculations, such as updating RemainingCapacity() and FullChargeCapacity, are not performed at all with the assumption the system is off and will not communicate with the gauge.
SHELF mode is entered based on voltage through SLEEP or SHIP or by command through NORMAL or SLEEP. Exit from this mode is through command, voltage at the PACK terminal > VStartup–, or the ENAB pin being pulled low. The latter two conditions are shared with SHUTDOWN and only checked Shelf Exit Holdoff seconds after entering SHELF mode to allow pin voltages to settle once the DSG and CHG FETs turn off.
Status | Condition | Action |
---|---|---|
Activate | (OperationStatusA()[SLEEP] =
1 AND Voltage() < Shelf Voltage Threshold for Shelf Voltage Delay) OR (OperationStatusB()[SHELFM] = 1 for Shelf Command Delay AND |Current()| ≤ Sleep Current) |
OperationStatusA()[SHELF] =
1 The device enters RELAX mode. Current() = 0 mA, AverageCurrent() = 0 mA The device wakes up every Shelf Measure Time to measure voltage and temperature.(1) The device does NOT coulomb count or measure current. Turn off the CHG and DSG FETs. Turn off the protector (all hardware-based protections and IWAKE). |
Exit | (Voltage() ≥ Shelf
Voltage Threshold AND OperationStatusB()[SHELFM] = 0) OR (OperationStatusB()[SHELFM] = 1 AND MAC ShelfDisable() received) OR (Time in SHELF mode ≥ Shelf Exit Holdoff AND (Voltage at PACK terminal > VStartup– OR ENAB pin pulled low)) |
OperationStatusA()[SHELF] =
0 OperationStatusB()[SHELFM] = 0 Return to NORMAL mode |
If the gauge is UNSEALED and the MAC ShelfEnable() command is sent twice in a row, the gauge enters SHELF immediately and skips the normal delay sequence.
The configuration options for SHELF are in the following data flash.
Class | Subclass | Name | Type | Min | Max | Default | Unit | Description |
---|---|---|---|---|---|---|---|---|
Power | Shelf | Shelf Voltage Threshold | I2 | 0 | 32767 | 2200 | mV | Cell based SHELF voltage trip threshold |
Power | Shelf | Shelf Voltage Delay | U2 | 0 | 255 | 10 | s | Cell based SHELF voltage trip delay |
Power | Shelf | Shelf Measure Time | U1 | 1 | 30 | 30 | s | Determines the wake interval to measure voltage and temperature in SHELF mode |
Power | Shelf | Shelf Command Delay | U1 | 0 | 255 | 10 | s | Delay time to enter SHELF mode after MAC ShelfEnable() is received. The device takes an additional 1-2 seconds to enter SHELF mode for command processing |
Power | Shelf | Shelf Exit Holdoff | U1 | 1 | 255 | 10 | s | Holdoff time after entering SHELF mode to check the PACK and ENAB pin exit conditions |