DISCHARGE mode is exited and RELAX mode is entered when
Current
goes above
(–)Quit Current
threshold
for a period of
Dsg Relax Time
. CHARGE mode is entered when
Current
goes above
Chg Current Threshold
.
Time
Current
0
Chg Current
Threshold
Quit Current
(-)Quit Current
Dsg Current
Threshold
RELAX
Mode
CHARGE
Mode
Chg Relax
Time
RELAX Mode
DISCHARGE
Mode
Dsg Relax
Time
RELAX Mode
Figure 6-2. Gas Gauge Operating Mode Example
6.4 QMax and Ra
The total battery capacity is found by comparing states of charge before and after applying the load with the
amount of charge passed. When an applications load is applied, the impedance of each cell is measured by
comparing the open circuit voltage (OCV) obtained from a predefined function for present state-of-charge with
the measured voltage under load.
Measurements of OCV and charge integration determine chemical state-of-charge (SOC) and Chemical
Capacity (
QMax
).
The BQ28Z610-R2 acquires and updates the battery-impedance profile during normal battery usage. It
uses this profile, along with state-of-charge and the
QMax
values, to determine
FullChargeCapacity
and
RelativeStateOfCharge
specifically for the present load and temperature.
FullChargeCapacity
reports a capacity
or energy available from a fully charged battery reduced by
Reserve Cap-mAh
or
Reserve Cap-cWh
under
the present load and present temperature until
Voltage
reaches the
Term Voltage
for a period of
Term V Hold
Time
.
Gauging
38
BQ28Z610-R2
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