The bq2011 determines battery capacity by monitoring
the amount of charge input to or removed from a re-
chargeable battery. The bq2011 measures discharge and
charge currents, estimates self-discharge, monitors the
battery for low-battery voltage thresholds, and compen-
sates for temperature and charge/discharge rates. The
charge measurement is made by monitoring the voltage
across a small-value series sense resistor between the
negative battery terminal and ground. The available
battery charge is determined by monitoring this voltage
over time and correcting the measurement for the envi-
ronmental and operating conditions.
Figure 1 shows a typical battery pack application of the
bq2011 using the LED display with absolute mode as a
charge-state indicator. The bq2011 can be configured to
display capacity in either a relative or an absolute dis-
play mode. The relative display mode uses the last
measured discharge capacity of the battery as the bat-
tery “full” reference. The absolute display mode uses the
programmed full count (PFC) as the full reference, forc-
ing each segment of the display to represent a fixed
amount of charge. A push-button display feature is
available for momentarily enabling the LED display.
The bq2011 monitors the charge and discharge currents
as a voltage across a sense resistor (see R
in Figure 1).
A filter between the negative battery terminal and the
SR pin may be required if the rate of change of the bat-
tery current is too great.
Gas Gauge IC
Directly connect to VCC across 4 cells (4.8V nominal and should not
exceed 6.5V) with a resistor and a Zener diode to limit voltage during charge.
Otherwise, R1, C1, and Q1 are needed for regulation of >4 cells.
Programming resistors and ESD-protection diodes are not shown.
R-C on SR may be required, (application-specific), where the maximum
R should not exceed 20K.
Figure 1. Battery Pack Application Diagram—LED Display,
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