BQ2085 Datasheet, PDF (45/56 Pages) Texas Instruments – SBS-COMPLIANT GAS GAUGE IC FOR USE WITH THE bq29311

bq2085
SLUS541 – OCTOBER 2002
11.5
11.0
EDV2
10.5
EDV1
10.0
VOLTAGE
vs
CAPACITY
Battery Low % = 7%
Load = 500 mA
20°C
45°C
9.5
9.0
8.5
11.5
11.0
EDV2
10.5
EDV1
10.0
9.5
VOLTAGE
vs
CAPACITY
Battery Low % = 7%
TA = 35°C
500 mA
1A
2A
9.0
8.5
8.0
8.0
7.5
0 1 2 3 4 5 6 7 8 9 10
Capacity – %
7.5
EDV0
7.0
0 1 2 3 4 5 6 7 8 9 10
Capacity – %
Figure 8. EDV Calculations vs Capacity for
Various Temperatures
Figure 9. EDV Calculations vs Capacity for
Various Loads
Overload Current Threshold
The overload protection disables discharge when the 16-bit limit programmed in DF 0x58–0x59 is breached.
The threshold is stored in mA.
Midrange Capacity Corrections
Three voltage-based thresholds, VOC25 DF 0x78–0x79, VOC50 DF 0x73–0x74, and VOC75 DF 0x6e–0x6f,
are used to test the accuracy of the RM based on open-circuit pack voltages. These thresholds are stored in
the data flash in mV. The values represent the open-circuit battery voltage at which the battery capacity should
correspond to the associated state of charge for each threshold.
Self-Discharge Rate
The nominal self-discharge rate, %PERDAY (% per day), is programmed in an 8-bit value Self-Discharge Rate
DF 0x2c by the following relation:
Self-Discharge
Rate
+
%PERDAY
0.01
(8)
Charge Efficiency
The bq2085 applies the efficiency factor, EFF%, to all charge added to the battery. EFF% is encoded in Charge
Efficiency DF 0x51 according to equation 16:
Charge Efficiency + (EFF% • 2.56–1)
(9)
Other Compensation
Battery Electronics Load
The amount of internal battery electronics load estimate in µA, BEL, is stored in Electronics Load DF 0x2d as
follows:
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