BQ2085-V1P2 Datasheet, PDF (13/56 Pages) Texas Instruments – SBS-COMPLIANT GAS GAUGE IC FOR USE WITH THE bq29311

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1200
CAPACITY
vs
TIME
bq2085−V1P2
SLUS590 − DECEMBER 2003
1000
800
T_A = 15°C
600
T_A = 25°C
400
200
0
0
T_A = 35°C
T_A = 45°C
10
20
30
40
50
60
70
Time − Days
Figure 4. Self-Discharge at 2.5%/Day at 25°C
Figure 4 illustrates how the self-discharge estimate algorithm adjusts RemainingCapacity( ) versus
temperature.
Battery Electronic Load Compensation
The bq2085−V1P2 can be configured to compensate for a constant load (as from battery electronics) present
in the battery pack at all times. The bq2085−V1P2 applies the compensation continuously when the charge or
discharge is below the digital filter. The bq2085−V1P2 applies the compensation in addition to self-discharge.
The compensation occurs at a rate determined by the value stored in Electronics Load DF 0x2d. The
compensation range is 0 µA–765 µA in steps of approximately 3 µA.
Midrange Capacity Corrections
The bq2085−V1P2 applies midrange capacity corrections when the VCOR bit is set in Gauge Configuration DF
0x29. The bq2085−V1P2 adjusts RM to the associated percentage at three different voltage levels: VOC25,
VOC50, and VOC75. The VOC values represent the open circuit battery voltage at which RM corresponds to
the associated for each threshold.
For the midrange corrections to occur, the temperature must be in the range of 19°C to 31°C inclusive and the
Current( ) and AverageCurrent( ) must both be between −64 mA and 0. The bq2085−V1P2 makes midrange
corrections as shown in Table 5. For a correction to occur, the bq2085−V1P2 must detect the need for correction
twice during subsequent 20-s intervals. With the VCOR bit set, the bq2085−V1P2 makes midrange corrections
whenever conditions permit. If the OTVC bit in Gauge Configuration DF 0x29 is set and VCOR = 0, the
bq2085−V1P2 makes a single attempt of mid-range correction immediately after device reset and does not
require a second validation.
Table 5. Midrange Corrections
Voltage( )
CONDITION
≥ VOC75 and RelativeStateOfCharge( ) ≤ 63%
< VOC75 and RelativeStateOfCharge( ) ≥ 87%
≥VOC50 and RelativeStateOfCharge( ) ≤ 38%
<VOC50 and RelativeStateOfCharge( ) ≥ 62%
≥ VOC25 and RelativeStateOfCharge( ) ≤ 13%
< VOC25 and RelativeStateOfCharge( ) ≥ 37%
RESULT
RelativeStateOfCharge()→75%
RelativeStateOfCharge()→75%
RelativeStateOfCharge()→50%
RelativeStateOfCharge()→50%
RelativeStateOfCharge()→25%
RelativeStateOfCharge()→25%
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