BQ2060SS Datasheet, PDF (43/59 Pages) Texas Instruments – SBS V1.1-COMPLIANT GAS GAUGE IC

bq2060
www.ti.com
SLUS035E – JANUARY 2000 – REVISED OCTOBER 2005
EEPROM PROGRAMMING (continued)
The graphs in Figure 11 and Figure 12 show the calculated EDV0, EDV1, and EDV2 thresholds versus capacity
using the typical compensation values for different temperatures and loads for a Li-ion 3s3p 18650 pack. The
compensation values vary widely for different cell types and manufacturers and must be matched exactly to the
unique characteristics for optimal performance.
Overload Current Threshold
The Overload Current threshold is a 16-bit value stored in EE 0x46-0x47 in mA units.
Battery Low % =7%, Temperature = 35 C
11500
11000
EDV2
10500
EDV1
10000
35C/500 mA
35C/1 A
9500
35C/2 A
9000
8500
8000
7500
EDV0
7000
10 9 8 7 6 5 4 3 2 1 0
% Capacity
Figure 12. EDV Calculations vs. Capacity for Various Loads
Midrange Capacity Corrections
Three voltage-based thresholds, VOC25 EE 0x6c–0x6d, VOC50 EE 0x6e–0x6f, and VOC75 EE 0x70–0x71, are
used to test the accuracy of the RM based on open-circuit pack voltages. These thresholds are stored in the
EEPROM in 2s complement of voltage 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
EE 0x53 by the following relation:
ǒ Ǔ Self * Discharge Rate + 256 *
52.73
%PERDAY
(13)
Light Load Current
The amount of light load current in mA, ILEAK, used for compensation is stored in Light Discharge Current in EE
0x2b as follows:
Light
Discharge
Rate
+
ILEAK
45
1024
(14)
ILEAK is between 0.044 mA and 11.2 mA.
Charge Efficiency
The bq2060 uses four charge-efficiency factors to compensate for charge acceptance. These factors are coded
in Charge Efficiency, Efficiency Reduction Rate, Efficiency Drop Off Percentage, and Efficiency Temperature
Compensation.
The bq2060 applies the efficiency factor, EFF%, when RelativeStateOfCharge() is less than the value coded in
Efficiency Drop Off Percentage EE 0x64. When RelativeStateOfCharge() is greater than or equal to the value
coded in Efficiency Drop Off Percentage, EFF% and ERR% determine the charge efficiency rate. ERR% defines
the percent efficiency reduction per percentage point of RelativeStateOfCharge() over Efficiency Drop Off
Percentage. EFF% is encoded in High Charge Efficiency EE 0x4d according to the following equation:
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