BQ2060 Datasheet, PDF (33/51 Pages) Texas Instruments – SBS v1.1-Compliant Gas Gauge IC

bq2060
n C (0%, 3%, or Battery Low % for EDV0, EDV1, and
EDV2, respectively) and C0 are the capacity related
EDV adjustment factors. C0 is programmed in the
lower 11 bits of EDV C0 Factor/EDV2 EE 0x78–79.
The Residual Capacity Factor is stored in the upper 5
bits of EE 0x78–0x79.
Residual Capacity Factor C1 =RESIDUAL% * 2.56
RESIDUAL % is the desired battery capacity remaining
at EDV0 (RM = 0).
n T is the current temperature in °K
R0 ∗ FTZ represents the resistance of the battery as a
function of temperature and capacity.
FTZ = f ( R1 , T0, T, C + C1)
(11)
n R0 is the first order rate dependency factor stored in
EDV R0 Factor EE 0x7a–0x7b.
n T is the current temperature; C is the battery
capacity relating to EDV0, EDV1, and EDV2; and C1
is the desired residual battery capacity remaining at
EDV0 (RM = 0).
n R1 adjusts the variation of impedance with battery
capacity. R1 is programmed in EDV R1 Rate Factor
EE 0x7c–0x7d.
n T0 adjusts the variation of impedance with battery
temperature. T0 is programmed in EDV T0 Rate
Factor EE 0x76–0x77.
FCY is the factor that adjusts for changing cell imped-
ance as the battery pack is cycled.
where
FCY = f(A0, CycleCount())
(12)
n A0 is the EDV aging factor that is stored in EDV A0
Factor EE 0x06. It should be set to 0 for most
applications.
Typical values for the EDV compensation factors for a
Li-Ion 3s3p 18650 pack are
EMF = 11550
T0 = 4475
C0 = 235
C1 = 0
R0 = 5350
R1 = 250
A0 = 0
The graphs in Figures 7 and 8 show the calculated
EDV0, EDV1, and EDV2 thresholds versus capacity us-
ing 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.
11500
Battery Low %= 7%, Load = 500mA
11000
EDV2
10500
EDV1
10000
9500
9000
8500
8000
45C/500mA
20C/500mA
7500
10 9 8 7 6 5 4 3 2 1 0
% Capacity
Battery Low % =7%, Temperature = 35 C
11500
11000
EDV2
10500
EDV1
10000
9500
9000
8500
8000
35C/500mA
35C/1A
35C/2A
7500
EDV0
7000
10 9 8 7 6 5 4 3 2 1 0
% Capacity
Figure 7. EDV Calculations vs. Capacity
for Various Temperatures
Figure 8. EDV Calculations vs. Capacity
for Various Loads
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