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Introduction
67
SLUUBD3D–September 2015–Revised September 2018
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Copyright © 2015–2018, Texas Instruments Incorporated
CEDV Gas Gauging
9.1.11 Self Discharge
The bq78350-R1 estimates the self-discharge of the battery to maintain an accurate measurement of the
battery capacity during periods of inactivity. The bq78350-R1 makes self-discharge adjustments to RC
every ¼ second when awake and periodically when in SLEEP mode. The period is determined by Sleep
Current Time.
The self-discharge estimation rate for 25°C is doubled for each 10 degrees above 25°C or halved for each
10 degrees below 25°C. The table below shows the relation of the self-discharge estimation at a given
temperature to the rate programmed for 25°C.
Temperature (°C) Self-Discharge Rate (Average)
Temp < 10 ¼ Y% per day
10 ≤ Temp < 20 ½ Y% per day
20 ≤ Temp < 30 1 Y% per day
30 ≤ Temp < 40 2 Y% per day
40 ≤ Temp < 50 4 Y% per day
50 ≤ Temp < 60 8 Y% per day
60 ≤ Temp < 70 16 Y% per day
70 ≤ Temp 32 Y% per day
The nominal self-discharge rate, %PERDAY (% per day), is programmed in an 8-bit value Self-Discharge
Rate by the following relation:
Self-Discharge Rate = %PERDAY/ 0.01
Class Subclass Name Format
Size in
Bytes
Min Max Default Unit
Fuel
Gauging
CEDV Cfg
Self
Discharge
Rate
Unsigned
Integer
1 0% 255% 20% 0.01/day
9.1.12 Battery Electronic Load Compensation
The bq78350-R1 can be configured to compensate for a constant load (as from battery electronics)
present in the battery pack at all times. The bq78350-R1 applies the compensation continuously when the
charge or discharge is below the digital filter. The bq78350-R1 applies the compensation in addition to
self-discharge.
The compensation occurs at a rate determined by the value stored in Electronics Load. The
compensation range is 0 µA – 765 µA in steps of approximately 3 µA.
The amount of internal battery electronics load estimate in µA, BEL, is stored as follows: Electronics
Load = BEL/3.
Class Subclass Name Format
Size in
Bytes
Min Max Default Unit
Fuel
Gauging
CEDV Cfg
Electronics
Load
Integer 2 0 255 0 3 µA
9.2 Gauging Configuration Options
The bq78350-R1 has a variety of configurable options that can be configured, enabled, or disabled
through the following data flash options.
Class Subclass Name Type Min Max Default Unit
Gas Gauging Design Design Capacity mAh I2 0 32767 4400 mAh
Gas Gauging Design Design Capacity cWh I2 0 32767 6336 cWh
Gas Gauging Design Design Voltage I2 0 5000 3600 mV
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