
DS2782: Stand-Alone Fuel Gauge IC 
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Minimum Charge Current (IMIN):
IMIN
 stores the charge current threshold used to detect a fully charged state. 
The value is stored as a 1-byte value with units of 50 V and can range from 0 to 12.75mV. Assuming RSNS = 
20m , IMIN can be programmed from 0mA to 637.5mA in 2.5mA steps. IMIN should be set marginally greater than 
the charge current at the end of the charge cycle to ensure reliable charge termination detection. IMIN is located in 
the Parameter EEPROM block. 
Active Empty Voltage (VAE):
 VAE stores the voltage threshold used to detect the Active Empty point. The value 
is stored in 1-byte with units of 19.52mV and can range from 0V to 4.978V. VAE is located in the Parameter 
EEPROM block. See the 
Cell Characteristics
 section for more information.  
Active Empty Current (IAE):
IAE
 stores the discharge current threshold used to detect the Active Empty point. 
The unsigned value represents the magnitude of the discharge current and is stored in 1-byte with units of 200 V 
and can range from 0 to 51.2mV. Assuming RSNS = 20m , IAE can be programmed from 0mA to 2550mA in 
10mA steps. IAE is located in the Parameter EEPROM block. See the 
Cell Characteristics
 section for more 
information. 
Aging Capacity (AC):
 AC stores the rated battery capacity used in estimating the decrease in battery capacity that 
occurs in normal use. The value is stored in 2-bytes in the same units as the ACR (6.25 Vh). Setting AC to the 
manufacturer’s rated capacity sets the aging rate to approximately 2.4% per 100 cycles of equivalent full capacity 
discharges. Partial discharge cycles are added to form equivalent full capacity discharges. The default estimation 
results in 88% capacity after 500 equivalent cycles. The estimated aging rate can be adjusted by setting AC to a 
different value than the cell manufacturer’s rating. Setting AC to a lower value, accelerates the estimated aging. 
Setting AC to a higher value, retards the estimated aging. AC is located in the Parameter EEPROM block. 
Age Scalar (AS):
 AS adjusts the capacity estimation results downward to compensate for cell aging. AS is a 1-byte 
value that represents values between 49.2% and 100%. The lsb is weighted at 0.78% (precisely 2
). A value of 
100% (128 decimal or 80h) represents an un-aged battery. A value of 95% is recommended as the starting AS 
value at the time of pack manufacture to allow learning a larger capacity on batteries that have an initial capacity 
greater than the nominal capacity programmed in the cell characteristic table. AS is modified by the cycle count 
based age estimation introduced above and by the capacity Learn function. The host system has read and write 
access to AS, however caution should exercised when writing AS to ensure that the cumulative aging estimate is 
not over written with an incorrect value. Usually, writing AS by the host is not necessary because AS is 
automatically saved to EEPROM on a periodic basis by the DS2782. (See the 
Memory
 section for details.) The 
EEPROM stored value of AS is recalled on power-up. 
CAPACITY ESTIMATION UTILITY FUNCTIONS 
Aging Estimation 
As discussed above, the AS register value is adjusted occasionally based on cumulative discharge. As the ACR 
register decrements during each discharge cycle, an internal counter is incremented until equal to 32 times AC. AS 
is then decremented by one, resulting in a decrease in the scaled full battery capacity of 0.78%. Refer to the AC 
register description above for recommendations on customizing the age estimation rate.  
Learn Function 
Since Li+ cells exhibit charge efficiencies near unity, the charge delivered to a Li+ cell from a known empty point to 
a known full point is a dependable measure of the cell capacity. A continuous charge from empty to full results in a 
“l(fā)earn cycle”. First, the Active Empty point must be detected. The Learn Flag (
LEARNF
) is set at this point. Then, 
once charging starts, the charge must continue uninterrupted until the battery is charged to full. Upon detecting full, 
LEARNF
 is cleared, the Charge to Full (
CHGTF
) flag is set and the Age Scalar (AS) is adjusted according to the 
learned capacity of the cell. 
ACR Housekeeping  
The ACR register value is adjusted occasionally to maintain the coulomb count within the model curve boundaries. 
When the battery is charged to full (
CHGTF
 set), the ACR is set equal to the age scaled full lookup value at the 
present temperature. If a learn cycle is in progress, correction of the ACR value occurs after the age scalar (AS) is 
updated.