DS2435 Datasheet, PDF (3/24 Pages) Dallas Semiconductor – Battery Identification Chip with Time/Temperature Histogram

DS2435
OVERVIEW - TIME/TEMPERATURE HISTOGRAM
Periods of storage are normal for most battery-powered applications. During this storage time, little or no
current is actually drawn from the battery; batteries will, however, lose capacity during this storage time
due to parasitic side reactions in the cell and other electrochemical mechanisms. This loss of capacity is
termed self-discharge.
Since self-discharge is the result of electrochemical reactions, its rate is dependent upon the cell
temperature. Knowing the time spent in certain temperature ranges during the storage time of the battery,
these temperature effects may be factored into a calculation of self-discharge for the battery. This will
allow a more accurate determination of retained battery capacity.
The DS2435 measures, tabulates, and stores this information in the battery pack. It periodically measures
the battery temperature, and updates the appropriate temperature “bin” of the time/temperature histogram
with the time spent in that temperature range. The resulting histogram data could appear graphically as
shown in Figure 2.
The DS2435 allows for eight temperature ranges, or bins, to be specified by fixing the values of the bin
limits, TA through TG. Once specified, the time spent in each of the bins (bin 1 being anything less than
TA, bin 2 being temperature greater than or equal to TA but less than TB, etc., and bin 8 being anything
greater than or equal to TG) is recorded (t₁ being the time spent in bin 1, t₂ the time spent in bin 2, etc.).
Using this information and data from the battery manufacturer regarding retained capacity, the actual
battery capacity remaining may be closely approximated by the user.
TIME/TEMPERATURE HISTOGRAM Figure 2
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