Texas Instruments bq76930, User Manual, Page: 24 / 61

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Figure 13. Chemistry View
5.8 Calibration
The EVM and all new boards should be calibrated before operation. The calibration view is shown in
Figure 14 . Temperature is typically calibrated first. Current Offset should be calibrated with no current flow
and should be calibrated before Current Gain. The EVM uses a 1-m
Ω
sense resistor and calibration at low
current will result in some granularity from the current resolution. This may result in an apparent error at
higher currents. Calibration at higher currents will reduce this effect and should be done where it is
important.
By default, the bq78350 uses the average cell voltage for gauging. This voltage must be calibrated.
Measure the battery voltage, calculate the average cell value and enter the value in the box. Clicking the
Calibrate Voltage button runs the calibration. Values left blank or entered as '0' are not calibrated. When
successful, a green check appears next to the button as shown in
Figure 15 . If there is an error, a red X
appears instead with a message. The bq769x0 contains factory voltage calibration data for cell voltage
values. The bq78350 uses this data to determine the individual cell voltage. When it is desired to calibrate
each cell's offset rather than relying on the average stored in the bq769x0, individual cell voltages can be
measured and calibrated. Cells can be calibrated in groups or individually by entering or clearing the
desired values.
Basic steps for calibration of the EVM is described in the quick start section. Since the EVM uses 1%
values for the cell simulator resistors, measuring each cell voltage value is recommended rather than
using a common value if individual cell voltage calibration is desired.
24 bq76930 and bq76940 Evaluation Module User's Guide SLVU925B – April 2014 – Revised July 2014
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