Texas Instruments SLUU083A - Manual (Page 11)

Test Procedures
2-4
The bq2400x enters preconditioning mode if the battery is below the LowV
threshold. In this mode, the bq2400x trickle-charges with approximately
65 mA for approximately 23 minutes. If the battery does not reach the LowV
threshold after this period, then the charge current is terminated and the
bq2400x enters fault mode. The red LED flashes in fault mode. This feature
is tested in the 0.5-A charge mode by using a 10-
Ω
, 5-W resistor in place of
the battery. Fault mode is reset by toggling input power or enable pin.
Once the battery charges to the LowV-stop threshold, the battery enters fast
charge mode and charges at the selected Ichg level (0.5 A/1 A).
The battery remains at the fast charge mode until either the selected time
expires or the battery charges to the selected regulation voltage.
The timeout feature is tested in the 0.5-A charge mode by using a 14-
Ω
, 5-W
resistor in place of the battery. Apply the resistor after the unit is powered up.
Once the battery voltage reaches voltage regulation (8.2 or 8.4 VDC), the
charge current tapers off as the battery charges.
If the battery discharges down to the HighV threshold, the charger starts fast
charging. The refresh feature is tested, in the 0.5-A charge mode, by using a
14-
Ω
5-W resistor in parallel with a fully charged battery.
The circuit has an overvoltage comparator for added protection. If the battery
voltage exceeds this threshold for 330 ms, then the charger goes into fault
mode. This process may be tested by connecting an external power supply in
place of the battery and adjusting the voltage above the threshold.