Test Procedures

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.

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