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BQ24014: Low V battery charging

Randy Chen
Intellectual 2200 points
Part Number: BQ24014

Hi,

Customer used 250mAh battery. Test with below 3 conditions.

1. Set R_ISET=3.9K ohm and got the Iout=214mA. Charger BQ24014 failed to charge when the connected battery voltage is 0V. Then disconnected the system load, the charger was able to charge the 0V battery with charge current 213mA.

2. Tested with R_ISET change to 1K ohm and got the Iout=837mA. The system load connected, the charger was able to charge the 0V battery with charge current 400+mA. But this charge current has over battery spec.

3. Tested with R_ISET=1.8K ohm which is the max value can charge to the 0V battery with the system load connected. But the charge current has over 1C.

Please advise how to optimize the R_ISET to get the charge current to 0V battery with the system load connected.

Best regards,

Randy Chen

  • 0
    TI__Guru 74746 points
    Hi Randy
    The problem could be a short circuit current or pre-charge current limit. Below 1.4V battery voltage unit is in short circuit mode and current out is limited to 1mA. But this will not change with R-ISET. Above 1.4V unit is in pre-charge and current is 10% of fast charge current set by R-ISET. Increase in R-ISET may be making a difference in starting.

    If the battery has a protection circuit it may be opening when voltage is low and you see 0V on battery. To reset the battery will need voltage to rise beyond some point. Load from the system may prevent voltage rising enough to reset the protector.

    Some customers have used a load switch to disconnect the system load until battery voltage has increase we can look at this.
    I will email you.