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BQ21040: Add NTC resistor to battery pack

Michele Bertoni1
Intellectual 340 points
Part Number: BQ21040

Hi to all, I would like to use BQ21040 to charge LiPo battery.
Previous battery I used had internal NTC resistor (so 3 wires), then batteries are not available, then I had to use simple (2 wires) battery pack.
It's reported BQ21040 uses 10 kOhm NTC: is it safe mount 0805 case NTC resistor on PCB, on direct contact to 18650 battery case?
Also talking about temperature: is it safe keep maximum charge current to 500mA in a sealed enclosure for outdoor portable device or should I go down to 250mA?
Thanks.

  • 0
    TI__Guru* 75656 points

    Hello

    The best solution will depend on your system requirements and specifications regarding battery safety vs charging temp. 

    Your proposal to use an 0805 NTC resistor on the PCB located near the battery is reasonable.  Also reducing the charge current in an outdoor (possibly hot) environment is also good approach.