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BQ25171EVM: About the charging circuit of BQ25171EVM 7-cell NiMH rechargeable battery

Part Number: BQ25171EVM

The first thing I need to confirm is that I'm considering a charging circuit for a 7-cell NiMH rechargeable battery with BQ25171EVM.
If I don't use TS, can I pull down TS with 10kΩ?
(Currently, when I pull down the TS with 10kΩ, the charging circuit doesn't work properly.
(Currently, when TS is pulled down at 10kΩ, the charging circuit does not work properly and both STAT1 and STAT2 are not lit.

Secondly, I'm considering a charging circuit for a 7-cell NiMH rechargeable battery with BQ25171EVM.
The TS is not used, but I am trying to keep the TS within the hot and cold thresholds described in the datasheet.
Please tell me the possible reasons.
If the voltage is below 1.05V, it will drop to LOW after startup.
When the voltage is above 1.06V, the voltage stays HIGH but the LED of STAT1 lights up.
The voltage is above 1.06V and stays HIGH, but the LED on STAT1 lights up and the charging does not start.

  • Hello,

    Yes, if TS function is not needed you should pull down TS to GND with 10k res. Can you give more details on what is not working? With 10k res the TS voltage should be around 380 mV. 

    As I have stated in the last post, charging only occurs between the hot and cold thresholds: 188mV to 1.04V

    thanks,

    Nick

  • Hello,

    Thank you for your answer.
    I understand the specs you mentioned, but I'm not sure if it's a good idea to use
    I've checked with a lithium battery, and it seems that even when the TS is 10KΩ pull-down
    It works fine even when the thermistor is connected and set to the recommended constant (RS,RP).

    However, it works only when a NiMH 7-cell battery (Toshiba 6TNH-22A) is connected.

    Even when TS is set to 10KΩ pull-down
    However, when a thermistor is connected and set to the recommended constant (RS,RP), it does not work properly.

    Thanks,

  • Hello,

    Let me be more specific.
    A 3.7V Li-polymer battery has a VSET of 2.4KΩ and a TS voltage of about 380mV.
    In a similar environment
    A 8.4V 7-cell Ni-MH battery has a VSET of 3.6kΩ and a TS voltage of about 0V.
    (There is a rectangular waveform for a moment, but it drops to 0V immediately.
    In short, the behavior of TS is changing depending on the battery connected.
    I would like to know if there is a configuration suitable for NiMH rechargeable batteries.

    Thanks,

  • Hello,

    There was an error in the resistance value of the 3.7V Li-polymer battery above.
    The correct value is 24KΩ. I will correct it.

    Thanks,