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Original question:

BQ24010: Suitable for sub 0C charging?

BQ24010: Alternative that supports charging at -30C with a solar panel

Ruimtepuin
Prodigy 80 points
Part Number: BQ24010
Other Parts Discussed in Thread: BQ25171-Q1, BQ25176M, BQ24210, BQ24040

Hello,

I've been suggested an alternative to the BQ24010, the BQ25171-Q1, because the operating temperature is 0C instead of the required -30C. However, I found out while testing that it wasn't working well for the application.

The input of the charger is connected to a 2W solar panel and when there's not much light the BQ25171-Q1 constantly switches itself off because it loads the solar panel too much causing it to go into the UVLO state. You can see the input voltage of the charger here with its pulsing behavior here:

Do you have any suggestions on chargers that will limit the current for high impedance sources and adhere to the following specifications:

  1. Max input voltage: >7.5V
  2. Max charge current: >350mA
  3. Charge voltage: 4.0-4.2V
  4. Operating temperature: -30C - +80C
  5. Adjustable temperature protection

Thanks in advance!

Martin

  • 0
    TI__Guru* 75856 points

    Hi Martin

    Take a look at the BQ25176M (new device) it has Vin DPM that will reduce output current to prevent overload on input.

  • 0 in reply to Bill Johns
    Prodigy 80 points

    Hi Bill,

    Thanks for the recommendation. It seems to be a good option, but I'm missing an NTC input to only allow charging in a specific temperature range.

    If there's no other alternative I'll maybe look into implementing this in a separate solution.

  • 0 in reply to Ruimtepuin
    TI__Guru* 75856 points

    Hi Martin

    The temp (-30C) is typically determined by an NTC in the battery pack, is this the configuration?  What is the NTC value? Can it be changed?

  • 0 in reply to Bill Johns
    Prodigy 80 points

    Hi Bill,

    In this case the NTC is not inside the battery pack, but on the outside. I can change the configuration and value of it to match the chargers' thresholds.

  • 0 in reply to Ruimtepuin
    TI__Mastermind 23410 points

    Hi Martin,

    Are you able to provide the NTC value? We'll see if there's a solution we can come up with using your existing NTC with the BQ25176M but it'd be good to have the NTC's Beta value.

    Best Regards,

    Anthony Pham

  • 0 in reply to Anthony P Pham
    Prodigy 80 points

    Hi Anthony,

    It's a 10kR NTC with a beta of 3380K. Here's the MPN: ERT-J0EG103FA.

    Regards,

    Martin

  • 0 in reply to Ruimtepuin
    TI__Guru* 75856 points

    Hi Martin

    The BQ25176M has the Input-DPM we want but does not support TS pin, this would need to manage externally, separate circuit.

    Another device to look at is the BQ24210 it is designed to operate from a solar cell.  Has a TS input and adjusted the high / low temp with external resistors.

    BQ24040 has input DPM also. 

  • 0 in reply to Bill Johns
    Prodigy 80 points

    Hi Bill,

    I have already implemented the BQ24210 in the design and it is working great. The issue though is that the absolute maximum rating is in spec, but the recommended not, in terms of operating temperature. Most chargers only seem to be testes down to 0C, which is not enough for the application. I have done quite some testing already at -30C and the BQ24210 is working great, but if I can't get a guarantee that it will always be working well then it's not worth the risk.

    If I would operate the BQ24210 outside of the recommended operating temperature, is there a possibility it will fail? My assumption would be that it doesn't really matter if it was exposed to cold temperature as ICs generally work much better when it gets colder. Or is this a false assumption?

    The BQ24040 unfortunately has the same issue. I could consider the BQ25176M, but if I need to implement a separate temperature switch it does add some risk.

    Regards,
    Martin

  • 0 in reply to Ruimtepuin
    TI__Guru* 75856 points

    Hi Martin

    I am checking on the temp range of BQ24210.  It is spec at 0C to 125C, Electrical Characteristics Table Specficaiion. Device will operate down to -40C.

    Calculations on TS pin with Rs and Rp, resistors to adjust hot and cold show that it may be possible with the above NTC.  

    Would the BQ24210 be your first choice if temp range and TS / NTC can be resolved?

  • 0 in reply to Bill Johns
    Prodigy 80 points

    Hey Bill,

    If the temperature range is okay (i.e. I can use it below 0C for charging) then it would really like to use it. I've already done a lot of tests on this charger and it works really well for the application, it's just that I don't want to get broken devices in the field because of out-of-spec use.

    Regards,
    Martin

  • 0 in reply to Ruimtepuin
    TI__Guru* 75856 points

    Hi Martin

    I have a possible option but need to discuss with you off-line, we can set up private conversation using PM feature of forum. Watch for message from me.