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Original question:

two 18650 litium ion batteries cell

Charger IC for 2x 18650 in parallel

J.Schweiger
Expert 1745 points
Other Parts Discussed in Thread: BQ25616, BQ24040, BQ21040, BQ25611, BQ24295, BQ25606, BQ25611D

Hello, I have a related question in wanting to charge 2x 18650 batteries in parallel (3.7V, 5Ahr combined).  I've looked at the suggested BQ25616 and note in the description it says "for single cell Li-Ion".  Is this part actually designed for charging multiple cells in parallel, or was it selected simply because it has much higher charging capacity?  In my application, charge time is not important and I am wondering if I can use more cost effective BQ21040 or BQ24040.

  • 0
    TI__Intellectual 1640 points

    Hi,

    1S2P is interpreted as "single cell Li-ion" since the battery voltage of 1S2P would be similar to that of 1S1P, 1S2P, 1S3P, and so on, if they're in a pack. 

    You can use either BQ21040 or BQ24040 if charge time is not important. BQ21040 and BQ24040 are linear charger whereas BQ25616 is a Switching charger. 

  • 0 in reply to Upal Patel
    Expert 1745 points

    Thank you Upal. 

    After talking with my client, she wants to move forward with the higher power option.  I realize you have a lot of options here and the comparison tool on TI isn't much help in understanding the difference so I'm hoping you can help clarify.  FYI, my new list of components is now the BQ25616 as mentioned before, but also lower cost BQ24295 and BQ25606.  I also found the new component BQ25611.  Of course if you have alternate suggestions I would appreciate this.  The goal on my end is to get the most cost effective device that meets our requirements and makes design simplest.

    Our system will be charging from a USB C connection. 5V/3A should be plenty sufficient for our 2x18650 battery so I don't see need to consider higher voltage options.

    It seems the lowest cost option BQ24295 has everything we want, including:
    -USB charge current negotiation (getting 5V/3A from compatible chargers, or negotiating lower limits if lower power power source is attached).
    -Power path (ability to pass 5V/3A power when battery is low/disconnected)
    -Charging/Charge complete outputs
    -20uA quiescent current (I assume this is current drawn when charger is disconnected.  Lower is always better, but 20uA is quite reasonable.  I see the 25616 and 25611 have 9.5uA here, but don't think that's worth the extra cost to us)

    I see it also has I2C for more detailed communication, but I don't think we'll even use this.  I do realize that BQ24295 has a limited operating voltage range compared to the other options, but I am okay with this as we only intend to use USB C charging at 5V.

    Do you have any insight on why I might want to consider any of the other options, or would you recommend going with this lowest cost option (given 5V/3A with power path)?

    Thank you,
    -Jon

  • 0 in reply to J.Schweiger
    TI__Intellectual 1640 points

    Hi Jon,

    You can certainly use BQ24295 for your application, as it seems like this would be perfect fit for your system and is cost optimized as well. If you want higher functionality with wider input voltage range, lower Iq, then BQ25616 and BQ25611D would be your options.