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Comparison between BQ24650 and BQ24072 charging current profile

Akshay Deshpande
Intellectual 310 points
Other Parts Discussed in Thread: BQ24072, BQ24650

Hello,

I have a system that takes the input from solar. BQ24650 is used as charge controller. The output of this controller is fed as input to a system that operates with BQ24072 ,a Lithium ion battery charge management ic. The final output is the load. Please refer to the block diagram below for the reference:

Now, my question is that whether BQ24650 charge controller will consider BQ24072 ic as battery? I mean to say will there be any difference in the charging current profile of the two controllers with respect to Li-ion battery??

The Li-ion battery connected is 4 Cell, 3.7 volt, 8Ah battery.

The load operates at around 5 to 7 volts.

  • 0
    TI__Mastermind 31120 points

    The bq24072 is a single cell charger so I assume the 4 cells are in parallel.

    Why not use just the bq24650 to charge the battery?

  • 0 in reply to Charles Mauney
    Intellectual 310 points

    Yes. The cells are in parallel. 

    I already have a system that uses BQ24072 as battery charger. I have to power this system or say charge the battery using solar power. I am not supposed to modify the system. Hence my question that whether BQ24650 can be used to charge the battery with BQ24072 included in the system?

    Also, I was referring to the datasheet of the BQ24650 which has an application circuitry for charging the battery. The datasheet also tells me about the output to be fed to the battery. So another way of asking my query is that does BQ24650 has system output function? If not, then how can I get it?

    Thanks and Regards

  • 0 in reply to Akshay Deshpande
    TI__Mastermind 31120 points

    The bq24650 as so all of the Li-Ion chargers have a charge profile of CC/CV.

    In CC mode the 650 will put out (for a 1A CC programmed example) 1A maximum and then taper once the output hits regulation.  At regulation the output is 4.2W and 4V the output is 4W at 3V it is 3W.  If the solar panel only can put at 2W then the bq24650 will only put out ~1.7W.

    So as long as the bq24072 does not pull more power than the bq24650 puts out, then it will work.

    I believe the bq24072 has input voltage DPM so I guess that this would reduce the charging output of the bq24072 if its input dropped off.

    It will probably work fine, but if there are any issues it would be during the transients (start-up, load transients etc.).

  • 0 in reply to Charles Mauney
    Intellectual 310 points

    how can these transients (start-up, load , etc..) be reduced?

  • 0 in reply to Akshay Deshpande
    TI__Mastermind 31120 points

    Designing so the '650 is always on when the '072 turns on.

    Since these two IC are typically not put together we do not have any data on how well they work together.  I suggest you get both EVMs and try some tests and see what happens and if you have any issues we can discuss them.