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BQ27220: BQ27220 design issue

Sherman Xin
Prodigy 350 points
Part Number: BQ27220
Other Parts Discussed in Thread: BQ25155

My customer meets some design issues about BQ27220. Pls help review below description:

There are 4 independent batteries, the analog switch is used to switch different batteries as supply power of the system, BQ25155 and BQ27220 are used here. The connection method is as shown below, Please help answer the following 3 questions:

1. Can one BQ27220 monitors 4 batteries by time-sharing? 
2. Do you have any suggestions to monitor the power of each battery? Do we need 4 pcs BQ27220?
3. Assuming that 4 batteries are connected in parallel, will it affects the charging/discharging and capacity monitor of the BQ27220? 

Best regards,

Sherman

  • 0
    TI__Guru** 102375 points

    Hello Sharman,

    Each battery should have a separate gauge if they are not in parallel. If they are in parallel and all being charged/discharged together, then you can use one gauge.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Prodigy 350 points

    Hi Wyatt,

    Thanks for your reply! The battery are in parallel, and they use analog switch to switch 4 battery, they want to know if one BQ27220 can monitor the 4 battery in different time periods. For example, first ten minutes we monitor 1st battery, second 10 minutes we monitor 2st battery...Does this circuit make sense here?

    Best regards,

    Sherman

  • 0 in reply to Sherman Xin
    TI__Guru** 102375 points

    Hello Sherman,

    You cannot use one gauge with a power mux to switch to gauging multiple separate packs. The gauge relies on coulomb counting and learning the FCC for the pack it is attached to. Gauging would not work properly using this method of switching between batteries often. They should use a gauge for each battery if the batteries are not always in parallel with each other.

    Sincerely,

    Wyatt Keller