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Original question:

CCS/BQ76920: Code debugging

CCS/BQ76920: Battery balancing problem

user4413695
Prodigy 230 points
Part Number: BQ76920

Tool/software: Code Composer Studio

Hello，I have two problems. Please help me out：

Question 1：I have four batteries, so the actual 4 and 5 legs of the con6 are short.Is the equalization that the chip will automatically detect the pressure difference between the battery pack to make the action?Or do I need my software to detect the voltage of 4 sets of batteries, and then write the corresponding value to register CELLBAL1 in real time to control the battery discharge according to the battery pressure difference?

Question 2：Data sheet indicate that adjacent batteries cannot be balanced at the same time, but CB0:VC0~VC1, CB1:VC1~VC2, CB2:VC2~VC3, CB3:VC3~VC4, CB4:VC4~VC5(short connection), CB5:VC5~VC6,

So if I set CB4 to 0 all the time, then things like CB0 and CB1 can't be balanced at the same time, what about CB3 and CB5?Is it adjacent?

Attached schematic

  • 0
    TI__Guru 54715 points
    Hi User,
    1. The bq76920 will auto-detect that the cell 4 (VC4-VC3) voltage is approximately 0 and not include that cell in the UV comparison. But your software must determine which cells to balance and when. For 4 cells we would recommend you short CON6 pins 4-5, short C3, and remove R8 and R13 to remove the parallel path. R2, Q2 and Dz2 would not be used and could also be removed.

    2. Yes, when configured for 4 cells VC3 and VC4 are connected together or to the same voltage and are now physically adjacent. CB3 and CB5 should be considered adjacent and not balanced at the same time. You might do an analysis and check to see if voltages are in safe levels at all conditions in your implementation, but our recommendation is to consider them adjacent and not balance at the same time.