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bq20z95 odd cell voltage readings

Andrew Newton
Prodigy 120 points

Hello all,

I'd welcome some input please if you'd be so kind. I have a system running the above part and the system works operationally however the individual cell voltage readings are really quite strange. 

I have a two cell system and am reading an overall voltage of (say) 7700 mV although the cell voltages read as 3331 mV and 4433 mV (cell 1 and cell 2 respectively). This is simulating a battery with two 1% precision resistors.

If you need any further information, I'll happily provide it but I think it may be a calibration setting which I have overlooked or something that others may have seen in their own development. But any ideas would be most appreciated. 

Kindest thanks.  

  • 0
    TI__Genius 10235 points

    Measure the voltage at the point the resistors connect to the board and then measure the voltages at the VC1 and VC2. If the voltage is good at the resistors but bad at the pins, there is likely a component damaged on the board. Check the 100Ohm resistor and 0.1u cap on each line to make sure they are still good. Also check the values to make sure they are correct. If that doesn't check out, the IC may be damaged. Try it on another board as well to see if the problem goes away

  • 0 in reply to Chase7071949597
    Prodigy 120 points

    Many thanks for your comments. Very much appreciated.

    By way of some initial feedback I can tell you that I see this on all the boards but the device is so highly configurable that I really have taken a long time to get upto speed with the setting up of all of the parameters. The rather consistent 1000 mV difference does tend to suggest I have an inadvertent potential divider hidden somewhere in here however, although I have been unable to get near the equipment to check that out at this stage. I can do that today. I can't spot it on the schematic!

    Again, thanks for your comments.