• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 64 subscribers
  • Views 240 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ77307: Inverse battery protection for BQ77307

Eli Hait54
Prodigy 240 points
Part Number: BQ77307

Tool/software:

Hello, all.

In my case the battery consists of 4 removable cells. The user may insert one or more of the cells in reverse polarity.
In such a situation, the Q77307 must be protected from damage.

The question is, is it possible to simply connect a diode in parallel to each input of a cell after the resistor between GND-VC0, VC0-VC1, VC1-VC2, VC2-VC3?

Or it better to connect serial diodes to VC0, VC1, VC2, VC3?

Thanx,
Eli.

  • 0
    TI__Mastermind 41720 points

    Hello Eli,

    I am not sure if that's a great solution.

     The cell would be discharged when it is connected backwards. Some of the cells could also potentially be pushed below ground with this configuration. VC0 should not be going much lower below ground.

    Having removable cells like this is not a typical setup for this device, and may not work too well.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 240 points

    Hi, Luis,

    There are several limitations for this battery pack functionality so maybe after all this component can only be used with protection of the inputs against reverse voltage?

    1. The batteries are charged separately outside the module. No need to charge them when they located in the batteries holder.

    2. The batteries protection circuitry will be part of the batteries holder. When all batteries are pushed into the holder, initially they are disconnected from the load so no current is drawn except few milliamps required for this protection circuit to operate and it will not connect the batteries to the load it detect that one or more of the cells is inverse direction, defected or discharged.

    Best Regards,

    Eli Hait.

  • +1 in reply to Eli Hait54
    TI__Mastermind 41720 points

    Hello Eli,

    I understand. Now, if you do follow with this, you have to be careful to ensure that the diodes you choose have a low forward bias voltage. 

    If the diode you choose is too high, current could flow through the die itself and damage it. So these would all have to be Schottky diodes.

    Now, I would advice you test this type of configuration with a protoype board or maybe with an EVM if you can solder them in. You would also have to consider what is the supply voltage, if the supply voltage were to somehow be below 6-V during this process, it could simply SHUTDOWN the BMS.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 240 points

    Thanx, Luis :)