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Prevent/detect wrong polarity of charger on BMS

Savvas Kokkinidis
Prodigy 70 points
Other Parts Discussed in Thread: BQ76200

Hello, is there any recommended circuit or IC that will prevent (and detect) damage from wrong polarity of charger on BMS? 

I have already read the below applcation report but we need something more reliable:

bq76200 Reverse Voltage Considerations

  • 0
    TI__Expert 3425 points

    Hi Savvas, 

    This is a common circuit we use for protecting against reverse charger connection with the diode preventing reverse currents from flowing.  In some cases, depending on the application, we have seen the customer include redundant circuits as well. 

    Can we know why this flyback diode would not be sufficient for your application? 

    What are you meaning by 'more reliable'?  

    Would you mind sharing more details on the type of application you will be using and requirements that you are looking for?  

    Best, 

    -Luis Torres

  • 0 in reply to Luis Torres
    Prodigy 70 points

    We are working on a 48V BMS. 

    For the flyback, are you referring to the first case of the application report? In this case, there will be short circuit on the charger's side. I am not sure if this is accepted from charger's side since we are still in development and have minimum information about the charger.

    We could use an XT connector which will prevent from reverse charger connection but we also need a circuit that will detect the issue and the MCU could be informed.

  • 0 in reply to Savvas Kokkinidis
    TI__Expert 3425 points

    Hi Savvas, 

    Please disregard my previous comment on the flyback, it seems I have misunderstood. 

    The circuit we recommend for reverse charger protection can be found in the bq76200 Reverse Voltage Considerations app note in section 3 High Voltage Reverse Voltage Techniques  on Figure 4.

    We also implement reverse polarity circuits in our monitor/protector family, namely the BQ769x2 reference designs and EVM. 

    To further supplement the understanding of this circuit please refer to the this app note: Multiple FET's with the BQ769x2 Battery Monitors  section 2 Reverse Charge Circuit  for a more in depth explanation on this protection circuit. I believe this circuit is something you can implement but please make note of the differences between the one used on BQ76200 vs BQ769x2 .  

    Unfortunately, there is no circuit implemented with our device that we can point to for the actual detection of the reverse charger event. 

    Best, 

    -Luis Torres