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BQ40Z80: Activation Process of BQ40Z80 device

Shubham Yadav
Intellectual 275 points
Part Number: BQ40Z80

Tool/software:

Dear Sir,

We have designed a BMS with 6s configuration with each cell can charge maximum up to 4.2 V resulting overall BAT voltage to 25.2 V. Now as these BMS is assembled in a battery pack I have certain doubt related to waking up the BMS in a pack. As, we are now designing a battery charger board to charge our battery pack, now suppose if my BMS goes in shutdown mode. I am providing 28v power to my battery charger board through a battery adapter for waking BMS. Now I am generating waking voltage for pack 25.2V by droping 28v through 4 series diode as shown in attached images and current limited to pack is 50mA through a series resistor. Now suppose, initially my battery Pack is shutdown  and I have connected the V_Pack terminal to my battery Pack+ terminal. So, voltage available at V_PACK terminal is 28V till my battery pack won't wake up. As soon as, my battery pack wakes up by these 28v  and if it demands currents then there will be drop of 0.7V across 4 diodes resulting voltage at my V_PACK terminal as changing from 28V 25.2 volts.

1) So, sir I want to know If I provide voltage at my pack 28V initially for waking up my BMS will it be OKK? If my bms wakes up and demands current then drop occurs and V_PACK changed to 25.2v. Will these sudden change from 28V to 25.2V will do any damage to my BMS?

I have attached image of battery pack voltage generation please refer it for your reference.

Waiting for your reply,

Thanks & Regards,
Shubham

  • 0
    TI__Mastermind 28450 points

    Hi Shubham,

    Can you please show us on the schematic where V_PACK is being attached?

    Is the battery sensing 25V the same as the Pack pin?

    Regards,

    Anthony

  • 0 in reply to Anthony
    Intellectual 275 points

    Dear Sir,

    This V_PACK is going to be connected to my BMS PACK+ terminal, and VCC_FILT = 28V.For waking up the BMS board inside the battery pack, we are connecting it to our battery charger board connector, where this V_PACK voltage is coming and getting connected to our BMS PACK+ terminal. Initially, when my BMS in battery pack is in shutdown mode and getting connected to our battery charger board connector, at that moment V_PACK=VCC_FILT=28V is getting applied to our BMS PACK terminal because no current is flowing through the diode and no voltage got dropped across the diode. As soon as my BMS inside the battery pack gets woken up by these 28 volts and  if the battery present in battery pack is slightly discharged, then it will demand current. At that moment, 0.7 volts will drop across each diode, and V_PACK gets changed from 28 volts to 25.2 volts. 

    So, sir my questions is
    1) Is it initially safe to apply 28v to my battery pack BMS for waking it up?
    2) As soon as, my BMS inside the battery pack gets waked up and if the battery demands current, then there is a change in V_PACK voltage. Will these sudden changes in V_PACK from 28V to 25.2 do any damage to my BMS?

    Waiting for your reply,

    Thanks & Regards,
    Shubham

  • 0 in reply to Shubham Yadav
    TI__Mastermind 28450 points

    Hi Shubham,

    I believe that if the battery is sensing the same voltage that is being seen on the Pack pin, then there should be no issue. Please allow me to get council with our team to confirm this for you.

    Regards,

    Anthony

  • 0 in reply to Anthony
    Intellectual 275 points

    Dear sir,

    Any update?

  • 0 in reply to Shubham Yadav
    TI__Mastermind 28450 points

    Hi Shubham,

    Is it possible to share the full schematic so we can get a better idea? Just to confirm, the biggest concern is whether the 28V being applied to PACK at this time is going to damage the device?

    Regards,

    Anthony