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BQ78350: 4units parallel connection

Yuta Nishie
Genius 5750 points

Part Number: BQ78350
Other Parts Discussed in Thread: BQ76930, EV2400,

HI,

I have some questions. I would appreciate it if you could answer them.

 

1. Considering the following as 1 unit configuration, is it possible to use 4 units in parallel? And I would like to operate it as a battery of about 26V/12A.

Unit: BQ76930+BQ78350DBT+battery(8s1p: 3,000mAh)

 

2. Is there any problem with the following usage?

In the first unit, set the BQ78350DBT to "Discharge" via SMBUS and write. SMBUS interfaces with EV2400.

->Unplug the USB connector of EV2400 (meaning turn off the power of EV2400), connect EV2400 to the BQ78350DBT of the next unit and turn on the power. Then, set it to "Discharge" via SMBUS and write.

->This is done for all 4 units, and after that, discharge ON/OFF control is done by an external switch, and this is used as a battery system. (Current synthesis is done by ballasting with ORING)

3. If the above is possible, we would like to control discharge ON/OFF simultaneously for 4 units as the operation of the product. In this case, is it correct to understand that ON/OFF control by a switch is not necessary, and ON/OFF control by an external switch is no problem?

Best Regards,

Nishie

  • 0
    Genius 5750 points

    Hi,

    I am sorry for asking so many questions, but I would appreciate if someone could help me.

    Best Regards,

    Nishie

  • 0 in reply to Yuta Nishie
    TI__Mastermind 39525 points

    Hello,

    This question has been assigned within the team and will be reviewed and followed up with another application engineer when possible. In the meantime please attach any associated .log/.gg files associated with the projects

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Genius 5750 points

    Hi Alan-san,

    Thank you for sharing with the team.

    Could you give me a rough estimate of when you can get a response?

    I will also check with my customer about the .log/.gg file.

    Best Regards,

    Nishie

  • 0
    TI__Guru 70846 points

    You can use 4 in parallel from a gauging perspective but you will have to be careful about currents between packs with different level of charge. The gauge will not control this and there is a potential for excessive currents if every pack is enabled.

    Do you mean "send a command to turn on the DSG FET" when you say "set the BQ78350DBT to "Discharge" via SMBUS"?

    If so, direct FET control is possible but it will effectively disable the protector and relies on the host uC for protection. It's also not available in sealed mode because it's intended for testing purposes.

  • 0 in reply to Dominik Hartl11
    Genius 5750 points

    Hi Dominik-san,

    I apologize for my insufficient explanation.

    I assume the following connection method.

    1. In preparation for this, set the EV2400 to discharge via the SMBus 1 unit at a time (send a command to turn on the DSG FET). After setting, it is always in the discharge state, and the physical switch and ORing IC control the voltage/current by turning on/off the connection with the load.

    2. I think the BQ78350 has 4 addresses. When setting the discharge, do I need to prepare a different address for each IC to communicate? I would like to be able to turn on/off 4 units at the same time, so I would be happy if the software control could be eliminated.

    Best Regards,

    Nishie

  • 0 in reply to Yuta Nishie
    Genius 5750 points

    Hi Dominik-san,

    I would appreciate your reply.

    Best Regards,

    Nishie

  • +1 in reply to Yuta Nishie
    TI__Guru 70846 points

    Can we consolidate this into one E2E thread?

    You have to use a separate I2C address for each bq78350 (which you can set with resistor dividers for each gauge). And then you must send the on/off command to each I2C address/gauge. This cannot be done with just one address.