BQ76920: Parallel battery packs

Lucas Bagrowski

Part Number: BQ76920
Other Parts Discussed in Thread: BQ78350

Hello, I am currently designing a Li-Ion battery pack, I a have a question about parallels packs and the BQ76920.

I want to make 4 packs of 5-s each (with 4 BQ76920) and put them in parallel, not a single one 5s4p with just one BQ76920, is that possible ?

Thanks

over 4 years ago

0 Luis H. S. over 4 years ago

TI__Mastermind 42900 points

Hello Lucas,

Would you mind sharing a diagram of how you plan to set-up this BMS? The BQ76920 also requires an MCU or the BQ78350 companion gauge to properly function. You probably will not be able to communicate with each IC using a single MCU as these would share the same I2C address.

I'd be concerned in the functionality of the protections if you plan to use it as a 5s4p system. If that is the plan, I'd recommend you stick with a single IC with 5s4p configuration.

Best Regards,

Luis Hernandez Salomon

0 Lucas Bagrowski over 4 years ago in reply to Luis H. S.

Prodigy 120 points

Hello Luis,

Thanks for your answer, yes of course I can, here is my schematical diagram:

I didn't add the BQ78350 on it but I know that I need one or more of them.

I am planning to use this configuration in order to avoid the capacities issues that may occure on one cell and disturbing those around if 4 are in parallel.

Best regards,

Lucas Bagrowski

0 Luis H. S. over 4 years ago in reply to Lucas Bagrowski

TI__Mastermind 42900 points

Hello Lucas,

This e2e thread may be helpful: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1042590/bq76940-question-about-parallel-stacks

If it's used solely for voltage monitoring, it should be okay. If you are using the BQ78350 for gauging features, I am not sure how this would function exactly, a sense resistor is needed for the gauging. This configuration was not in mind when designing the devices. So I am not sure if there would be unintended issues.

Best Regards,

Luis Hernandez Salomon

0 Lucas Bagrowski over 4 years ago in reply to Luis H. S.

Prodigy 120 points

Hi Luis,

So I think I will try to add ideal diodes between my different packs. Thanks for sharing the link.

Also I know that I need sense resistors, I didn't put them on my scheme to save time.

Thanks a lot for your answers.

Have a nice day

Lucas

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BQ76920: Parallel battery packs