BQ76940: single solution for 24V and 48V battery pack

deepak naiknavare

Part Number: BQ76940
Other Parts Discussed in Thread: BQ76952, BQ76907, BQ34Z100

Tool/software:

I am trying to find a single solution for 24V and 48V battery pack.

I have considered BQ76940 and BQ76952 for this solution, but combined solution for both type of batteries looks difficult.

BQ76940 supports minimum of 9 cells so 24V solution would not be feasible with single AFE.

BQ76952 supports 3 to 16 cells but would need another solution to short the unused pins for 24V pack.

Would it be a good idea to use stackable solution with 2*24V battery pack =48V and configure to single for 24V where required.

1. Do you have any soutions for above configuration?

2. I would require atleast 5-6 48V packs in parallel to provide the required current, so using same solution for parallel should be possible with replication?

Let me know your feedback, if possible with part number or reference design.

Thanks,

over 1 year ago

0 Luis Torres over 1 year ago

TI__Expert 3425 points

Hello Deepak,

Our normal support team is OOO until tomorrow so I will try to help answer your question.

If you are asking about a single chip that can be used for both 24V and 48V without the need for a board change then that may be a challenge (dual footprint maybe?).

We do have the BQ76907 monitor that you may be able to stack. This would provide from down to 2s to 7s with a single IC but the abs max will need to be considered when stacking. I'd imagine that the BQ769x2 family stacking reference design may be useful in applying it for the BQ76907.

Here are the relevant links for stacking: Technical Article: https://www.ti.com/lit/pdf/sszt191 & Reference Design: https://www.ti.com/tool/TIDA-010247

Best,

-Luis Torres (PME)

0 deepak naiknavare over 1 year ago in reply to Luis Torres

Prodigy 230 points

Thanks Luis.

We have changed the requirement to 15s2p (only 48V) to boost the current requirement.

Do you see any issues in the above concept? We have requirement of 48V, 20A battery BMS.

+1 Luis H. S. over 1 year ago in reply to deepak naiknavare

TI__Mastermind 42070 points

Hello Deepak,

That looks okay. But have you considered using the BQ769x2 and BQ34Z100 instead? The BQ769x2 has integrated high-side FET drive.

Best Regards,

Luis Hernandez Salomon

0 deepak naiknavare over 1 year ago in reply to Luis H. S.

Prodigy 230 points

Yes i have considered the BQ769x2 and BQ34Z100 . But i have not done the calculations for the required worst case balancing current, so wanted the flexibility using external FETs to support fast charging as we would need more current balancing.

Do you have any application note to explain the cell balancing worst case current calculations?

0 Luis H. S. over 1 year ago in reply to deepak naiknavare

TI__Mastermind 42070 points

Hello Deepak,

The BQ769x2 should be able to handle higher balancing currents. It also supports external cell balancing.

The following application note goes over cell balancing with the BQ76952:

Cell Balancing With BQ769x2 Battery Monitors

Best Regards,

Luis Hernandez Salomon

Power management

Power management forum

BQ76940: single solution for 24V and 48V battery pack