BQ40Z80: BQ40Z80 RSOC drop when use LiFePO4

Star Xu

Part Number: BQ40Z80
Other Parts Discussed in Thread: GPCCHEM

The customer mass production with BQ40Z80, The cell is LiFePO4. The problem is RSOC will drop from 100% to 69% - 73% after 5 hours placement.

If set LFP_RELAX=1, Whether RSOC jump problem can be improved.

Waiting for your reply.

Thanks

Star

over 2 years ago

0 Wyatt Keller over 2 years ago

TI__Guru** 105760 points

Hello Star,

LFP_RELAX should be used with LFP cells. What chem ID is being used?

Sincerely,

Wyatt Keller

0 Star Xu over 2 years ago in reply to Wyatt Keller

TI__Genius 9645 points

Hi Wyatt

There are two products, one product's CHEM ID is 0x0400, and the other product's CHEM ID is 0x0445, both of them all have the RSOC jump issue.

Thanks

Star

0 Wyatt Keller over 2 years ago in reply to Star Xu

TI__Guru** 105760 points

Hello Star,

If they do not have LFP_RELAX set it definitely should be. It will help prevent OCVs being taken in flat region causing jumps.

Sincerely,

Wyatt Keller

0 Star Xu over 2 years ago in reply to Wyatt Keller

TI__Genius 9645 points

Hi Wyatt

They have set the LFP_ RELAX=1, also set the RELAX_ SMOOTH_ OK=1, at this time, it jumps from 100% to 69% after 4-5 days.

Waiting for your reply.

Thanks

Star

0 Wyatt Keller over 2 years ago in reply to Star Xu

TI__Guru** 105760 points

Hello Star,

This is one of the main limitations of LFP type chemistries with such a flat voltage curve, everything needs to be optimized or there will be issues in estimation. I would definitely disable any of the relax smoothing or relax jump settings so the SOC doesn't jump during relaxation and the smoothing will have more time to adjust any jumps.

Please share the .gg file and the GPCCHEM report and data submitted.

Sincerely,

Wyatt Keller

Power management

Power management forum

BQ40Z80: BQ40Z80 RSOC drop when use LiFePO4