BQ40Z50: BQ40Z50: Battery Gauge : RemCap > Design Capacity

jhseos

Prodigy 30 points

Part Number: BQ40Z50
Other Parts Discussed in Thread: BQ24610

The Design Capacity of BQ40Z50 is 13,000mAh.

RemCap (Remaing Capacity) and FCC (Full Charging Capacity ) were less than 12,000mAh.

When I raised the charging voltage, sometimes RemCap and FCC exceeded 13,000mAh.

After VCT flag, the BQ40Z50 adjusts the RemCap and FCC below 13,000mAh.

Question :

Is it problem if RemCap and FCC are higer than Design Capacity ?

Does it okay if it is compensated ?

System
- Battery Gauge : BQ40Z50.
- Battery : 2S3P, 14,700mAh.
- Charger : BQ24610.

over 2 years ago

0 jhseos over 2 years ago

Prodigy 30 points

Charging Voltage : 8.28 V → 8.35V

0 Wyatt Keller over 2 years ago in reply to jhseos

TI__Guru** 105770 points

Hello,

Design Capacity is a programmed value, it is fine if the FCC is over the Design Capacity. If the FCC is over the Qmax that could indicate issues. Usually design capacity from the cell spec is a little conservative.

Sincerely,

Wyatt Keller

0 jhseos over 2 years ago in reply to Wyatt Keller

Prodigy 30 points

What are the issues with Qmax?

Is it a simple flag or a problem?

Design capacity : 13,000mAh, Qmax Cell 1 : 15596mAh, Qmax Cell 2 : 15496mAh, Qmax Pack ; 15496mAh.

I know that Qmax is updated.

In our battery system, 15496mAh was updated to 15511mAh.

When Qmax is below 13,000mAh, is it possible that RemCap > Qmax ?

I wonder if BQ40Z50 prevents this.

What seetings can I check for that?

thanks.

+1 Wyatt Keller over 2 years ago in reply to jhseos

TI__Guru** 105770 points

Hello,

I would not be concerned unless it is happening in your system. From the values you shared FCC is not higher than Qmax.

As Qmax decreases, FCC and RemCap will decrease but this will take many hundreds of cycles to get the Qmax to decrease from 15500mAh to 13000mAh.

I would review out Impedance Track collateral for more information on the algorithm: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1100653/faq-impedance-track-faqs

Sincerely,

Wyatt Keller

0 jhseos over 2 years ago in reply to Wyatt Keller

Prodigy 30 points

Thanks for your advise.

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BQ40Z50: BQ40Z50: Battery Gauge : RemCap > Design Capacity