BQ40Z50: Full charge capacity jump

Radu Toma

Part Number: BQ40Z50

Hi there,

The BQ50Z50-R2 is used in our smart battery pack. The battery is a 14.8V (nominal voltage), 6Ah, (96Wh) 4S5P Li-Ion.

However we have noticed an odd behavior. When charging the battery, very seldom, the battery does not charge to 16.7V, which is the charge termination voltage set by our charger (see below). The charging is done via a "dumb charger", based on BQ24618RGET. Because of this, the charger keeps trying to charge the battery, instead of displaying that the charging is complete.
Please observe the drop in full charge capacity and remaining capacity. Also we noticed, while using the Battery Management Studio, that the T_ambient was reported as 3.9 deg C. This is also odd because the charging was done at room temperature. (Further the Lifetimes and Protections of the BMS do not indicate any issues.)

Looking forward for your comment!
Best regards,

over 6 years ago

0 Batt over 6 years ago

TI__Mastermind 42535 points

Your question has been assigned to an AE, you will receive a reply in 1 week or less.

0 Radu Toma over 6 years ago in reply to Batt

Prodigy 30 points

Thank you! Looking forward to some answers.

We have been able to reproduce the behavior above. Looks like it's relating to the valid charge termination conditions.

We have changed the "Charge Termination Voltage" from the default 75mV to 0 mv and this seems now that the battery is performing a little bit better.

My question would be: do we need to re-run a learning cycle?

Thank you!

0 Swaminathan Ramanathan75031 over 6 years ago in reply to Radu Toma

TI__Expert 6575 points

Hi,
Changing the operating voltage range for the pack i.e charge termination voltage or discharge termination voltage will not require you to re-run the learning cycle.
Regards,
Swami

0 Radu Toma over 6 years ago in reply to Swaminathan Ramanathan75031

Prodigy 30 points

Brilliant! Thanks!

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BQ40Z50: Full charge capacity jump