BQ20Z655-R1: Balancing Start Value(mV) and Balancing End Value (mV)

Ugur Bak

Prodigy 160 points

Part Number: BQ20Z655-R1
Other Parts Discussed in Thread: BQ40Z50-R2

I'm using BQ20Z655-R1 for my 4S-3P battery pack configuration. BQ20Z655-R1 can monitoring, balancing etc.

I have to know balancing start value (deltaV between cells) and balancing end value. ( For example 150mV for start and 50mV for ending.) How can I learn?
If there are default values for balancing start and end values. How can I change it? I can do something on data with SMBus. Which part of programming can change this value?

Thank you.

over 7 years ago

0 David Hien over 7 years ago

TI__Genius 10830 points

Hi Ugur,
One of our BMS experts has been assigned to your issue and will answer shortly.

Regards,
David

0 Ugur Bak over 7 years ago in reply to David Hien

Prodigy 160 points

Hi David Hien,

I am waiting.

Thank you.

0 Ugur Bak over 7 years ago in reply to David Hien

Prodigy 160 points

Hi David Hien

Do you have any idea for this question?

Thank you.

0 Batt over 7 years ago in reply to Ugur Bak

TI__Mastermind 42535 points

Hi Ugur,

Cell balancing is enabled during chg. It is determined by a DOD delta which is calculated off of Qmax and the Min Cell Deviation in the dataflash. You don't have a minimum start or end voltage for that.

0 Ugur Bak over 7 years ago in reply to Batt

Prodigy 160 points

Hi Batt,

How can I calculate these values? Qmax / Min Cell Deviation, isn't it?

0 Batt over 7 years ago in reply to Ugur Bak

TI__Mastermind 42535 points

Hi Ugur,

Yes, superficially you are right. But the calculation is a bit more complicated than that as it involves fw quantization of charge. So, the calculation you said won't work directly as the units are different.

0 Ugur Bak over 7 years ago in reply to Batt

Prodigy 160 points

Hi Batt,

1. Our goal is to start balancing when the voltage deviation is more than 50mV. What can we do about it?

2. Is there any document about this issue? We are planning to set the data.

3. Do you have any advice about balancing with this IC? (Documents, etc.)

Thank you.

0 dMax over 7 years ago in reply to Ugur Bak

TI__Genius 14985 points

Hi Ugur,
First, have you considered using a newer gauge, such as bq40z50-R2?
Also, I must clarify that these gauges which use the Impedance Track algorithm do not perform cell balancing based on the difference in cell voltages but rather using the differences in capacities and states of charges between the cells. This is a superior method but somewhat more complicated. You can read more about cell balancing of bq20zXXX devices in this application note: www.ti.com/.../slua340c.pdf

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BQ20Z655-R1: Balancing Start Value(mV) and Balancing End Value (mV)