BQ27441-G1: Coulomb counter for 0R500 ohm sense

Marvn Arcangel

Part Number: BQ27441-G1

Hi Team,

A customer esed bq27441G1A with a shunt resistor of 0R500 and is asking how to calibrate the Coulomb counter, In the BMS Software, there isn't any way to do this. the parameter "CC Offset" can't be set lower than 0.1.

Here is the scenario:

Shunt Resistor = 0R500, The load is set for battery consumes about 20mA.

In Battery Management Studio the Coulomb Counter goes too fast and thinks that the load consumes about 3280mA.

How can they calibrate the fuel gauge correctly?

Thanks!

Regards,

Marvin

over 3 years ago

0 Dominik Hartl11 over 3 years ago

TI__Guru 62006 points

You can scale the default CC Gain factor by 1mOhm/0.5mOhm = 2.

0 Marvn Arcangel over 3 years ago in reply to Dominik Hartl11

TI__Genius 12575 points

Hi Dominik,

Thank you for the response. However, the customer has a resistor of 500mOhm, and if they applied that equation is like:
1mOhm/500mOhm = 0.002

And the CC Gain doesn't admit a value less than 0.1.

Regards,

Marvin

+1 Dominik Hartl11 over 3 years ago in reply to Marvn Arcangel

TI__Guru 62006 points

In this case, you may have to use current scaling: www.ti.com/.../slua792.pdf

0 Ruben Artero over 3 years ago in reply to Dominik Hartl11

Prodigy 65 points

Please, check this part number: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1123002/bq27441-g1-coulomb-counter-offset-when-scaled-data

Could you help me?

0 Dominik Hartl11 over 3 years ago in reply to Ruben Artero

TI__Guru 62006 points

What is the specific question?

0 Ruben Artero over 3 years ago in reply to Dominik Hartl11

Prodigy 65 points

Can you read it?
I ask about the error of fuel gauge, the AverageCurrent() has a very big error with scaled data.

0 Dominik Hartl11 over 3 years ago in reply to Ruben Artero

TI__Guru 62006 points

The gauge will automatically calibrate for offset (internally, when the conditions are right for sleep mode). So what's left is to calculate the CC Gain value correctly.

* read the old CC Gain value
* apply a known constant current
* read the measured current (make sure the averaging filter has settled)
* calculate a new CC Gain = Old CC Gain * scaling factor * known current / measured current
* write the new CC Gain to the data memory (CC Cal class)

0 Ruben Artero over 3 years ago in reply to Dominik Hartl11

Prodigy 65 points

Okey, thanks!

I think this comment resolve my issue.

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BQ27441-G1: Coulomb counter for 0R500 ohm sense