BQ27441-G1: SOC always at 100%

laurent sylvain

Prodigy 40 points

Part Number: BQ27441-G1
Other Parts Discussed in Thread: GPCCHEM

Tool/software:

Hi,

I'm using the BQ27441-G1A to manage this kind of battery : 56456 302 012

Battery characteristics :

rated capacity :2400mAh
Nominal voltage 3.7V
Watt-hour rate :8.9Wh
Max. charge voltage :4.2V
Max. continus Discharge current :2000 mA
Rec. Chareg cut off :23mA

I communicate with the BQ27441 with an STM32 microcontroler by sing I2C interface, and I haven't any issues with that.

My issue is that the µControler always read 100% for the SOC, while I put a battery at 40% or 70%.

The real SOC of the battery is read with an old electronic using a BQ27410.

To initialize the BQ, the µC write several parameters : Design Capacity (2400), Design Energy(8900), Terminate Voltage (3200), Hibernate_I (21), Hibernate_V (3000).

Just before reading the SOC, I read RemainingCapacityUnFiltered and FullCapacityUnFiltered. Both of them are equals and the SOC is 100%.

Reading Voltage, AverageCurrent and AveragePower are corrects.

My question is how the BQ calculate the RemainingCapacityUnFiltered and FullCapacityUnFiltered and then SOC ?

over 1 year ago

0 Diego over 1 year ago

TI__Mastermind 25665 points

Hi,

Did you get a ChemID match?

Did you complete a learning cycle?

This documentation answers your questions.

Theory and Implementation of Impedance Track Battery Fuel-Gauging Algorithm (Rev. A)

Regards,

Evan

0 laurent sylvain over 1 year ago in reply to Diego

Prodigy 40 points

Hi, thank you for your response.

1. When I read the ChemID, the BQ return 0x0000 and it's the same case for Device_Type, FW_Version ...
But Temperature, voltage and Current have good values.
To read the Control() registers, does it have to be in seal or unseal position ?

2. I'll read the documentation but I believed that by default the BQ could be return the SOC without learning cycle.
I am reading even the doc and I'll you a feedback on that.

Regards.

0 Diego over 1 year ago in reply to laurent sylvain

TI__Mastermind 25665 points

Hi,

1) Yes, the device needs to be unsealed. You need to get a chemID match by using the GPCchem tool before you will achieve an accurate SOC reading.

2) In order for the gauge to return a valid SOC reading you need to calibrate the gauge, use the GPCCHEM tool, and complete a learning cycle.

Regards,

Evan

0 laurent sylvain over 1 year ago

Prodigy 40 points

Hi,

1. Ok I'll try tomorrow morning by unseal the gauge before reading ChemID or other registers.

2. Are we agree that even if the gauge has not perform a complete learning cycle, it shouldn't return a SOC at 100% ?

In my application, I don't need a high accuracy.

sluuac9 Saïd : For many battery types and applications, the predefined standard chemistry
profiles available in the bq27441-G1A or bq27441-G1B fuel gauge are sufficient matches from a gauging
perspective

regards.

Sylvain.

0 Diego over 1 year ago in reply to laurent sylvain

TI__Mastermind 25665 points

Hi,

My mistake, this gauge has preprogramed chemistries, so the GPCCHEM tool is unnecessary.

But a learning cycle will need to be completed prior receiving accurate SOC reading.

Have you configured the gauge as seen in chapter 4 in the document linked. Quick Start Guide for bq27441-G1 (ti.com)

Regards,

Evan

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BQ27441-G1: SOC always at 100%