BQ27621 - battery level jumps when plugged to charger and charging/discharging detection

Michael V

Part Number: BQ27621-G1
Other Parts Discussed in Thread: EV2400

Hello,

Here I have a two questions:

1) When I plug the charger to the board, BQ27621 shows battery level jumped to 30-40% (example: was 19% of battery, after plugging of the charging: 65%). When I unplug the charger, the battery values is starting go down (after minute-two 1% down), but when I restart the board, BQ27621 returns the previous (19%-20% value) - what can be a problem? Is it correct behavior?

2) When I connect the charger to the board, sometimes I get a changing of the flag DSG in the Flags() after about 10-15 seconds - what can be a problem?

Thank you very much!!

over 7 years ago

0 Onyx Ahiakwo over 7 years ago

TI__Guru* 76230 points

Hi Michael,
This device is a voltage based gauge and it relies on OCV measurements for SOC prediction. When you plug in the charger, does the voltage jump up significantly? Can you reduce the max IR correct in gas gauging of data memory from 400mV to 200mV so we see if that improves the situation.

For the issue of the DSG flag, what diid you set your Dsg I rate threshold to? pls check the TRM and the user guides on how to configure that for your application.

thanks
Onyx

0 Michael V over 7 years ago in reply to Onyx Ahiakwo

Prodigy 130 points

Hello Onyx and thank you very much for your answer!

I don't clearly understand how to write those values to the BQ27621. Do I need to unseal the device? When I did updated the values, do I need to perform the initialization process?

Where can I find the correct algorithm for writing data to BQ27621?

I have to say, that the documentation for the BQ27621, for programmers, is one of the worst that I saw :(

Thank you very much for your help!

0 Dominik Hartl11 over 7 years ago in reply to Michael V

TI__Guru 61536 points

For code examples, check out www.tij.co.jp/.../slua801.pdf

0 Michael V over 7 years ago in reply to Dominik Hartl11

Prodigy 130 points

Hello Dominik,

Thanks for the link.

Something I cannot understand...

I do all configuration according to the Quick Start Manual. In the block diagram that placed there I see the needed algorithm for the initialization and all registers/commands that I need to write.

UPDATE START:

Be careful! In the quick start manual init diagram I found a number of the mistakes!

Addresses of the data memory that should be read and write are wrong!

Please, see my question about it: question

UPDATE END

In the link that you posted I see different addresses (for example, address (class id) 81 for design energy and design capacity, but according to the Quick Start Manual it should be accessed by addresses 74 (0x4A) for Design Capacity and 76 (0x4C) for Design Energy). I don't understand which of addresses I should use! :(

In addition, I see that in the document from the link it's suggested to use the Battery Management Studio. I tried to use it, but without a lack. Could somebody send me a configuration file for the battery with the next parameters:

DESIGN_CAPACITY:                                      1450mAh
DESIGN_ENERGY:                                        DESIGN_CAPACITY * 3.7 = 1450*3.7 = 5365 (3.7 parameter - according to BQ27621 datasheet)
TAPER_RATE_USB_CHARGER:                 157
TERMINATE_VOLTAGE:                    3200mV
MAXIMUM_BATTERY_VOLTAGE                  4200mV

Thank you for your help and answers!