BQ27421-G1: SOH read and Qmax update

Terry Wu2

Part Number: BQ27421-G1
Other Parts Discussed in Thread: BQSTUDIO

Hello Sirs,

Would you help on these questions ? TKS !

1. SOH read
Command is 0x20, reading two bytes, the lower eight bits are SOH percentage, and the upper eight bits are SOH status.
Currently reading 0x15a, indicating SOH status is 0x01, SOH percentage is 0x5a (90%).
Is this correct?

2. Qmax Update
In ba27421-g1-user_guide, there is a timing to mention Qmax Update. When there is a battery access, the first Qmax Update is triggered.
If the battery of ba27421-g1 is provided by battery, does it still recognize the access event of the battery? That is to say, battery access is first, and bq27421-g1 power on is the latter case.

3. Temperature report

bq27421-G1 can return temperature
Is there any protection for the charge/discharge temperature?
Or is he only returning the temperature??

over 6 years ago

0 Onyx Ahiakwo over 6 years ago

TI__Guru* 76230 points

Hi Terry
1. Yes that sounds right. I would encourage you to use bqstudio for configuration and evaluation of the gauge before implementing in your system. That way you have a good reference point for comparison purposes
2. I am not sure I understand what you are asking here. qmax updates occur after there has been 37% passed charge and two relaxation periods before and after the passed charge. It is not an instantaneous occurrence.
3. No, this gauge does not protect against over temperature.

thanks
Onyx

0 Terry Wu2 over 6 years ago in reply to Onyx Ahiakwo

Expert 2110 points

Hello Onyx,

About Q2, because we found this in bq27421-user_guide:

The [QMAX_UP] bit in the Control() register can be checked by the host to see if there has been a Qmax
update. The [QMAX_UP] bit is set on the first Qmax update after a reset or battery insertion event.

0 Onyx Ahiakwo over 6 years ago in reply to Terry Wu2

TI__Guru* 76230 points

Hi Terry,
What that means is that the flag will be set after a battery has been and the qmax conditions for an update has been met. it doesn't mean just inserting a battery will trigger a qmax update.

thanks
Onyx

0 Terry Wu2 over 6 years ago in reply to Onyx Ahiakwo

Expert 2110 points

Hello Onyx,

Understand and thanks~

Would you pls help below ?

1) When the SOH status (0x21) value is 0x02, can the SOH percentage (0x20) read indicate the current battery SOH?
2) Under what conditions will the SOH status value become 0x03? We did the experiment on EVM +bqStudio and have not found it to be 0x03.
3) QMAX_UP bit in Control status, under what conditions will it become 1? We experimented with continuous discharge (or continuous charging) of more than 37%, and did not change 1.

TKS~

0 Onyx Ahiakwo over 6 years ago in reply to Terry Wu2

TI__Guru* 76230 points

Terry

You need to have a two relaxation periods and passed charge of atleast 30%..
To get a qmax update, charge to full, relax two hours, discharge to empty, then relax 3 hours.
if the default chem id that come in the gauge is a close match, then you will have qmax and resup flags getting set and then at that point you can now review SOH flags.

thanks
Onyx

0 Terry Wu2 over 6 years ago in reply to Onyx Ahiakwo

Expert 2110 points

Hi Onyx,

Thanks your help !

When bq27421 exited from hibernation state due to I2C access, how could we get it back to hibernation?

Will it enter hibernation mode automatically ?

Thank you~

Power management

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BQ27421-G1: SOH read and Qmax update