BQ27531-G1: the learning cycle does not start because update status is not set

user1365602

Part Number: BQ27531-G1
Other Parts Discussed in Thread: BQSTUDIO

Hello,

I try to do a learning cycle with the bq27531 on my own board. Therefore I use the bqStudio withe the BQ27GDK000EVM and conected both with my board. I used the application note SLUA903 and carried out all the steps described. But after starting the leraning cycle (sending IT Enable and Reset), the update status did not change. It remains still 0x00. Nevertheless, I started to discharge and charge the battery. Still no change in update status.

When charging, I also noticed that FC is not set. To verify this I started another charging cycle (Stopcondition: FC is set). The bit was also not set during the test. Taper current was reached and the Voltage was higher than charging voltage minus taper voltage. However, I do not know whether the capacity requirement has been met. There are two different explanations in SLUUA96A.

Chapter 6.6.1.:

"accumulated change in capacity>Min TaperCharge"

Chapter 6.10.1.2.2.:

"Accumulated change in capacity<Min TaperCapacity"

Maybe both problems / observations have the same cause. Do you know of any similar problems, can you help me, or do you have a suggestion to try or investigate?

Thanks,

Steve

over 5 years ago

0 Kang Kang over 5 years ago

TI__Mastermind 24870 points

Hello Steve,

That is a typo.

The correct one is > min taper capacity.

Can you attach a gg file and log file? FC bit needs to be set here. That's the easiest way to tell if full charge has been reached.

0 user1365602 over 5 years ago in reply to Kang Kang

Prodigy 50 points

Hello Kang,

Thanks for your reply.

I have only a gg file and log file for the charging cycle. I attached thes two files. I'm going to log the learning cycle as soon as possible.

(We use a Panasonic NCR18650B)

Thanks,

SteveLogFile_Charging.csv GG_File.gg.csv

0 Andy Liu (BMS) over 5 years ago in reply to user1365602

TI__Guru 52115 points

Hi Steve,

Let me know if you can provide a bqStudio log fo the entire learning cycle.

Andy

0 user1365602 over 5 years ago in reply to Andy Liu (BMS)

Prodigy 50 points

Hello everybody,

yesterday I started a new learning cycle. I used the alternative method. After the initial discharge, the battery relaxed for 5 hours. Then I send the "IT Enable" and the "Reset" command. (The update Status was still 0x00) After another short delay, I started the charging cycle. I used the GDK with the following settings:

Charge Voltage: 4200mV

Charge Current: 1000mA

Termination: Taper Current 55mA

After the Charging and a Relextime (over night) I stoppt the learning cycle, because the FC bit wasn't set.

I also added the Auto Export files from the Gauge Data Memory to the *.zip file.

I would be happy if you have a few suggestions for what else I can try to achive a successfull learnig cycle.

Thanks,

Steve

8662.Learning cycle.zip

0 Andy Liu (BMS) over 5 years ago in reply to user1365602

TI__Guru 52115 points

Hi Steve,

I see these settings in your gg file.

"Configuration","Charge Termination","Taper Current","65","mA"

"Gas Gauging","Current Thresholds","Chg Current Threshold","65","mA"

"Gas Gauging","Current Thresholds","Quit Current","40","mA"

According to our app note, these settings must meet the following condition.

Charge Term Taper Current > Chg Current Threshold > Quit Current

I would suggest you set the Taper Current to something like 75mA.

Andy

0 user1365602 over 5 years ago in reply to Andy Liu (BMS)

Prodigy 50 points

Hi Andy,

I changed the taper current to 75mA, as you suggested. I tested whether the FC bit is now set. But I have still the problem, that it's not set. I will attach you the log file and the "new" GG file.ChangedTaperCurrent.gg.csv ChargingToFull.log

Maybe you see something that I haven't noticed yet.

Steve

0 Andy Liu (BMS) over 5 years ago in reply to user1365602

TI__Guru 52115 points

Hi Steve,

Did you send IT_ENABLE to the gauge device? In your log file, the Control Status[QEN] bit is 0, which means the Impedance Track algorithm is not enabled.

Andy

0 user1365602 over 5 years ago in reply to Andy Liu (BMS)

Prodigy 50 points

Hi Andy,

I didn't send "IT_Enable". Before I started a whole time-consuming cycle, I wanted to test separately whether the FC bit is set. In my previous zip file, I have the log file from a learning cycle. there I set IT_Enable and the QEN is high. In my understanding, the FC bit should be set independently of IT_Enable. Or am I wrong? I'm going to start a complete learning cycle next week.

Steve

0 Kang Kang over 5 years ago in reply to user1365602

TI__Mastermind 24870 points

Hello Steve,

Learning cycle requires IT Enable which is QEN bit to be high.

When IT is enabled, that's when FC bit is checked I believe.

Power management

Power management forum

BQ27531-G1: the learning cycle does not start because update status is not set