BQ34Z100-G1: Stops taking OCV measurements after a time

James Foster1

Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQSTUDIO

Hi,

We have succesfully gone through a learning cycle and Update Status is 0x6.

A few cycles after the learning cycle was complete, OCV readings stopped being taken and QMAX & DOD values stopped updating, with their respective counters just increasing above 100hrs even though we cycled the cells multiple times.

My assumptions is that OCV readings should occur every time the fuel gauge enters relax?

Interestingly when we reset the fuel guage and then do a few cycles OCV readings do occur for the first few times. Then they stop again.

Why would this be happening? Is it normal behaviour? Will the fuel gauge decide to take readings after 200hrs or somthing?

Thanks

James

over 5 years ago

0 Kang Kang over 5 years ago

TI__Mastermind 24870 points

Hello James,

Can you show me the test using a bqStudio log file?

0 James Foster1 over 5 years ago in reply to Kang Kang

Prodigy 180 points

Hi,

It is very difficult as the fuel gauge is floating at high volts.

I can give you all the register values if that helps?

But I think it easiest first to answer my initial question, should the fuel gauge take OCV measurement and update DOD/QMax on every cycle? Or does it only do it every 10 cycles or something?.

Thanks,

James

0 Kang Kang over 5 years ago in reply to James Foster1

TI__Mastermind 24870 points

Hello James,

OCV measurements are taken when the stack voltage reaches a dv/dt condition of < 1 uV/s.

It does not do it via cycle count.

0 James Foster1 over 5 years ago in reply to Kang Kang

Prodigy 180 points

Hi Kang,

Ok, thanks. Any ideas why it would take a few OCV readings after a reset and then never take any more?

Would it be helpful to do a charge to 100% then turn off the charger and begin the bqstudio log file? All it will show is no OCV measurement is ever taken.

Or would you like the register values?

We have a second unit programmed with the golden file from the 1st unit and it does the same thing.

Thanks

James

0 Kang Kang over 5 years ago in reply to James Foster1

TI__Mastermind 24870 points

Hello James,

It depends on how stable the voltage is and whether or not IT is enabled.

Yes, I think you should log a bqStudio file for us. I would like to look at the voltage and a few other debug registers such as DOD0. bqStudio logs all these by default.

0 James Foster1 over 5 years ago in reply to Kang Kang

Prodigy 180 points

Hi Kang,

I have attached the log file. I started it a few minutes after full charge was reached. It ran overnight and no DOD0 or Qmax updates were seen.

Our system is 16 x 100Ah 3.2V LIFEPO4 cells in series

I notice that the voltage fluctuates by one ADC sample which equals 16mV for our system (16 cells in series). This can't be the issue can it?

Cheers

James

0 James Foster1 over 5 years ago in reply to James Foster1

Prodigy 180 points

log after charge 4-14-20.zip

0 James Foster1 over 5 years ago in reply to James Foster1

Prodigy 180 points

Hi Kang,

Do you need me to collect any more information?

We are almost ready to release our product and this is holding us up.

We would really appreciate some help

Thanks

James

0 Kang Kang over 5 years ago in reply to James Foster1

TI__Mastermind 24870 points

Hello James,

Thank you for the log files.

Can you send me the bqz file you are using in bqStudio?

The default directory is C:\ti\BatteryManagementStudio\config\

We may need to open up a parameter for you to modify.

If it is the default bqz, just let me know.

0 James Foster1 over 5 years ago in reply to Kang Kang

Prodigy 180 points

2728.0100_0_16-bq34z100G1.zip

0 James Foster1 over 5 years ago in reply to James Foster1

Prodigy 180 points

See above for file, it is the default downloaded from TI website.

We have found that DOD readings are taken when discharged and rested. Also if we fully charge (beyond what gauge says is 100%) then DOD readings are taken.

But it seems no Qmax updates are happening still

0 James Foster1 over 5 years ago in reply to James Foster1

Prodigy 180 points

Correction, it seems if we fully charge (beyond 100% SOC according to guage) everything works fine and a Qmax update has occurred.

So is there a reason why DOD0 updates dont happen when cell is at 98% SOC after a charge? Is it because the voltage curve is so flat at this point?

0 Kang Kang over 5 years ago in reply to James Foster1

TI__Mastermind 24870 points

Hello James

I did look at the files.

We need to get a qualified DOD point. The log file you have shows a fairly flat voltage curve.

I think there is another DOD0 update when FC is set. What is the voltage divider setting here? Can you send me the gg.csv file so I can take a look?

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BQ34Z100-G1: Stops taking OCV measurements after a time