BQ40Z50-R1: BQ40Z50-r1 change the Term V from 3000mV to 3450mV, Qmax update fail

Hi Jose Couso

Thanks for your help.

1. 2023-01-03 Modify design cap 3950mAh to 2880mAh / Term V 3000mV to 3450mV / Reserve Cap-mAh 1550mAh

During charge the RSOC and RC did not update until voltage >3.7V, QMAX not update. 

2. 2023-01-04 Modify design cap 3950mAh to 2880mAh / Term V 3000mV to 3450mV

During charge the RSOC and RC update normal but QMAX not update. 

APP00379 DF10.rar

Whether the second method is feasible？

Thanks

Star

Hello Star,

There is a misunderstanding, please let me be more clear.

• Design Capacity should not be changed, it should always stay at the stated nominal capacity of the cell manufacturer datasheet.
• Reserve Cap - mAh should not be increased that much. In the app note example this was increased by few hundreds. For instance, start with 450 mAh. What this would do is report SOC = 0% when cell voltage is near 3400 mV. Simulations will still run with the Reserve capacity after SOC = 0%
  
  
• Please keep TermV at 3000 mV 
  
  
• Design voltage should be set to the highest charged voltage of the cell. 
  
  
• Qmax Cell0 should be left at the same last reported value when customer had the initial configuration. Please see below

  Star Xu said:

  It is normal to use BQ40Z50-R1 with 1S1P/4040mAh according to the normal learning procedure

  Again, these are trial errors, but I am sure that more accurate results will be obtained if Design Capacity is not touched and if increase Reserve Cap by few hundreds.
  
  Regards,
  Jose Couso

Hi Jose Couso,

1. Fully learning (4.2V to 3.0V),The Reserve Capacity is about 1550mAh ~ 1850mAh ( @Cell 3.4V ~ 3.0V )

2. Cell capacity (Typ. / Min.) = 4040mAh/3950mAh. so set Reserve-cap = 1550mAh

3. i will tyr again (condition : design cap = 3950mAh / Term V = 3000mV / Reserve Cap - 395mAh), But  when charge mode RSOC start at 3.7V 

hi Jose Couso,

The Same as I said RM delay calculation after charge, the cell Voltage up to 3.5V RM = 1mAh ( RSOC = 1%)

 APP00379-DF10-2023-01-09L.gg.csv2023-01-09_TI SET.rar

Hello Luke,

Please give me some time to run simulations on my end.

Also, has the 1s1p configuration changed? Please provide the configuration file that was working in the first place.

Regards,
Jose Couso

hi Jose,

Log data / GG file as attachment file.

2022-12-15.rar

B/R

Luke

Hello Luke,

Thanks for the files. I will work on it today or tomorrow,

Regards,
Jose Couso

Hello Luke,

I took a look at some of the data you shared, it's quite confusing reviewing since I think multiple topics are being brought up, I would recommend making a thread for each specific question you have otherwise we will not be able to provide the best suggestions.

From what I can tell there these are the questions:

Why there's no Qmax update when term V is lowered

Why RemCap delays when charging starts

It may be best to make a separate post for the RemCap discussion.

Can you share the chem ID number used regarding the Qmax issue? I would like to check the data.

Sincerely,

Wyatt Keller

hi Keller, Couso,

I'm sorry for bothering me, I understand that there are too many solutions during this time, I explain the test plan, the full charge/discharge study is the result is good, and follow-up tests based on this.

CHEM ID : 2052

solation:
S1. change term V 3000mV to 3450mV.
Result: The Qmax can`t updata. RM RM delay compute ( compute when cell high then 3650mV )

S2. customer suggest change Design cap 2880mAh ( all parameter changed ex: design energy...ect).
Result: Qmax can`t updata, Max error 100%, RSOC at 3.7V compute 1%. RM RM delay compute ( compute when cell high then 3700mV )

S3. Design cap 3950mAh, Term V = 3200mV, Reserve Cap - 395mAh(capacity 10%).
Result: Qmax can updata, 3450mV=1%, Discharging mode RSOC 3650mV compute, ( RM compute when cell high then 3500mV )

I think S3 is better, but I don't understand why the RM/RSOC calculation is delayed, is it because the discharge cut-off at 3000mV relationship causes a delay in RM/ROSC calculation?

Hello Luke,

If you take a look at the True FCC and True RemCap values in your log with delayed RSOC you will see that the actual remcap calculated by the gauge is actually negative. This means that you discharged below the terminate voltage. The gauge will always use the terminate voltage as the reference to calculate the RemCap. The reserve capacity is essentially just subtracted from this calculation. The reason you see the delay is because the filtered values won't start incrementing until the True RemCap goes positive again.

Sincerely,

Wyatt Keller

Hello Luke,

I'm glad you were able to resolve the issue.

Just a note on the terminate voltage, the reason we usually suggest the reserve capacity should be used is because when you move the terminate voltage up outside of the voltage "knee" it can be harder for the estimation for 0% SOC since the change in voltage per DOD is much less at high voltages. Past the knee the voltage moves rapidly down for each DOD point.

Sincerely,

Wyatt Keller