BQ40Z50-R2: RSOC CAPPING BELOW 100%

Hi Jonathan,

Would you happen to have a log file depicting one of the degrading cells? There is a chance that the cells are degrading, however the FCC calculation should counteract this and allow for the SOC to still reach 100%. What is the SOH being reported?

Regards,

Anthony Baldino

Hi Anthony,

I will prepare this log file for you tomorrow when i'm in the office !!

The SOH for both packs are 100%,what are the different factors that can affect cells ?

furthermore how does one interpret logs ?

i struggled to read them as they look like they're in hexadecimal format, what do we look for?,

if you can use the above screenshot as a run through for me to understand them please

Regards

Jonathan Kabangu

Hi Jonathan,

Thank you for the update, please send the logs when they are ready.

I think the best way to intemperate the log file is to input the data to excel and use "Text to Column" to format the data, which will make it much easier to process. From there, the Hex values can be converted to binary, which will represent which bits are on and off in their respective registers.

Regards,

Anthony Baldino

HI Anthony,

i have got 2 logs from a pack that is capping below 100% with COV bits triggering 

Pack:012U:

012U-02.log

Pack 002V:

002V-01.log

Regards

Jonathan Kabangu

Hi Jonathan,

Thank you for sending those files. Looking into them, you can see at sample point #347 the COV protection is being triggered due to Cell Voltage #3 being over the COV protection threshold.

I believe at this point as well, the RSOC is being reported as 89%. Looking into the calculated Full Charge Capacity, it seems like the gauge is greatly overestimating the capacity of the cell compared to the design capacity. FCC at this point is 3927 mAh when your stated design capacity is 3200mAh.

How was the chemID chosen for this gauge? Was the GPCCHEM tool used?

Regards,

Anthony Baldino

Hi.Anthony,

I see at point #347 the cells are looking like this:

• Why is cell 3 in a higher voltage than the rest ,is there any evidence for this in the logs?
• cell 3 is the recovery stage since the protection is set at 3750mV, at point #346 cell 3 was at 3773mV which is above 3750mV(Protection threshold)

• Yes the RSOC is 89%at that point,what is the formulae for for full charge capacity? or at least how does the gauge do this calculation?
• Full charge capacity is 3927 mAh and remaining capacity is 3472 mAh
• I will reach out the supplier for the ChemID selection?
• My main question here is why is the cell 3 reaching high voltages before the other cells, is this a balancing issue?

Here's the gg file:

012U.gg.csv

Regards

Jonathan Kabangu

Hi Jonathan,

It seems like cell 3 has a greater voltage for the majority of the log. This could be a balancing issue.

Jonathan Tshimama-Kabangu said:

• Yes the RSOC is 89%at that point,what is the formulae for for full charge capacity? or at least how does the gauge do this calculation?

The full formula for FCC can be found in section 2.6 of the document below:

https://www.ti.com/lit/an/slua364b/slua364b.pdf?ts=1721322704659 

Jonathan Tshimama-Kabangu said:

I will reach out the supplier for the ChemID selection?

Thank you, this will give us a better idea of why the FCC could be overestimating.

Regards,

Anthony Baldino

Hi Anthony,

I will get those details for you!!! 

• i had a question in regards to the charging voltage & charging current , we see charge current as the pack charges all the way to 100% and this value changes and goes below <300mA but as for charge voltage there's no parameter for this showing how it changes  whilst were charging and how it goes below 100mV ,you know where i can find this?

i say this because the current is changing as the pack reaches 100% so the current gradually falls but i do not see the voltage falling especially if it needs to drop below 100mV at Charge termination?

Regards

Jonathan Kabangu

Hi Jonathan,

For Valid Charge Termination, all of the conditions need to be met for at least 2 consecutive 40 second periods.

In the picture above, it seems like the Voltage (~13500mV) + Charge Term Voltage (100mV) is not greater than the charging voltage (14000mV).

Regards,

Anthony Baldino

Hi Anthony,

• There's a few conflicting terms in the gauge ,if you can please help me understand the difference between 

1. Voltage?
2. Vpack?
3. Vbat?
4. and to add for VCT conditions which one of this voltage is it monitoring?

• for the packs with missing VCT,i think the main culprit is the COV triggering therefore one of the conditions not being met especially "the max cell voltage + charge term voltage> charge voltage ,what's your take on it :) 

Regards

Jonathan Kabangu

Hi Jonathan,

Voltage - The combined voltage being read from each of the individual cells. Typically reflects the total value.

Vpack - The voltage being read from the PACK pin of the device.

Vbat - The voltage being read from the BAT pin of the device.

For VCT, I believe the value being used for the condition is the largest value between the Cell 1 Voltage, Cell 2 Voltage, Cell 3 Voltage, or Cell 4 Voltage for the comparison.

This could be the condition that is not allowing the device to clear VCT, however it could also be the timing since two consecutive 40 second periods must be cleared.

Regards,

Anthony Baldino

Hi Anthony,

Just in regards to the RSOC capping at below at 92%,88% which is obviously due to COV triggering cause one of the cells hitting 3750mV and disabling charge 

could this be a balancing issue ?

Regards

Jonathan Kabangu

Hi Jonathan,

I still believe the RSOC capping early could be being caused by how the chemID was selected for this cell. The Design Capacity of the cell in use is 3200mAh, however the gauge is overestimating this value and making the Full Charge Capacity above 3500mAh. Please let us know how the ChemID was created when possible.

Regards,

Anthony Baldino