BQ40Z50-R2: Battery Assemnly Undercharge Issue - Unable to achieve full charge

Hi,

I just realized that the green means 0 and therefore not enabled. As a follow up to my question below, which setting determines when the charging will be stopped once a certain voltage is reached in each of the cells? In other words, how can I determine whether the charging will be stopped at 12.6 V and not a lower value to make sure this is not the issue?

Is this defined within the Advanced Charge Algorithm - Voltage Range table (please see below). The Charging Voltage High is currently set at 4000 mV. Does this mean the charging will be stopped once each cell reached 4000 mV?

Thanks in advance for you help.

Best regards,

Joe DeWitt

Hi Joe,

I believe the best way to go about ensuring that the gauge stops charging at a certain voltage is to us the Valid Charge Termination functionality. This is where the list of requirements below must be met for two consecutive 40s periods and complete the list of actions on the right. More about this can be found in the bq40z50-R2 Technical Reference Manual:

Also, if you send a bqStudio log file of the current charge cycle and the .gg file of the gauge settings, we can take a deeper look into it.

Regards,

Anthony

Hi Anthony,

Thank you for the response. It is much appreciated. I will request the bqstudio log file of the charge cycle and the .gg file from the factory as they have been performing the charge cycles.

In regards to the following calculation in the Valid Charge Termination Table you reference above, can you please confirm my understand of where these values are pulled from:

Max cell voltage 1...4 + Charge Term Voltage >= Charging Voltage() / number of cells in series 

Max cell voltage: Real values read from Cell 1 Voltage, Cell 2 Voltage and Cell 3 Voltage in the Registers Table and will be the sum of the individual cell values for the calculation.

Charge Term Voltage: User inputted value located in the Data Memory -> Advanced Charging Algorithm - >Termination Config table (see below which is 75 mV for my IC for each cell)

Charging Voltage(): Charging Voltage High value which is user inputted from the Advanced Charge Algorithm -> Voltage Range Table -> Charging Voltage High (see below which is 4000 mV for my IC)

Therefore, and assuming all the cells are at the same voltage, once the individual cell voltages are at 4000 mV - 75 mV = 3,925 mV and the other conditions specified in the Valid Charge Termination table are also met, the charging will stop.

Is this understanding accurate?

Thanks in advance for your support.

Best regards,

Joe DeWitt 

Hi Joe,

Joseph DeWitt said:

Max cell voltage 1...4 + Charge Term Voltage >= Charging Voltage() / number of cells in series 

Max cell voltage: Real values read from Cell 1 Voltage, Cell 2 Voltage and Cell 3 Voltage in the Registers Table and will be the sum of the individual cell values for the calculation.

Charge Term Voltage: User inputted value located in the Data Memory -> Advanced Charging Algorithm - >Termination Config table (see below which is 75 mV for my IC for each cell)

Your understanding of these values is correct.

Regarding this stopping the charge, this functionality can work in turn with the [TC] bit, which can be configured to turn the charge FET off as well:

Regards,

Anthony

Hi Anthony,

Thank you for the response.

Can you confirm whether the statement below is also true in addition to the statements you confirmed above:

Charging Voltage(): Charging Voltage High value which is user inputted from the Advanced Charge Algorithm -> Voltage Range Table -> Charging Voltage High (see below which is 4000 mV for my IC)

If not, please advise regarding where the Charging Voltage() value is taken from.

Best regards,

Joe DeWitt

Hi Joe,

You are somewhat correct. The ChargingVoltage() is the parameter set in the Advanced Charge Algorithm section multiplied by the amount of cells in the stack:

Regards,

Anthony

Hi Anthony,

Thank you for the additional clarification.

I noticed that for my battery assembly the Registers table is showing temperatures of 195.3 C for TS3 and 195 C for TS4 (please see below). Could this be causing the Charging Voltage () to be 4000 mV as reflected in the High Temp Charging table from the Advanced Charge Algorithm menu (see second attachment below)?

I did not want to use TS3 and TS4 so I connected 0 Ohm resistors from these BMS terminals to ground on the BQ40Z50 BMS. I think I may need to install 10 K ohm resistors instead in order to address these inaccurate temperature readings. 

Or does the BMS determine which Charging Voltage () to use based on the Int Temperature or Cell Temperature which are reading normal.

Thanks in advance for your support. 

Best regards,

Joe DeWitt

Hi Joe,

Joseph DeWitt said:

I noticed that for my battery assembly the Registers table is showing temperatures of 195.3 C for TS3 and 195 C for TS4 (please see below). Could this be causing the Charging Voltage () to be 4000 mV as reflected in the High Temp Charging table from the Advanced Charge Algorithm menu (see second attachment below)?

Can you please ensure that the TS3 and TS4 are disabled in the Temperature Enable Register? If these are enabled, then this can effect the temperature reading here.

Regards,

Anthony

Hi Anthony,

Below are the settings currently in place. I believe this disables TS3 and TS4 (green - 0 bit) and enables TS1 and TS2 (Red - high or 1 bit).

Best regards,

Joe DeWitt

Hello Joe,

Anthony is currently out of office. He should get back to you next week.

Regards,

Adrian

Hi Anthony,

Yes, that is correct. TS1 and TS2 are reading 22.6 C. I'm going to test charging the battery assembly with TS3 and TS4 disabled and see if we're able to get each cell to 4.2 V.

I appreciate all the support.

Best regards,

Joe DeWitt

Hi Joe,

Sounds good, please let us know if this is able to improve the results.

Regards,

Anthony