Cell Balancing Issue in MC33771C BMS Driver

[vardhan]

Hi,

    I followed the below steps to activate cell balancing on S32K144 EVK Board (AFE  MC33771A).

CBINDV_CELL_TIME=1; // Timer set for 1 minute
BCC_CB_Enable(&g_bccData.drvConfig, BCC_CID_DEV1, true); 
balancingStatus = BCC_CB_SetIndividual(&g_bccData.drvConfig, BCC_CID_DEV1, highestCellIndex,true, CBINDV_CELL_TIME); // Applied CB for highestCellIndex 9

We observed that all 14 CELLS MOSFETS are ON and could see the voltage across CB resistors (3.2v). As per the Datasheet only CELL 9 MOSFET should be ON.

 Is it the expected behavior please support to resolve this issue.

thanks

vishnu

[vardhan]

Hi JozefKozon,

                          Thanks for the reply  I have the MC33771B datasheet and also Just want to confirm that what are the cases
for getting all MOSFETS on at time when  applied Cell Balancing for individual cell.

thanks

vishnu

[JozefKozon]

Hi Vardhan Muvvala,

I have checked the MC33771B datasheet. If you want to balance only the cell 9, please set the CB9_EN bit in the CB_CFG_9 register to 1 and please make sure the other CBx_EN bits in CB_CFG_x registers to 0. The time for the Cell 9 can be set in the same CB_CFG_9 register, bits CB9_TIMER. Please refer to Table 53. in the datasheet.

With Best Regards,

Jozef

[vardhan]

Hi JozefKozon,

                          Thanks for the reply and I forgot to mention that we are using S32K144 board with MC33771B not MC33771A.so please let me know for the  solution for MC33771B driver .

thanks

vishnu

[JozefKozon]

Hi Vardhan Muvvala,

there is Cell terminal leakage diagnostics procedure in section 9.11 in the MC33771B datasheet. Do you have the MC33771B datasheet? All MC3377xx datasheets are confidential and you would need to have the NDA (Non Disclosure Agreement) signed with NXP to obtain the datasheets.

With Best Regards,

Jozef

[JozefKozon]

Dear Vardhan Muvvala,

I would recommend you to first perform Cell terminal leakage diagnostics to verify, if the cell voltage terminal or the cell balance terminal are not sinking or sourcing current and see if there isn't a hardware issue with the design. Please follow the instructions in the MC33771A datasheet, section 9.11 on pages 38, 39 and 40.

With Best Regards,

Jozef