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When ltc6804 is applied to ltc6811 board, cell balancing problem occurs.

Category: Software
Product Number: LTC6804-1
Software Version: none

Hi manager,

Our customer used the LTC6811-1 for ESS and she is designing with LTC6804-1 becasue of delivery issue.

also, she did not change schematic and PCB and SW. 

as a results, cell monitoring is good until external cell balancing.

when external cell balancing is starting, cell voltage is changed over 300mV but EV kit of the LTC6804-1 did not change than working board.

could you please advise on what to consider?

external cell balancing)

- DCC mode

- external discharging rate : 60mA

- RC filter : 100ohm and shunt 100nF

- Filter mode : 7khz normal

- interface : 4 wire SPI without daisy chain

Best regards,

daejung.

before external cell balancing =======================================================================> after external cell balancing

  • hello,

    Can you let us know a when external cell balancing is starting, all cell voltages is decreasing 300mV or only balancing enabled channel ?  and in your screenshot am seeing there is  300mV drop in cell 10 path in both before and after.

  • Hi ChethanBM,

    when starts the cell balancing, 9ch is variated over 100mV and voltage level is increased as below table.

    If you have a e-mail address, I will send the LTC6811 code. 

    Could you please check FW code for LTC6804-1?

    LTC6811-1 balance head file => is able to use at LTC6804-1 ?

    #include "common.h"

    typedef enum
    {
    B_SEARCH, B_RUN, B_HUSE, B_STOP
    }BAL_STATE;

    typedef struct
    {
    BOOL bal_new_data;
    BAL_STATE bal_state ;
    u16 bal_buf;
    u16 bal_cnt;
    u16 highlimit;
    u16 lowlimit;
    }BAL_ST;


    #define BAL_ON_DIFFV 5
    #define B_PROGRESS_TIME 600
    #define B_HUSE_TIME 10
    #define B_ALL_OFF 0x0000

    #define B_STOP_TEMP 70

    extern void Init_Cell_Balance(void);
    extern void Cell_Balance_Control(void);


    #endif

     cell voltage deviation after cell balancing with LTC6811-1 FW code)

    ch Before cell balancing After cell balancing delta(before-after)
    1 3.9909 3.9907 0.0002
    2 3.993 4.0066 -0.0136
    3 3.9915 4.004 -0.0125
    4 3.9917 4.0066 -0.0149
    5 3.9935 4.0101 -0.0166
    6 3.992 4.0073 -0.0153
    7 3.9907 3.9907 0
    8 3.9918 4.008 -0.0162
    9 3.9922 4.0077 -0.0155
    10 3.6872 3.7051 -0.0179
    11 3.9917 4.0103 -0.0186
    12 3.9881 3.9879 0.0002
  • Hello,

    Seeing the results, the voltage isn't varying over 100mV ; its below 20mV. Did you measure it physically on board ?could you probe before and after LC circuits to measure voltages during Cell balancing (if you have access to measure) and please confirm are you seeing this behavior in RT ?