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EM1402EVM: Balancing issue with 5A balancing current

Radhika Ballal
Prodigy 190 points
Part Number: EM1402EVM

Hello,

I have a battery pack of 13 Li-NMC cells which I am trying to balance using EM1402 board. I have made the required changes in the EVM sample code . I am able to balance the cells at 2A, 3A, and 4A balancing current but when I use 5A  as the balancing current. I am able to see the balancing current in more than one cell channel .

My 11th cell needs balancing , then I am able to see to balancing current in 12th as well as 6th cell .and this pattern is not fixed , any two cells (excluding the actual balancing cell) reflect the balancing current out of which one is charging and other is discharging with the same value of current as I am setting through my code.  I am measuring the current using current probe. Can you please suggest any solution to this problem ?

  • 0
    TI__Genius 10785 points

    Hi Radhika,

    You are using same hardware and software. No issues until you increase Current to 5A.

    6th cell FET is turned on by itself. Am I right?

    Can you do this?

    Start from 4A and increase the current and monitor channel 6 FETS.

    This is little unusual and we need to debug this.

    roger

  • 0 in reply to Roger Hwang
    Prodigy 190 points

    Hello Roger,

    Sorry for the late reply .

    The channel 6 is not fixed, it depends upon which cells need balancing. Also ,now I am getting the same issue with 2A, 3A or any balancing current for that matter.

    I tried balancing the cells with 2A current but still it shows balancing on some other channel , including the cell which needs balancing.

    I am trying to check the SOURCE and GATE voltages of individual channels .Will let you know if I find any progress.

     

  • 0 in reply to Radhika Ballal
    TI__Genius 9411 points

    Hi Radhika,

    Ok. Let us know what you find out and if you need further help.

    Regards,

    Leslie

  • 0 in reply to Leslie Marquez
    Prodigy 190 points

    Hello Leslie,

    When I checked the SOURCE and GATE pulses they all are coming accurately. So, then I checked the code and found that the channel no that needs balancing is changed continuously because the channels holding the cells have approximately same voltages. ( 3.169v, 3.171V) because of which switching was going on between these two channels . But the code that I have used is same as that of the example code. So, it would be really helpful if you could help me with solving this error in the code.

  • 0 in reply to Radhika Ballal
    TI__Genius 9411 points

    Hi Radhika,

    Are you referring to the EM1402EVM example code? If so, please take a look at the code inside the "do while" loop in the sys_main.c file. This "do while" loop looks for the cell that needs balancing, then balances for 1s, stops balancing, waits for 3s and then goes back again to find the cell that needs balancing. If you don't want this behavior you can modify this loop to satisfy the needs of your system (e.g. you can add a condition to not switch cells until you reach a desired voltage on the cell that you are balancing, or you can add a condition to only switch to balance another cell if the difference between those 2 cells is X value). 

    Best regards,

    Leslie