This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

EM1402EVM: Eliminating the external isolated 12 V required in the EM1402EVM

Part Number: EM1402EVM
Other Parts Discussed in Thread: BQ79616-Q1

Hi.

1. It says in another TI support "The EM1401EVM did not allow balancing between modules and the alternative was to balance higher modules down using additional dissipative methods or running the high module active circuit to cause dissipation."  How can this problem be eliminated and not use an isolated 12V pack, on a 600V power pack?  In other words, I am trying to design a 600V battery pack that keeps every cell at the same voltage, uses active balancing and does not require a secondary, external power source.  Any suggestions?

2. We would like to modify the EV1402EVM so it does energy transfer from a cell to the module (battery pack), or from the module (battery pack) to a cell, similar to what the EM1401EVM used to do instead of from cell to isolated 12V pack.  How can this be done?  Do you have any application notes we can use to get started?

3. Is it still possible to purchase an EM1401EVM?  Any plans on updating the EM1402EVM to do cell to/from pack active balancing and eliminating the isolated 12V?

4. Any application notes on how to do active balancing with the bq79616-Q1?

Thank you for your support.

  • Hi,

    Addressing your questions:

    1. To balance each module, you have to design a separated matrix between each module. The topology is that you treat each module as a 'cell', but the 'cell' voltage is just a module voltage which is pretty high, you have to use and control so high voltage FETs for each module. This is possible but very difficult and high cost.

    2. You will need to modify the isolated DCDC from 12V  to Vstack, no application notes.

    3. No more resources than the ones on the website you have seen.

    4. Same as above 3. The active balancing topology is same no matter which AFE you are using.  

    Hope this helps.

  • Thank you Wayne.  This has been helpful.  Follow up question.

    In another support ticket, Taylor Vogt recommended to use a 12V battery for the 12V isolation source because this was how TI's testing was done.  Does it matter what the chemistry of the battery is?  Can it/should it be Li-Ion or Lead acid or something else?  Can you give me details on the battery TI used for it's testing?

  • Hi Ray,

    The output 12V has two parameters only, those are voltage and current, it doesn't care the chemistry of the battery. The tested battery should be lead acid but I believe it works for Li-Ion also.  

  • Hello Wayne,

    I have purchased a 12V lead acid battery and I am using that for my isolated 12V.  I have the EMB1402 all hooked up and it is operational but not working as expected.  This is what I have:

    For internal reasons)I had to use a non TI micro controller.  I had to rewrite the UART routines but now everything seems to be up and running.  I have a battery pack simulator with 14 resistors and one battery.  All cells with resistors measure about 3.2V.  The cell with the battery is measuring about 3.6V.  I am testing the EM1402 testing software written by Stephen Holland in its default mode of BalanceToAverage.  With this arrangement I am forcing the software to discharge BAT15 down to the average voltage of about 3.2V.  In testing the software I can see the program trying to discharge the highest cell voltage, in this case it is my Battery 15 to bring the battery voltage down to the average voltage.  The problem is battery15's voltage is only going up.  It is not going down even though the software is telling it to discharge.  As a test, I've forced the software (in the EMB_Start_Command() function) to charge the battery thinking something is backwards.  No change, battery 15 still is increasing. 

    1. Is this normal operation or is something wrong?

    2. The lead acid battery is at about 12.5V.  Battery 15 is at 3.6V.  It is my understanding that even though the lead acid battery is at a higher potential then the Cell battery, energy/current can still flow from the cell voltage (a lower voltage) to the lead acid battery (a higher voltage) so it can be used at a later time.  Is this correct?

    3. If #2 is correct, can you give me some trouble shooting tips to figure out what the problem is?  If #2 is incorrect, can you please explain what I am missing?  I am stumped on this problem.  I am pretty confident of the software.  I could use some hardware troubleshooting tips here.

    4. Could the fact that I am using 14 resistors instead of batteries be causing issues?

    5. It is my understand that current can only flow from cell to isolated 12V OR from isolated 12V to cell?  Never from cell to cell.  Is this correct?

  • Ray,

    It should be software configuration issue. Please check pin 9, DIR, of EMB1499 to confirm it.

    Answers for your questions: 1. Wrong, 2. Correct. 4. Resistors are not the issue. 5. Correct. 

  • Hello Wayne,

    I am still having problems with the EMB1428.  I found a tech support from Leslie Marquez written over 3 years ago that gives a good explanation of the signals between EMB1428 and EMB1499.  I have a few follow up questions to his email.  Here is his email.

    "These are the signals between EMB1428 and EMB1499. I explain below what they do. These devices are meant to be used together since the EMB1428 device is expecting these signals from EMB1499.

    In summary:

    • EN pin is an output from EMB1428 to indicate to EMB1499 device when to start or stop balancing (start with EN is high and stop when EN is low).
    • DIR pin is an output from EMB1428 too, and it indicates to EMB1499 whether to charge or discharge the selected cell when balancing.
    • DIR_RT is an output from EMB1499 going into EMB1428 and it should be the complement of DIR signal (see timing for this in the datasheet).
    • DONE is an output from EMB1499 to indicate to EMB1428 when the charge/discharge cycle is done (high when the current charge/discharge cycle is done, and low when it is in progress).
    • FAULT[2-0] is an output from EMB1499 to indicate to EMB1428 that a fault occurred. See "Fault Detection and Fault Codes" on page 13 of the EMB1499 datasheet for description of each fault code."

    I can't even get the first step done.

    With reference to the EM1402 schematic, TIDA-00817 and this picture (sorry for the poor quality of the logic traces):

    1. I am not seeing the EN signal from U18 (EMB1428, TOP Stack, page 6) go high.  It seems stuck low.  How do you get the EN signal from the EMB1428 to go high? 

    2. I am sending the command to discharge cell 15.  The SPI signals are correct.  What logic should the DIR pin be for discharge?  How soon after MOSI is complete will DIR be valid?  I can not find any timing information for the DIR signal.  The feed back I am getting on SDI (not shown in trace) is 0xe0 which I think is correct.

    CS to U18 is working properly.  It goes low earlier in this trace and goes high later. 

  • Ray,

    cmd[3]=1 is for discharge, 0 is for charge. Please refer to page 45 of the below document for details. Setting one certain channel connected means EN high. 

    https://www.ti.com/lit/ug/sluuas6a/sluuas6a.pdf?ts=1672765081601&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FEMB1428Q%253FkeyMatch%253DEMB1428Q%2526tisearch%253Dsearch-everything%2526usecase%253DGPN

    Please also refer to the EVM sample code as below. 

    www.ti.com/.../snvc188