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BQ76930: Battery pack monitoring

user4408068
Prodigy 165 points
Part Number: BQ76930
Other Parts Discussed in Thread: BQ34110, BQ34Z100-G1, BQ76940, BQ78350-R1, BQ76920, BQ40Z50-R1

Hi TI team,

I am Ameesh from Trenser technologies. 
For our new Industrial Base Station Monitoring device we are planning to use bq76930 for Battery pack monitoring.
Our battery Li-ion battery pack contains multiple 12V batteries. We gone through the datasheet of bq76930, from that understood each cell monitoring maximum voltage 4V. My question is our battery pack have three 12V batteries. Is it possible to monitor this battery pack completely and individual cells? If yes how? could you please help? Looking for your early reply. 
Thanks & Regards, 
Ameesh
  • 0
    TI__Guru* 81034 points

    Hi Ameesh,

    For the BQ76930, you need to connect each of the individual batter cells for everything to work properly. Otherwise you would not be able to protect against over-voltage and under-voltage on each cell and the ADC for monitoring cannot measure beyond 6V. If you can connect to the cells individually, the BQ76930 is a great fit for your application.

    If your goal is only to monitor the Pack state-of-charge (without individual cell protection and cell voltage measurements), then a pack battery gauge like the BQ34Z100-G1 or the BQ34110 might be a better fit. These devices can monitor Pack voltage, battery current, and temperature to accurately gauge the remaining capacity of the battery pack. 

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 165 points

    Dear Matt,

    Thanks for your support.

    My requirement is need to monitor individual battery complete status ( cell voltage and current measurement and state-of-charge). If possible need to monitor the Pack status too.

    In the case of BQ76930 is best suit for 3.6v-4.2V battery packs. But we need to monitor 12V batteries. In all industrial locations 3 or 4 strings of 12V batteries.

    We need to monitor this 12V battery string's (pack)  complete status ( cell voltage and current measurement and state-of-charge). If possible need to monitor the total Pack status too.

    So could you please suggest a solution for that. 

    Once again thanks for your valuable comments. Looking forward to hear from you.

    Thanks and Regards,

    Ameesh

  • 0 in reply to user4408068
    TI__Guru* 81034 points

    Hi Ameesh,

    I am not completely sure I understand.

    Your system will have up to 4 strings of 12V each (total of 12 cells). Is this correct? In this case BQ76940 (up to 15 cells) is suitable. This will monitor and protect all of the individual cells, measure the current and temperature also. If you use the BQ78350-R1 with the BQ76940, it will report state-of-charge, remaining capacity, and will monitor the total pack voltage (48V). 

    If you need to monitor each 12V Pack voltage individually, this can be done with a simple microcontroller. It can read the cell voltages from the BQ78350-R1 and compute the voltage of each 12V Pack. 

    Am I understanding correctly that the 4 12V Packs are connected in serial? Or are the separate batteries that need to be monitored individually? In this case, you would need one BQ76920 for each Pack.

    Regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 165 points

    Dear Matt,

    Yep, Our system have  up to 4 strings of 12V each (total of 12 cells).

    BQ76940 is okay for us. But my question is shall we connect the 12V batteries directly to the chip. If my understanding right, the chip will handle max 4.2V in  a single channel(15*4.2V). If i am wrong please correct.

    4 12V Packs are connected in serial, but we need to monitor  individually and total voltage(single cell voltage,current and  state-of-charge like wise total string voltage,current and  state-of-charge).

    Could you please suggest a solution? Also any refence circuits or development boards are available?

    Thanks & Regards,

    Ameesh

  • 0 in reply to user4408068
    TI__Guru* 81034 points

    Ameesh,

    The individual cells (4.2V) need to all be connected directly to the BQ76940. The same current will flow through all of the cells in serial, so there is only one current measurement. 

    The simplest solutions is to use BQ76940 + BQ78350-R1 (battery gauge). The BQ78350-R1 reads all of the individual cell voltages, the current, and the temperature, and reports state-of-charge for the system (based on all 12 cells). A microcontroller can communicate with the BQ78350-R1 to read all of this information and make additional calculations if needed.

    If you really need separate state-of-charge reporting for each string, you can also add a BQ34Z100-G1 (battery gauge) per pack, but this increases the complexity. 

    One other option is to place one BQ40Z50-R1 device inside each pack. This is a fully featured battery gauge with advanced protection features. It needs to connect to the individual cells within the pack.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 165 points

    Dear Matt,

    These things are okay for me. But my question is i am getting 12V output from battery, no individual connection(No 4.2V).

    So i need to monitor 12V cells (need to monitor 12V 12 cells) . For that what will do?

     

    Thanks & Regards,

    Ameesh

  • 0 in reply to user4408068
    TI__Guru* 81034 points

    Hi Ameesh,

    So you are only able to monitor the pack voltages - this is much different from monitoring the cell voltages. Without access to the individual cells, you cannot do cell over-voltage and under-voltage protection on the cells. The packs may already include over-voltage protection per cell - you may want to check this. A 12V battery is made up of a number of individual cells, and simple over-voltage protection is often included.

    For gauging, you can use the BQ34Z100-G1. This device does not require individual cell connections. You can use one for the entire system, or one per 12V pack if you need to monitor state-of-charge individually per pack.

    For additional questions on the BQ34Z100-G1, I recommend starting a new E2E thread. This will ensure the correct expert on this device is notified and will be able to help give guidance.

    Best regards,

    Matt