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Active cell balancing for LI-SOCL2 batteries

Abhijeet Kulkarni
Prodigy 10 points
Other Parts Discussed in Thread: TPS61031, BQ79616, TPS61030, TPS61023

Hello There,

I have designed an IOT sensor and it uses LI-SOCL2 batteries. I am using 3 batteries in parallel. I am using Schottky diode in series with each battery to prevent battery short circuit. In short it is three parallel units of "battery + schottky diode". My prototype works well and I would like to make an actual PCBA now.

I would like to get an answer for below queries:

1. Is there any active balancing solution for LI-SOCL2 batteries?

2. I am using E70-915T30S for my RF + MCU. Which supercapacitor is recommended to provide a peak power of 30dBm? I can use a supercapacitor (3.3V) and then boost it to 5V using TPS61031. At the moment I am using external 3.3V /100mA (this is set in my programmable power supply) as input to TPS61031.

Kindly suggest me pointers.

Thanks

Abhijeet

  • 0
    TI__Genius 17370 points

    Hi Abhijeet,

    The only active CB solution we offer is the older https://www.ti.com/tool/TIDA-00817 design but we are more focused on passive CB solutions like the bq79606 and bq79616 devices. I will forward you over to the TPS support team to answer the other.

    Regards,

    Taylor

  • 0
    Prodigy 10 points

    Hi Taylor,

    Thanks a lot for your answer. Passive CB is also okay.

    Do you have any reference schematic that I can try for passive CB? Either of bq79606 or bq79616 should be okay. I am looking more towards cell balancing to maximize battery life and product working life.

    Thanks

    Abhijeet

  • 0
    TI__Mastermind 34231 points

    Hi Abhijeet,

    May I know the supercapacitor voltage range? 

  • 0 in reply to Zack Liu
    Prodigy 10 points

    Hi Zack,

    I am planning to set TPS61030 output to 5V. Hence the supercap voltage range should be higher than that. I can connect two supercaps in series so that voltage rating of individual supercap can be smaller.

    My Circuit demands 375mA average current for 650ms and 14mA constant current for 1.1s. This means, I have 1.1s to charge my supercaps. During the 650ms time, my peak current can go upto 600mA. The output voltage is always 5V.

    If you have any recommendation regarding above requirements, I will certainly try them out. 

    By the way, these are the worst case requirements and I am designing based on these worst parameters. 

    Thanks

    Abhijeet

  • 0 in reply to Abhijeet Kulkarni
    TI__Mastermind 34231 points

    Hi Abhijeet,

    For your application, TPS61023 is recommended. TPS61023 is a 5V voltage rating boost device, which has 3.7A typ switch valley current limit. It should be enough to output 5V/ 600mA  peak power.

  • 0 in reply to Zack Liu
    Prodigy 10 points

    Hi Zack,

    How about supercaps? Any recommendations? My plan was 61030 boost and supercaps at the output of the chip. So any additional current can be supplied by the supercaps. This will help me if the battery voltage starts going below 2.7V.

    Thanks

    Abhijeet

  • 0 in reply to Abhijeet Kulkarni
    TI__Mastermind 34231 points

    Hello Abhijeet,

    Sorry I'm little bit confused. 

    In your first question, you said:

    I can use a supercapacitor (3.3V) and then boost it to 5V using TPS61031.

    In my understanding, the supercap is the boost circuit input, right? You could share the system block diagram.

  • 0 in reply to Zack Liu
    Prodigy 10 points

    Hi Zack,

    I am evaluating two options here:

    1. Battery - buck-boost (output 3.3V) - Super caps - Boost (5V) - RF module

    2. Battery - Boost (5V) - supercaps - RF Module

    In option 1 above, supercaps will be at the input of TPS61030 and in option 2, supercaps will be at the output of TPS61030. In either case, I will use TPS61030 to boost the input. 

    Hence, I am looking for supercaps that will suit both above options. Additionally, I am planning to use two supercaps in series so that voltage rating of individual supercap can be 3V or similar.

    I hope, this clears the confusion.

    Thanks

    Abhijeet

  • 0 in reply to Abhijeet Kulkarni
    TI__Mastermind 34231 points

    Hi Abhijeet,

    Thank you for clarifying the two options.

    I'm not familiar with supercap selection. You can take a look at AVX. They have lots of supercap products.