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BQ20Z95: Two bq20z95 in series

user 1234
Prodigy 185 points

Part Number: BQ20Z95

I have to make a 6S BMS for Li-ion.
Can i connect in series two 3S packs using bq20z95 on each 3S pack.


On SMBus only current has to be read via lowest bq20z95.

1. While discharge, i think this system will work ok, as if either one is off, there will be no voltage output.

2. Whle on charging, problem will arise, if lower one is off, and charger is connected, system will never get turn on.
Is there any solution to it?

3. any other downside?

4. is there any other 6S complete solution like bq20z95, which has all features of bq20z95

  • 0
    TI__Guru* 76230 points
    Hi
    For 6s, i would recommend using the bq34z100 or bq34110 and a separate protector. While stringing two of the devices in series has been done before by some customers, it isn't recommended as there are a bunch of hurdles you would have to jump through to get it to work. The comm lines will have to be isolated and you will have to use an i2c multiplexer for the device since they have the same smbus addresses.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 185 points

    Hi Onyx,

    Comm from upper device is not needed. As I said, only current flowing info is required on SMbus nothing else.
    Can you tell me what could be other hurdles in this?
    One obvious is as I mentioned in post#1, any way to solve this?

  • 0 in reply to user 1234
    TI__Guru* 76230 points
    Hi
    The chips weren't designed to be operated this way and this is not something we have tested before so we can't envisage all the hurdles you will face. You will need to run multiple tests to verify the functionality. Let me know how this turns out for you if you decide to go with this approach.

    thanks
    Onyx