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BQ34Z100 and BQ77910 for Lithium Titanate Oxide cells

Valentin JOSSE
Prodigy 20 points
Other Parts Discussed in Thread: BQ34Z100, BQ34Z100-G1

Hi guys,

I have to design a go-kart battery pack with lithium titanate oxide cells. This battery pack must have BMS for estimating its SOC and its SOH. The BMS will have to have charging overvoltage protection, discharging undervoltage protection, thermamal protection and will have to ensure a correct cells balancing. The battery pack will not have a  battery charger inside it.

The batteys pack will be make with 4 strings that will be placed in parallel. Each string will have 22 LTO cells placed in series.

 

I would like to know wether or not I could use the BQ34Z100 for realising the battery gauge and the BQ77910 for ensuring the cell balancing and the cell protection.

 

Many thanks for you help

 

Valentin

 

 

  • 0
    TI__Guru 73830 points

    Valentin,

    The operating voltage range for LTO cells is too low for the bq77910 to balance them and we do not have a balancing device that will fit these cells. The bq34z100 should be able to gauge the cells and we have a couple of ChemIDs for LTO cells in the portfolio.

    Regards

    Tom

  • 0 in reply to ThomasCosby
    Prodigy 20 points

    Hi Tom,

    Indeed the BQ77910's minimum OVP threshold can't be lower than 2,8V, whereas the cut-off voltage of an LTO cell is 2,75V. So are you sure that you do not have any other components to suggest?

    Regrading the full gauge BQ34Z100, what do you mean by "ChemIDs" ? Would this IC be abble to estimate the SoC and SoH of my LTO battery pack?

    Many thanks,

    Valentin

  • 0 in reply to Valentin JOSSE
    TI__Guru 73830 points

    Valentin,

    Our high cell count AFE's / cell balancing devices do not support that discharge range. The ChemID is a file that contains and OCV table and series resistance table that represents the cell that you are using. The device uses this data to run simulations to estimate capacity. It also updates the series resistance table as the cells age to improve the gauging accuracy. If we do not have a ChemID for your cell, then we can characterize your cell and create one.

    Tom

  • 0 in reply to ThomasCosby
    Prodigy 70 points
    Tom, I would like to find out if T.I. offers an LTO solution. It sounds as if the BQ34Z100 can charge and characterize LTO cells, it just can't balance the cells; is that correct? _ David Quinn
  • 0 in reply to David Quinn
    TI__Guru 73830 points

    David, 

    The bq34z100-G1 should be able to gauge the Lithium Titanate cells, but we do not have protectors or cell balancing devices for these cells. There is not much activity on these cells, so the investment is limited.

    Tom