Hi,
I have just started my Master's thesis on Li-ion Battery Management system, with the intention of using it in Hybrid Electric Vehicles. I am thinking of testing it using 4 LiFePo4 cells in series first and then stacking more such strings.
My aim is to implement passive cell balancing first (and active cell balancing later) during charging and discharging of 4 cells.
So, I have been researching on the chips provided by TI for BMS and am a bit confused about which ones to use. So, I have some options as follows:
1. BQ76PL536 - this is recommended for HEVs and is also stackable, which solves my purpose, but the only thing that it misses is that it does not use TI's impedance track technology. I think that impedance track technology is very efficient and hence, would like to use it with this chip if possible. I dont know if we can implement impedance track technology in this chip. Could you please let me know if it is possible?
2. BQ20z65-R1 - This chip provides fuel gauging using impedance track technology for 4 cells in series, but it does not have cell balancing option. I would like to use it because of its guel gauging efficiency, but I don't know if it can be used for cell balancing as it does not have the control register to control the FETs as it is there in BQ76PL536. Also, it is not mentioned in the datasheet whether it is stackable or not. could you please clear these two questions of mine regarding this chip?
3. BQ34z100 - This also uses the impedance track technology, but I dont think it gives the individual cell voltages and other cell characteristics. It gives the total battery pack characteristics. Is that right or can we also get individual cell data because I want to implement a passive cell balancing algorithm using all the characteristics of each cell and not only cell voltage. Also, it does not have the option for cell balancing.
Hence, I would like to know what would you suggest is the best option for me to implement cell balancing on 4 LiFePo4 cells in series (using the impedance track techology if possible) and having an option for stackability.
I am open to using Evaluation boards too, which would have the FETs and cell balancing circuit embedded into it.
Please let me know your suggestions. It would be of great help to me.
Thanks,
Parth
Graduate candidate,
School of ECE,
Georgia Tech
