Hi,
I'm currently designing a smart battery management system for a 32Ah battery pack containing 3 lithium ion cells connected in series. The BQ20Z655-R1 IC meets most of the design requirements, but the internal cell balancing currents will not be sufficient to balance the cells within the charging time. Does the BQ20Z655-R1 in any way support external cell balancing? Would a setup like the one shown in “SLUA420A - Fast Cell Balancing Using External MOSFET” work? From what I understand, there is no way to configure the BQ20Z655-R1 to balance only one cell at a time (rotation balancing) so adjacent cells could attempt to balance simultaneously using the suggested setup. The document mentions that:
“In practice, it (simultaneous balancing of adjacent cells) is not an issue because the amount of time required for balancing each cell is evaluated on a per charging-cycle basis by the Impedance Track™ algorithm”
Does the BQ20Z655-R1 do this as well? If two adjacent cells need balancing and if the balancing time for each cell is only calculated once per cycle at the start of charging, wouldn't that result in only one of the two cells ever becoming properly balanced in a single cycle?
Any information would be greatly appreciated.
Best Regards,
Daniel