BQ76952: Testing

Hi Nitin,

Cell balancing will not work properly with a resistive cell simulator.  When the part turns on balancing on a cell (the higher voltage cell induced by the trimpot) it will affect all the other voltages. The voltage change may be seen as a fault and terminate the balancing in a few ms.  If it runs another cell may be measured as the high voltage and be selected for the next balance interval.  Use a separate source connected across the cell to simulate a high voltage for balancing.   For example if you have one supply (source) connected across V16 to V0 and the divider, then connect a second supply (source) set at a higher voltage per cell than the average across one single cell.  The second supply will provide a steady voltage and the current for the balance circuit.  The Vn and Vn-1 voltages should remain relatively stable while the VCn and VCn-1 move to allow the external balancing circuit to operate.  You should be able to see the balance current on the supply display.

Testing SCD with a supply can be difficult.  Cells will pull down based on the cell resistance, system interconnect resistance (including FETs) and the shorting resistance.  They will deliver as much current as they can.  When the discharge FET turns off or the short comes loose (chatter) the cells will have an inductive response.   A supply will have a regulation loop which will look different from a battery.  Some supplies will have a large output capacitance which will provide a large current surge to trip the SCD.  Current, voltage, and power loops if present may give unexpected to undesired results, or may work just fine. A supply which could provide 80A at 60V would be 4800W, likely very expensive, and may not like a battery.  A well behaved supply which could provide a few hundred watts at high current/low voltage might better simulate a battery.  Check your supply manual or with the manufacturer for recommendations.