Other Parts Discussed in Thread: BQ76940
I am trying to design a system for charging a Battery Pack.
The batttery pack consists of ~75 cells of AgZnO chemistry cells, whose voltage is 2.1V when FULL and 0V when EMPTY.
The battery pack shall be charged with CONSTANT CURRENT using a dedicated battery charger with either 10A or 5A according to the avarage cell voltages. The battery charge current is controlled using RS232. The Battery charger is only activated when charging is required.
I am considering using TI battery monitors BQ76PL455A, BQ76940.
For the control of battery charging I shall use MSP432 with ETHERNET control interface.
The control interface shall ALWAYS be ON.
I need to know ONLY the voltage of each cell.
The battery pack shall be replacable and I want to be able to measure even when the cells are EMPTY (0 Volts).
I am confused about the power supply input of these BMS ICs. The 'TOP' pin is shown in the datasheets, should be conntected the most positive voltage in each battery pack within the BMS.
My interpretation of this is that, when the cells are totally EMPTY and the charger is not activated, not POWERED, I can not measure the cell voltages because the TOP pin voltage is 0V.
I want to be able to measure the cell voltages while charging and while not charging when the charger is OFF.
Is there a way to power the stacked BMS with an external supply?
In section 6.3 it is stated Vtop could be between 12V and 79.2V. But Vsense16 = TOP. To my understanding means that supply of the BMS is again the battery pack. Again if the batteries are EMPTY or there are NO INSTALLED batteries I can not see 0V or that there are no batteries.
I am attaching a block diagram of the system I am considering.
I would be glad if you could help me.
Kind Regards
