For a BMS with 15 cells, I have made connection as in Fig A of attached hand-drawn image. I am using host controlled balancing and am sending balancing command every 2 sec. I am reading 14th cell voltage from C15. To balance 15th cell, I am setting last bit and for 14th cell, I am setting 2nd last bit of the balancing register. The third last bit is always 0. However, I am getting voltage reading error in this configuration whenever balancing is on.
If I modify the schematic to as shown in figure B, things work fine. I am reading cell 15 voltage from C16, 14 from C14 and balancing 14th cell with third last bit. I do not get any voltage reading error in this case.
Referring to the datasheet, Fig A is the way to do the connection. What am I doing wrong here? And why is Fig B working?
Also, Fig C is should be equivalent to Fig A. In Fig C, I have shorted unused pin to higher pin while in Fig A, I have shorted it to lower pin. Any of the two methods should be correct as per the datasheet. However, even in Fig C I am getting voltage reading error.
I this not only for 15S, it extends till 3S. I connect N to C16 and then short 15 till N-1 and connect this shorted line to cell N-1 through balancing resistor (as shown in schematic). This does not work and keep getting errors in cell voltage when balancing is on. However, connecting cell N-1 through a resistor to both C15 and C(N-1) works.
I am using the AFE only for cell voltage reading and host controlled balancing. No other function is used.
Values of R is 47 Ohm and C is 1uF.
Kindly help me with this issue.
