@Cal, over the next few days I will create a proper itemized cost for the 4x cell board. However, I am still hoping to hear other's opinions on what V measurement accuracy is required for this application. I totally get that 12 bits is better than 8, but 16 is better too. Where is the cut off for useless additional accuracy?
The ADC1115 will not tolerate a V differential higher than 5V, right? So your design is using resistors to divide the voltage of cells 1, 2, and 3 down to within 5V of cell 0, right? So those resistors introduce new variables with respect to measuring cell V differences, right?
Also, maybe I missed it, but did you confirm that you must assign different addresses to the 4x cell boards in order to make a BMS handle more than a 12V pack? And did you understand a nice solution to that would be to use 1 attiny per 4x cell board so it can do the serial communication with the controller?
In other words, is our best current idea for a higher precision solution with the all-boards-identical requirement as follows:
1 attiny getting it's V off of cell 0.
2 ADC1115. 1 will be used to measure the V of the 4 cells. Where cells 1, 2, and 3 have resistors to divide their V down to a tolerable value for the ADC. 1 ADC will be used to measure thermistors on each cell (again, not terribly important).
The ADC1115 will not tolerate a V differential higher than 5V, right? So your design is using resistors to divide the voltage of cells 1, 2, and 3 down to within 5V of cell 0, right? So those resistors introduce new variables with respect to measuring cell V differences, right?
Also, maybe I missed it, but did you confirm that you must assign different addresses to the 4x cell boards in order to make a BMS handle more than a 12V pack? And did you understand a nice solution to that would be to use 1 attiny per 4x cell board so it can do the serial communication with the controller?
In other words, is our best current idea for a higher precision solution with the all-boards-identical requirement as follows:
1 attiny getting it's V off of cell 0.
2 ADC1115. 1 will be used to measure the V of the 4 cells. Where cells 1, 2, and 3 have resistors to divide their V down to a tolerable value for the ADC. 1 ADC will be used to measure thermistors on each cell (again, not terribly important).