How the voltage based active cell balancing model works for larger voltage difference and not working for smaller voltage difference ?

If we keep cell 1 voltage as 3.2 and cell 2 voltage 3.7 then both cells gets balanced at 3.45 V but if we keep cell 1 voltage 3.5 V and cell 2 voltage as 3.7 then both cells should balanced at 3.6 V but they do not get balnced at 3.6 V

Answer 1

[Joel Van Sickel]

You are modelling lithium ion batteries and giving them different nominal voltages. These batteries are not linear and would not necessarily balance to an average of the two voltages. That would only be expected with capacitors of the exact same capacitance. In your case, because the batteries have different nominal voltages, even though they have the same AH rating, that does not mean they have the same energy storage capacity, because it is AH at the rated voltage. Even if the batteries did have the exact same ratings, you cannot expect a linear relationship between voltage. What you can expect is a linear relationship between 2 identical batteries between state of charge. an 80% battery balancing with a 40% battery will balance to somewhat less than 60% (due to losses), but that does not mean the voltages will change linearly because batteries don't have a linear relaitonship between Soc And output voltage.