OK, so the resolution of CVL is 10mV: for a battery impedance of typ 10 - 20mOhm, this results in a charge current change of 0.5 - 1A. So if the BMS has a balancing current of <0.5A, then it IS going to oscillate. Nothing you can do about that. Long damping will result in a slow adjustment - possibly with overshoot.
for 50mA balancing current (25mA effective as most balancers are restricted to a 50% duty cycle) and 10 mOhm battery impedance, then the CVL needs to be improved in resolution to 250uV steps (40 times improvement). The Multiplus design would need a total control makeover to achieve this. This is why I don’t like control by CVL. However, with the requirement for solar export, this is unavoidable.
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If algorithm is based on max single cell voltage, rather than battery total voltage, the performance will be better. (Making an excuse for CVL if the cell delta voltage is high is not the best approach - to my knowledge all BMS report max and min cell voltages if not all of the voltages.)
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If PID with appropriate constants are used, Kp,Ki and Kd, then one can get optimum performance. However, all of these need tweaking depending on battery impedance.
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If balancing currents are higher than 0.5A (/ 100Ah, ) then performance will be much better.
The BMS board that Pylontech and many others use was designed for Data Center UPS balancing, not Solar balancing: the market is much larger. As such, balancing time is not restricted to solar hours.
Apologies to @hans66 for hijacking his topic.
