Yes it is clear your design is for high power, I was just trying to show on the example that CC is generated by the charger circuit, not by the the BMS.
HighHopes wrote:i still think the main DC/DC converter (PSFB in my case) has to set the CV and CC needed by the batteries and the BMS just manages when to shut off charge, what happens after charger is disconnected (like balancing) and monitoring battery health while in use.
Yes, it is exactly how the usual charger-BMS combos work.
where does it say that the BMS is involved with the charge profile?
Nowhere, it was just my idea, sorry.
Normally the balancing works with a hysteresis voltage control by the BMS: when a cell from the string reaches the top voltage (e.g. 4.2V), then the uC on the BMS cuts off the charger current with a MOSFET (in series with the whole pack) and enables the bleed resistor connected parallel with that cell. Then waits until the cell voltage falls to 4.1V (or similar) and then enables the charge current again for a short time, until the cell is 4.2V again. During that short ON period the charge of the other cells is also increased a little bit.
But from my experience there is a potential problem if the charge current is very high: there is some latency from a BMS module (an IC with 4..8 cells) detecting a cell at 4.2V to the uC cutting off the charge current, because shifting the information through the BMS modules and processing by the uC takes some time. If the charge current is high and the pack is already being balanced for some time (some cells are very much at the top), then due to the latency the cells at the top voltage can get to a higher voltage (e.g. 4.3V) very quickly, that is out of spec. To avoid this, it would be useful to reduce the charge current in the balancing phase, because then the raising of the cell voltages is slower.
On your block diagram there is a CAN/SPI comm. between the BMS and the charger and I thought you also intend it to control the charger current.