BMS boards take care of all the charging requirements.
If only this was true. I've been searching around BMS boards and to be honest I haven't found a single review of one that actually works.
I know the single cells 1S BMS boards work fine, but it's when you move to 2S to 7S that things come apart. I've seen reviews of boards that just don't work period, boards which are sold as charging BMSs, but are just protection boards, boards which will not cut out to over 4.3v+ per cell, boards that let the voltage drop to 2v per cell and the better ones still appear to use a resistive drain on the high cells to drain them down to the low cells for balancing and can't keep up with a sensible charge rate.
I am still to find a multicell BMS which supports:
Proper cc/cv charge
Proper active cell balancing, or at least cross-cell balance charging.
Proper cut out voltages
Supports discharge AND charge
I can find a dozen Lithium chargers which support all of the above, but they don't typically like being in the circuit with the load and don't like being charge/discharge controllers, so they would need relay switching between charge and discharge. All of which makes them fairly useless with solar.
I watched lots of Adam Welsh's videos and Julian Lett videos and I don't think between them they have found a reliable multi-cell BMS. The best they seem to have come up with are Frankenstein devices with BMS to resistive balance the cells, a 12.6V cc/cv charge module to feed it and a boost converter to bump the 12V supply up. I'm not sure this could be connected to a solar charge controller, I'm pretty sure it couldn't as it would be trying to sense a battery not a charger board.
I don't even think they showed this set up under proper test, regards the BMS balancing cells or the proper cut off voltage of 12.6V (for 3S).
The Adam Welsh videos on Lithium solar charge controllers didn't seem to go well either. I don't think he found a reliable lithium charger which didn't float charge and ended up using a "Gell lead acid" mode and a 7 series pack to match the voltage of a 24V gell LA.