[chbot] BMS - How they work?

[Marshland Engineering]

Aliexpress has many 2 3 and 4 cell BMS boards. 

I'm struggling to find out what exactly do they do ? 

See here https://www.aliexpress.com/item/33031988423.html

>From what I have read, Li-ion batteries have a very specific charging method.
I cant see this board doing anything like this.

I have a 12 Li-ion motorcycle battery with a very similar board in the
housing.  It uses 4 cells. Does it only charge each cell to 3.6 volts or so
and not 4.2 ? 

>From what I think, car and bike batteries use direct connections to the cells
for the high starting currents required but should have a completely separate
charging system. This can easily be done as the alternators can be isolated
from ground therefore providing a independent charging circuit that can
monitor each cell.    

Something like this. 

https://www.aliexpress.com/item/32800729065.html


Any thoughts?