During the charge, the battery receives current. This processus must remains within set limits :

The voltage ;
The intensity;
The time ;
The temperature ;
The gas outlet.

To feel those needs, there is an adapted charger for each type of battery.

For example:
The on-board charger for light vehicle and 2-wheelers (220V - 15A single phase network supply);
The static charger for heavyload and industrial vehicules (380V - 20A and more, three phase supply).

Those chargers are driven by micro-processor. They adapt themselves to the needs of the batteries and remain within the accepted limits. The supply cut is done automatically at the end of the charge.