Wind turbines, solar panels and most charging devices including small engine driven generators have limited current producing capability. Batteries can be charged at reasonably high currents unless fully charged so you can safely connect a turbine or a solar panel to a modest size battery and as the source has restricted current capability the source voltage will be dragged down to that of the battery and all is well.

Solar panels have an inherent current limit based on the size and light level and you can short them and they just produce constant current.

A wind turbine can't supply more current than the wind speed and prop diameter allows so once again even if you short its output there will be only a limited current. If this limited current is within the capability of the battery to handle then you just connect the thing to the battery and let it get on with it.

For very tiny batteries you would exceed their safe charging current if you connect them to large panels or turbines but normally batteries sized for the system can just take it.

If the charging source is capable of very high short circuit currents ( monster engine driven generators or other batteries) then you need to add resistance to the circuit to limit the current.

For dealing with batteries and powerful generators you can use Ohm's law and the current will be the difference in voltage divided by the circuit resistance.

Doesn't work for solar as the panels are current sources. Works a bit for wind but again the resistance is not the only factor determining the current so it will always be less than the prediction from Ohm's law.