You realize amperage is dependent on the voltage too right? Kind of like pressure and fluid velocity. The higher the voltage difference the greater the current will flow. V=IR in a DC system. In the case of a battery, it is the difference between battery and alternator voltage that determines current flow to the battery.
Don't forget about the conductor size limiting current (amperage, not volts) flow, same thing on liquid delivery, lbs. of pressure and gallons or ounces per minute
As far as the battery storing energy and what is charging it is another subject altogether
Don't we love cars and how they work
