Van Alternators

how long does it take to charge a van battery when it is idling (using the alternator)?
Is there a certain time that it takes approximately for a vehicles battery to charge while idling?
it will never reach a full charge just by running because the vehicle is using its power as the alternator charges the battery,it will only reach a little over half way of what it should have back in it,it will get enough to restart it in some cases but it wont reach a full charge,good luck.
HV 48v Alternator HHO GEET Vapor Carburetor Gasoline Vapor System