Low voltage *usually* means that your alternator is about to kick. Check all your conections to make sure nothing came lose. Sometimes the alternator takes the battery with it so don't be surprised if both are bad. Another thing to check would be the condition of your belt and the belt tensioner. If the belt is slipping or broken you won't be getting any charge from the alternator. Its really really easy to replace the alternator, I'm sure you could get one from a salvage yard if you didn't want to buy a new or rebuilt one.