within the first 2 weeks after i changed my pullies, and added an electric fan my battery died 3 times because of my electric fan. The stock POS alternator only puts out so much charge at idle as it is and by slowing it down with pullies you are reducing the output of the alternator, you wont fry it,"the faster it turns the more it can put out up to its max". I eventually went back to stock pullies and went with a 140 amp 1 wire alternator from powermaster. $160. The stock alternator only puts out 70 amps at max rpm, now think about at idle and slowing it down even more. 20-30? You could always use the stock alt pulley to help with the output and you dont have an electric fan anyway so you might be alright.