How long do these batteries last in a Rustler XL-5. My Rustler which is less then a month old will go 12mins average on the 3000MAH that came with it. So I bought the 5000MAH one from Traxxas hopping to get more run time out of it. But so far with 2 runs on the 5 Series battery I have only gotten just about 15 mins each run. Is this normal or do I possibly have a bad battery pack. For charging I use the Traxxas EZ Peak quick charger #2930 and I keep a good eye on it to make sure it gets charged according to the charging and make sure that I dont leave it on there to long after.