First, you should be able to get more then three or 4 flights off your existing pack. buy a loaded volt meter as suggested earlier. Tower has one for $10 and the correct cables for your radio. Don't even think of charging a pack more then 700 ma with a 50 ma charger, it will never charge fully and you will crash. Use the volt meter on every flight untill you get an idea how much you can fly in reality before spending a bunch of money. Make sure you give a good overnight to your batteries before you go fly and never use a fast field charger if you can avoid it, your batteries will be happier. If you need to ,you can go to a 1000-1200 ma pack but remember your transmitter will run out of juice to. Make sure to charge whatever you end up with a 10% charge rate.