After looking for a couple days, I got my boy a used Traxxas Emaxx. Now, I need help understand batteries. The batteries that came with this thing only held a charge for about 5 minutes. Off to the hobby shop we go. Wow, these things aren't cheap.

What the difference between a 2400 and a 4500mah battery? Is it run time or release of power? It came with 7 cells but the hobby shop tells me I only need a 6 cell battery. At one point, this guy was talking abut these new lipo things that will have a long run time but I needed to change a bunch of things. Where do you guys buy your batteries. I like to support my local shop, but if they are ten bucks more then the net, I will order on line. They range from 20 bucks to 60. Oh, It has two brushed Titan motors that require two packs. That much I do know, if that helps. I am thinking about buying 4 packs. That must last for an hour?