I'm looking to get a few new batteries for my Traxxax EZ-Start wand. The book says I can use NIMH or NICDS just as long as they are 7.2 volts. What is the differance between the two? I have a .26max on one of my Revos and some times its a little hard to start. The batteries always need to be fully charged to spin it fast enough and they die quickly. I wanted to get some thing with alot of power. Can someone please explain the difference between the two types of batteries. Thank You. (I did do a serch)