The battery in my ez started went out, I see on the battery that is in it now is 1500mah but the only one I can find in stores is 1800mah. Can I get the 1800mah battery and it work in the ez starter?
Yes. Voltage and Current are what you need to be careful about, as this is, in terms of the water analogy, the water pressure, and speed of the water. So if you increase this you may damage something, however the Mah is just like a fuel tank- the higher, the longer it lasts.
If it's a Traxxas unit, 100% positive it will work fine. In fact, the battery will last slightly longer. I use both 1500 and 1800... All 6 cell 7.2v , just to be clear.