Battery options

yeah I forgot about the zippies. I have heard they have good bang for your buck. This is just a smaller project. No high speed or voltage. I am using a mamba maxx that I had on hand, I don't have a motor yet because I havnt decided but I am not going too spend a lot so something like a feagio or maybe a medusa. Another thing is how the heck am I gunna get a batt in there I would love 4s but doubt that I could get a 3 cell in there. Once this is done I need a new project.....