What determines the charge of an electron? So I am thinking of making a machine that turns electrons into positrons.
So you put as many electrons as you want in one side and positrons come out the other side. This will solve all out energy problems!
But before I start my project I need to know what determines the change of an electron.
Right now, the only way to make antimatter is particle accelerators but these are super uneconomical and inefficient so I want to make a machine that is economical and efficient but I don't know how... if my machine is physically impossible to make, theoretically, what machine will allow me to do this? Will it ever be invented or is it just too impossible to make?
 A: The charge of an electron is part of the definition of an electron. If you have a particle with a different charge than $-e$ then it is not an electron by definition. There is currently no deeper theory of why there should exist particles with the basic defining properties of an electron (charge $-e$, mass ~511 keV, spin 1/2, ...). These properties just go into the theory as a basic ingredient.
If you ask the question "is there any process which changes the net charge" then the answer is no. There are very strong theoretical reasons for believing that charge is exactly conserved in all reactions in nature. As far as direct experimental evidence goes, the Particle Data Group lists the limit on the rate of charge changing interactions as less than once per $6.4\times10^{24}\ \mathrm{yr}$ (possibly not available on the pdg website, but available here - thanks Ali. It is also available in the print version of the review.).
Particle accelerators do not produce antimatter by converting charged particles into their antiparticles like $e^- \to e^+$, rather they work by pair production processes where the net charge is conserved, for example $e^- \to e^- + e^- + e^+$.
