It takes a lot of energy to create a battery. The "old fashioned" way of doing it is cast a spell, then undo the spell without magic. For example, using magic to tie a knot and then untying the knot with your fingers. It releases a small amount of magical energy that can be collected.
But these are tiny amounts of energy that take time to collect, especially if it's just me working on it by myself. Apparently there was a professor back on my world that used his students to create batteries for a worse case scenario, but even with a classroom of students semester after semester, he made maybe four large batteries and a dozen or less small ones?
So, I can make a battery myself but it takes time. This would give a large battery in a much faster time frame and with how quickly things change here, that's probably a good idea.