While writing up artifacts and runes, I decided I needed to come up with a more precise version of a magical battery since I have a number of stories about recharging Farimon Chambers such as The New Girl.
This, of course, made me realize I made some mistakes earlier with resonance and feedback because I couldn't have diamonds be best for both an energy storage and act as a battery.
It also helps explain why writing a rune on a paper works as a one-shot spell but engraving it on a crystal block makes a rechargable magical source.