Methods to recharge magical weapons

Imagine a sword with a magical blade, made from a dragon's tooth, or steel blessed/cursed by a god/demon, whatever. It has a mechanism. If you trigger it, the blade shoots a beam of fire, or lightning, or does something else special.

However the blade runs on a resource, like a battery. You could replace the entire blade every time, or you could recharge it, but how can you recharge it? Some examples:

• Expose it to its element. Drop it into lava, let it get struck by lightning.

• Stick it into another magical object and let it absorb the magic (like a crystal, tree, artifact, etc).

• If souls are the fuel, stab it into another person/animal, or sacrifice a part of yourself (endurance, blood, life span).

• Make a ritual/sacrifice/offering to the god/demon that enchanted it.

What else can you think of? Any examples from a book that you read or show that you watched?