In Mutants and Masterminds, one of the flaws a power can have is called "Limited Uses", which decreases the number of times a power can be used from infinite to some finite number. It's used most often with devises to represent ammo or fuel.
My question: How would I go about creating a battery device? That is, say I make a weapon with the limited use flaw but I want to give the character a couple of "batteries" that he can spend an action to put into the weapon and recharge it. Essentially, how would I make ammo clips?
Would they be another, separate device? What would they cost (in power points)?
This would strike me as a modification to the 'Limited Use' complication. It all depends on how frequently you have to do it and how long it takes in combat.
Is reloading a free action? That's not a 'Limited Use', it's a description. If you can run out of reloads, that's the 'limited' part of limited use, and I don't know how you'd reload your spare clips. Perhaps you could use a Hero Point to change the scene: "I'd like to spend a Hero Point. When Gobsmacker hit my teammate Glory into that pile of crates, maybe one of the ones that smashed open had a bunch of magazines?"
Is reloading a move-equivalent action? If you can reload and shoot in the same turn, it's not such a huge limitation. Maybe you can weaken the cost reduction of the flaw to -1point/2 ranks?
Is reloading a standard action or a full-round action? At this point, it starts being a somewhat severe impact to the character. I'd say you handle this by saying, "You can reload X times with standard actions." Maybe spend 1 power point per reload, treating them like a power feat.
Does reloading take multiple rounds? If it takes this long, keeping your character out of combat for the duration, I'd argue in favor of it being a bigger issue than simply a power that stops after a few shots. I'd be in favor of it being -3 points/2 ranks (round down) instead of -1 point/rank.