Question Can I justify this?

I don't see why you couldn't do such a thing with a straight up energizer. Instead of just having a straight up pipeline to their 'outside' power source as is standard, they have a slightly more complicated staged/turbo set up. Under normal conditions, the power flows through the main line on a normal draw. In special cases, the power it tapped into a side system which creates a sort of 'turbo charging' of the normal line, that instead of just letting it flow, its actively drawing it in allowing the abilities to more aggressive use/performance. And this could work on several tiers, with the upper tiers of the power being able to draw more than is typically safe... which would result in a burn-out like condition. And, of course, there's nothing stopping you from tying this to rage/aggression or whatever else you want to... it probably would become increasingly uncomfortable to use (especially if upper tiers actually damage the body instead of just straining it beyond normal comfortable levels)... and its not uncommon to need strong emotional context to work through that sort of discomfort or pain.