It seems like several kills before the reloads stacks the energy you gain. However? It's still not good. It's like 2-3% per kill but seems to have a limit of about maybe 10-15%. That's base. Enhanced might make it better either gaining more perk kill or having a higher stack limit but of course it's bugged so we'll never know but unless this get's bumped significantly from normal to enhanced (which they rarely ever do) it still might not be that good. In theory with something like Rolling Storm on Palindrome it should be a great pair. Each Bolt Charge stack gives 2.5% melee energy for a maximum of 25% before needing to discharge it. Paired with Recycled Energy it should be a nice way to keep abilities up to keep discharging the Bolt Charge you build up. But Bungie being Bungie keeps shipping things out without proper testing and we're stuck with a half/fully dead perk until it gets addressed, which then usually takes another week or two or until the next Act to actually get a fix. If it gets fixed at all.