Onyx - Mjolnir

The last time he had worn it [MJOLNIR] was when he had greeted the Alpha Company recruits. Since then he had meticulously cared for it, and learned everything there was about its maintenance. Its fusion pods had been refitted when Kurt had been assigned to recon Station Delphi, so it had sufficient power for fifteen years of continuous operation.

- Halo: Ghosts of Onyx, Chapter 14