User blog comment:101stranger/Ah, the wonderful world of UNSC infantry weapons/@comment-923138-20100405220538

Yes, but they run off other sources, fusion packs, if I remeber correctly. Since the Mark VI was designed to charge up faster, a upgrade that would charge up instanteously would essentially make the wearer invincible until the fusion pack was depleted. So my suggestion is to allow aqquiring of additional packs to make sure your shield can last longer. But this would have to go along with a higher damage rate to compensate.