Energy shield test station

Description
The Shield Tester is a small piece of machinery used by UNSC engineers to bring online inactive MJOLNIR armor shields, usually after a long time of inactivity. It appears in Halo: Combat Evolved and Halo 2, respectively in the Pillar of Autumn and The Armory. Both times it is used to bring online MJOLNIR energy shields, although it seems more a mere tester in Halo 2.

Function
First mentioned in the Halo: The Fall of Reach novel, during the MJOLNIR Mark Vs very first mission, this device gave charge to the armor's shield before they were actually activated by John-117, like a battery. However it seems that in both games they are only dormant, and are only brought back online. In Halo: Combat Evolved, the tester makes the same noise as a Plasma Pistol, possibly hinting that they were made using scavenged Covenant technology.

Since the MJOLNIR Mark V has an attached fusion pack on the back, it is unknown why the games require you to charge shields. Cryostasis may be a logical explanation to Halo 1, but the MJOLNIR Mark VI in Halo 2 had no such reason. In fact, the Mark VI variant didn't even have a fusion reactor.