Armor Shard

An Armor Shard is a pickup in Doom 3 that increases the player's armor rating by 5, to a maximum rating of 125. They are often found in abundance throughout the Mars base, usually grouped together. The higher the armor rating, the less health that will be lost in the instance of an attack.

They appear to be batteries of some sort which could mean that the Security armor must be powered in order to protect the user from attack.