Energy Shielding (D20 Modern Equipment)
From D&D Wiki
Some armor in the Halo universe possesses personal energy shielding — simply put, a barrier of energy that surrounds the wearer of the armor (or in some cases, the spaceship).
Energy shielding has a "store" of hit points that are reduced by hits and a "recharge rate", that determines how fast the energy shielding recharges. When the energy shield takes damage, it's store of hit points are reduced. When it's hit point score reaches 0, remaining damage taken from the hit "rolls over" onto the wearer of the energy shield, and the wearer takes damage as normal from then on. One round later, at the end of each round (if the user took no damage in any form that round), the energy shield regenerates a number of hit points equal to it's "recharge rate".
Full-Body Energy Shield: This type of energy shield gives the wearer two normal Armor Classes: "Energy Shield AC" and "Normal AC". While the energy shield has at least 1 hit point, the "Energy Shield AC" is used. While the energy shield has 0 hit points, the "Normal AC" is used. The character's Flat-Footed AC is equal to his current AC minus his Dexterity modifier.
Partial Energy Shield: This type of energy shield does not add it's equipment bonus to the character's AC. Instead, if the attack roll to hit the character is less than the character's AC plus the equipment bonus to AC on the energy shield, but still greater than the character's AC, energy shield takes the damage instead of the character.
Energy Shielding is expressed as "Energy Shielding shield's Hp/shield's recharge rate"- for example: "Energy Shielding 22/5".