Damage resistence? if you mean how much shielding you get per point of energy that's actually really easy. here,
ArcShield
{
Type = ArcShield
Radius = 7.5
Arc = 90d
DrainAmmoFrom = BatteryStorage
AmmoDrainPerDamage = .5
Rotation = -90d
Location = [1, 1.5]
"AmmoDrainPerDamage = .5" is what you want, Basicly the standard amount is 2 "shield hp" per energy point. If you change it to say .25 then it'd be 4 points or instead of the normal shield having (6k energy = 12k shield) would have (6k energy = 24k shield).