Health and Energy Orbs cannot be collected –and therefore converted– while at maximum Health or Energy respectively.
The final converted restoration is rounded down. For example, with a rank 10 Equilibrium, collecting a Health Orb worth 25 Health will restore 27 Energy, rather than 27.5 Energy.[citation needed, may simply be UI rounding]
Health converted from Energy Orbs will not heal Companions.
Equilibrium stacks with Equinox's passive ability, which converts 10% of Health Orbs into Energy and vice versa, up to a total of 120% efficiency.
Since the mod is Uncommon, upgrading it past rank 6 will be costly for new or casual players. Upgrading the mod from rank 9 to 10 alone will require around 300 uncommon fusion cores and 400,000 credits.
Equipping a Companion that is prone to taking damage, such as Kubrows or Djinn, will enable Health Orbs to be collected even if the Warframe itself is at maximum health, allowing them to be converted into energy more readily.
This mod was awarded to players who survived at least 10 minutes in the Survival Weekend Event, which began on Friday August 30 @ 12pm EDT and ended Tuesday September 3 @ 12pm EDT.
When originally released, Equilibrium at maximum rank gave a flat +22 Health/Energy from the respective Orbs, regardless of the amount of Energy/Health picked up. This was later changed in Hotfix 9.7.3.
The Orbs in the mod picture show the pre-Update 16.0 Health and Energy Orb designs, which were simpler and not as animated as they are now.