Energy Crystal (IndustrialCraft 2)

The Energy Crystal is a rechargeable energy storage unit similar to an RE-Battery or Lithium Battery. It can hold 100,000 EU. It requires an MV-tier interface to charge. Right clicking an energy crystal will NOT cause it to recharge electrical powered items in your inventory.

Recipe
When GregTech is enabled, the following recipe is also available:

Uses
The Energy crystal is used as a power storage unit much like an RE-Battery.

It is also used as a crafting ingredient for MFEs, Nano Armor, Lapotron Crystals, and other second-tier electric items.