Green Mana Battery (4ED) from Fourth Edition, available at 401 Games Canada.

• Rarity: Rare
• Finish: Normal
• Artist: Christopher Rush
• Card Text:
  2, T: Put one charge counter on Green Mana Battery.T: Add G to your mana pool and remove as many charge counters as you wish. For each charge counter removed from Green Mana Battery, add G to your mana pool. Play this ability as an interrupt.