The E-Recovery Tank is a new powerup in Metroid: Other M. There are a total of three in the game. Each one found increases the amount of energy that Samus restores when using Concentration in a critical state by one Energy Tank. The number of E-Recovery Tanks in Samus' possession is indicated by a light blue border around it. It also increases the threshold for energy recovery, allowing Samus to restore her energy sooner. It does not increase the time needed to charge. They have a "purple" color.
"E-Recovery Tank: Increases the amount of energy you can restore through Concentration. The energy threshold required to make energy recovery possible will also increase."
This increases your CONCENTRATION restoration volume.