Energy Cells
Small, non-rechargeable "super-batteries", used to power plasma rifles, H.U.L.C. armor and other high-tech gear. Using fusion technology beyond the capabilities of modern Ikaanos, humans on Raana rely for these on the old Earth stock that's frequently delivered from the Mastersphere to certified vendors on Emerald Island.
Not readily available in shops, you can find them occasionally while scavenging (assign NPCs with the Techie &/or Scavenger trait to the Scavenger role if you want a steady supply). They sell for $50-$200 depending on economic conditions in Ikaanos, or you can keep them in hopes you'll find something advanced enough to require them.
Notes
Variables: aenergy
Links: technology, power, plasma rifle, scavenging, power cores
Source: Updated for MoR Version 0.8.5+