The Geothermal Generator is an upgrade to the Generator added by IndustrialCraft 2. It can supply IC2 machines with Energy Units (EU) or charge tools and batteries in its GUI. The Geothermal Generator uses Lava to generate EU; it will take Cans, Tanks of any type, Cells, or Buckets. The first two can be used to store Lava and are thus more preferable. The Geothermal Generator outputs 20 EU/mB per tick.
To charge a tool such as a Diamond Drill, right-click with no items equipped to open its GUI and place the rechargeable item in the upper slot. It can also be upgraded to the Thermal Generator if GregTech is installed.
This cannot charge a Lappack or anything of a higher tier.