That is actually wrong information, not your fault though I fell for it myself. Ender IO and most other 'RF' mods(there are exceptions) expect you to push the energy out yourself.
You need to expose your BaseEnergyContainer as a Capability for the connection to take place. And in the case of sending the message when it is right clicked (not sure if this has been solved already) you can create a getter method for your container field.