Redstone mode: emit redstone signal if empty.
When the energy storage has some left over energy in it, but it cannot output that last bit of energy, should that be considered empty? or it must truly be 0 eu inside?
Not a bug, but rather almost useless if it requires the energy storage to be truly empty.
Along with this, if redstone mode is half-empty, might use the consideration of having energy stored more than the EU output rate instead.