Game version := 1.7.10-Forge10.13.4.1614
Mod version := NuclareCraft 1.9f
Environment := Single player + Multi player

I put empty fluid cell in, and gave enough RF, as what recipe(provided by NEI) says. However, nothing happened.
I tried to add Energy Update and Speed Update, but it doesn't help.

Is it caused by an outdated recipe? Screenshots attached below.

As of version 1.8 or so, the Electrolyser requires water to be pumped into it as well as power - that little bar beside the input slot is the internal water tank.