During E-CAT test run some hidden and unknown energy is being coming out in the form of heat energy in large quantity. Based on the principle of conservation of energy and from the well known nuclear fusion and fission reactions it is possible to guess that, the E-CAT hidden energy may be in the form of binding of protons and neutrons of the Nickel and Lithium atomic nuclei. By considering the nuclear binding energies of 58 28 Ni , 62 28 Ni and 7 3 Li an attempt is made to understand the energy liberation mechanism in E-CAT. With reference to the net energy production of (5825 ± 10%) Mega Joules liberated from one gram Ni of the E-CAT's 32 days third party test run, it can be suggested that, for every transformation of 58 28 Ni to 62 28 Ni via 7 3 Li , liberated heat energy is 3.64 MeV and for one gram of 58 28 Ni liberated energy is 5984 Mega Joules. For each transformation of 58 28 Ni to 62 28 Ni via 7 3 Li , 3 hydrogen atoms can be expected to be emitted. Note that, energy liberated for one gram of Nickel 58 in cold fusion is 1.66 MWh and energy liberated for one gram of uranium 235 in nuclear fission is 22.6 MWh. Clearly speaking, energy released in E-CAT is just 13.6 times less than the energy released in Uranium 235 fission.