[Moonman62]

You're thinking of fusion.

[Wonder Warthog]

"You're thinking of fusion."

Nope. Both fission AND fusion work because mass is converted to energy. In the case of fusion, the final fused atom weighs less than the two smaller atoms that were "fused"---that weight difference is the amount of mass converted to energy

In fission, the sum of the masses of the two atoms formed by the fission process is less than that of the original single fissionable atom. The weight difference again is the amount of mass converted to enery.

[tet68]

Of course the batteries would be lighter, all the light
will be out of them !

Haha.

[WildTurkey]

You're thinking of fusion.

Fission is also an example of conversion of mass to energy:

E=MC²

So is burning gasoline in your car ...