What are the three essential parts to make a battery?

Question

Cell
reducing agent
acid
fuse
porous barrier or salt bridge
voltage regulator
oxidizing agent

Answer 1

I would say an oxidizing agent, a reducing agent, and a salt bridge/porous barrier. If you want to get technical I suppose you might add a cell (something to hold the oxidizing agent/reducing agent and the salt bridge).

Answer 2

1) oxidizing agent
2) reducing agent
3) salt bridge/porous barrier