Portable, self-contained electrochemical power source that consists of one or more voltaic cells. Can be stacked to produce a voltage the sum of the voltages of the individual cells.

A 12V automotive battery consists of six voltaic cells in a series, each producing 2V.

The most common primary (nonrechargable) battery. The cell reaction can be complex.

Anode is powdered zinc metal immobilized in contact with a concentrated solution of KOH

The cathode is a mixture of MbO₂ and graphite, seperated from the anode by a porous fabric.

NiCad: most common rechargable portable battery but are dense and toxic.

NiMH long lasting batteries that are not toxic

Li-ion: lightweight battery used in cell phones; has a high energy density

Fuel cells are not batteries because they are not self-contained systems; the fuel must continuously supplied to generate electricity.

Many fuel cells require much higher temperatures to operate, so a catalyst usually speeds up the reaction.