4. The different concepts

The batteries we're talking about here differ from fuel cells in that they are self-sufficient generators. They are closed systems (with the exception of metal-air batteries and some seawater-primed batteries, which are generally reserved for either professional or military applications), with all their reactive products (oxidizing and reducing agents) contained within their own volume, and no reaction products escaping.

We can distinguish two main types of batteries (table 3 ):

• primed batteries, batteries in the common sense of the term, i.e. ready for use;

• primable batteries, reserved for special applications. As their name suggests, these require activation by triggering a suitable device.