What is a rechargeable battery?

Rechargeable batteries are available in different types.
The oldest types are based on lead-acid or nickel-cadmium (NiCD).
Lead-acid for larger batteries and Nickel-Cadmium for smaller batteries.

Nickel-Cadmium has now been replaced by Nickel-MetallHydrid (NiMH) or Lithium battery with Cobolt (Li-ion CO), Polymer (Li-ion PO) or Manganese (Li-ion Mn).
Lead-acid battery in some different modes (wet, tube, AGM, Gel) remains stable on market but the lithium battery based on iron (LiFePO4) is now starting to be used more frequently.
We will mainly focus on batteries based on lead-acid but also a review of other commercial types will take place at the end of this document.

A lead battery consists of several cells. A cell is nominally 2V. Thus, for a 12V battery, 6 cells are required.
A main component of the battery is lead. The other main component is dilute sulphuric acid.
Mechanically, the battery cell can be built up in several ways.

Flat cell

A number of lead plates are mounted into a plastic container. Positive plates with a blend of lead dioxide (PbO2) and negative plates of porous lead. Positive and negative plates are place in a sandwich design. Between the plates, a glass fibre mat is installed which acts as an insulator. All positive plates are bind together with a power rail. Same goes for the negative plates. The positive power rail is then connected together with the next cells negative rail and so on until the desired number of cells and battery voltage is designed.

Tube cell

The tube cell differs from the plate cell through the mechanical design.
One large positive and one large negative plate are laid against each other with a glass fibre mat between them. Then the plates roll together like a roll cake. Finally, power rails are connected and the roller are mounted into the plastic container. The cells are internally connected in the same manner as for the flat cell battery.
Normally, tube cell batteries are delivered either as single cells or in 3-groups (6V) or 6-groups (12V).

Hardener

Lead is a soft metal. To make the lead harder, you add a hardener such as antimony or calcium. Today, there are different types of batteries that are adapted to different applications.

Battery types