For automotive applications, there are basically three types of batteries: conventional, maintenance-free, and recombination.
Conventional Batteries
A 12-volt automotive battery contains six cells. In each cell is a series of alternating positive and negative plates, between which are isolator or separator plates to keep them apart. All the negative plates in the battery are connected, as are all the positive plates. Each plate has a grid construction, and to this grid, the plate’s active material – sponge lead – is bonded. The plates in each. cell are covered with a solution of distilled water and sulfuric acid (electrolyte). As the battery discharges (supplies electricity), the acid in the electrolyte reacts with the active material in the battery plates, forming lead sulfate and weakening the electrolyte solution. Conversely, as the battery is charged, the acid is returned to the solution, thereby strengthening it, and the used portion of the lead sulfate is converted back into active material in the plates. During this process, hydrogen and oxygen molecules are off-gassed out of the electrolyte, which is why a conventional battery often needs topping up with distilled water. The charge and discharge cycle also means that some lead sloughs off the plates. Over time, this builds up in the bottom of the case, reducing the overall capacity of the battery fluid. When enough material builds up, the plates will short out, and you’re stuck with a dead battery.
Maintenance-Free Batteries
