User Manual

6
water, sometimes called battery acid. When an electrical load
is placed across the battery’s terminals, a chemical process
starts inside the battery that produces electrical energy.
Battery Capacity. The size and number of plates within each
cell have a direct relationship to battery capacity, or its ability
to start engines of various sizes. Cranking current capacity (or
fl ow of electrical energy) increases as the plate surface area
increases. Directly related to plate size, is the amount of active
material on each plate (lead peroxide on the positive plate
and metallic sponge lead on the negative plate). The battery’s
current producing capacity is directly related to the amount of
active material on its plates.
Battery Chemistry. Batteries are constantly either discharging
or charging, and during either process, ions (both positively
or negatively charged) are transferred from the positive and
negative groups of cell plates. The plates are insulated from each
other with a permeable, non-conductive material which allows
this transfer of ions. At the same time as the ions are moving
from one plate to another, the ratio of battery acid to water is
changing as well. However, as the battery discharges, the ratio of
acid to water changes so that there is less sulfuric acid and more
water; thus, the specifi c gravity (SG) of the electrolyte solution is
lowered as well. SG can be used to measure a battery’s state-of-
charge. For example, an SG of
1.160 indicates a battery with only a
50% charge. The process is reversed when the battery is charged.
Battery Construction and Chemistry
Technically speaking, a battery is a device that converts
chemical energy to electrical energy. It’s important to
understand that a battery does not “store” energy, or electricity,
it stores a series of chemicals, and through a chemical reaction
electricity is produced.
What’s Inside the Battery Case? To understand the process of
chemical to electrical energy conversion, let’s take a look inside a
battery. The battery case is divided in sections called cells with a
12-
volt battery having six cells that produce
2.2 volts each (depending
on battery type) for a total of
13.2 volts. A 6-volt battery has only
three cells with a total voltage of just over
6 volts.
How Battery Cells Work. The cells consist of lead plates,
half of which have a positive charge and the other half with
a negative charge. Within each of the cells the plates are
stacked alternately: negative, positive, negative. Insulators or
separators (usually made from fi berglass or treated paper) are
placed between the plates to prevent contact. The alternating
plates in each cell are connected at the top to form two groups,
one positive and one negative. Each cell’s groups of plates are
then connected in series (positive to negative) to those in the
next cell. The “active material” in these positively and negatively
charged groups of plates produce electricity when immersed
in an electrolytic solution that is made up of sulfuric acid and
Here is what an AGM Yuasa battery looks like with the cover removed. The case is divided into 6 cells each, containing plates and separators.
Cells are inner connected by lead lugs on top of each cell. With the cover in place, only the positive terminal (right side) and negative terminal
are visible. At the lower right is the strip of sealing caps that will be installed when the battery is fi lled with electrolyte. Once installed, never
remove the sealing caps to add water or electrolyte to the battery during its service life.