Lesson 2/Learning Event 1
We, as mechanics, must know a great deal about batteries to keep them in good working order.
Automotive batteries need daily attention from the operator plus some frequent maintenance
performed by the operator and the mechanic, as well as special attention under certain conditions.
To do your part, you will need knowledge of batteries and the procedures involved in their
A battery is nothing more than two unlike conductors immersed in a special solution called
You can make a battery in a few minutes if you have a lemon, a paper clip, and a piece of
uninsulated copper wire. Here is how it is done:
Straighten out the paper clip and cut the copper wire so it is the same length as the paper
clip. Stick both the clip and the wire deep into the lemon so they are close together but not
touching. Now, if you touch the free ends of the wire and paper clip to your tongue, you
will experience a slight tingle and a metallic taste.
The tingle and the metallic taste are due to electrons passing through the saliva on your
tongue. The lemon juice is the electrolyte solution; the steel paper clip and the copper wire
are the two unlike conductors. Action of acid in the juice combining with the conductors
causes an excess of electrons to build up on one conductor. When you touched your
tongue to the conductors, you closed the circuit and electrons began to flow.
Almost everyone is familiar with the common flashlight battery (dry-cell battery).
The battery consists of a zinc cup-like container that is sealed at the top. A carbon rod is set in the
middle of, and insulated from, the container. The rod extends out the top with its exposed tip
covered by a metal cap. The cup is filled with a mixture of materials that make up a paste-like
electrolyte. The carbon rod and the zinc case are the unlike conductors, with the case containing
the negative charge and the rod the positive.
A good flashlight battery has an electrical charge of 1 volts. As the battery is used, the voltage
gets lower. Finally, it reaches a point where it no longer furnishes enough electrical power to do
the job right and must be replaced. The battery is then said to be discharged or run-down.