How Lead-Acid Batteries Work
If you are planning on adding a green electrical or energy
system in your home like solar panels or if you are simply
curious as to how your car battery works this article will go
through a basic understanding of the lead-acid battery and
how it functions to store and provide you with the
electricity that you need, when you need it.
Deep cycle lead acid batteries are the simplest as well as
the oldest battery. It was actually invented back in the
19th century and you will most commonly see it used
under the hood of cars and trucks, making it the ‘bestselling batteries.’ These batteries are very heavy
because they are packed with lead and lead-oxide sheets which are both very dense materials. While
they are old and do represent a serious environmental risk if disposed of incorrectly, lead and lead oxide
are plentiful in nature and making the effective battery cheap to produce. This is why 19th century
technology is still so popular.
The lead and lead-oxide plates alternate throughout the layers inside the battery. The plates sit in a
bath of sulfuric acid. A current flows from the led oxide cathode (positive plate) to the lead anode
(negative plate) meaning that the lead gives up electrons which the lead oxide accepts. The exchange
effectively turns both plates into solid lead sulfate. One pair of plates makes up about 2 volts so to
make 12 volt battery used in a motorcycle 6 pairs of plates sit next to each other inside the battery to
make up the 12 volts.
Now that you understand the basics of the chemical reaction let’s talk about the engineering. Batteries
can be broken down into energy or power. Batteries will be optimized to be either high power (release
large amounts of energy quickly) or high energy (they can store large amounts of energy and release it
for a long period of time).
The two different style batteries have unique applications in which they excel. The battery that you see
in your car will be a high power battery because a short but powerful burst of energy is needed to start
your car. The short burst is really all that it is good for. When you use the battery a light layer of lead
sulfate builds up between the lead plate and the lead oxide plate. If you run your car battery to zero
charge a few times (leaving the lights on) the lead sulfate will build up to the point where the electrons
can no longer transfer and battery is ‘dead’.
The battery that you would use if you had
Helios 255 watt panels on your roof for a
solar energy system would be high energy
so you can store more energy and release it
slowly with use. More specifically you
would use a deep-cycle battery which is
designed to be regularly discharge for 50-
80 percent of its capacity without
destroying the battery. Deep cycle
batteries will have thicker electrodes (than
a car battery) for increased energy density
and be spaced farther apart. The extra
space allows the sulfate debris that builds
up to fall down below the plates into a
storage area. Deep cycle batteries are
larger, heavier, and give off a lower current
than a car battery.
The lifespan of lead-acid batteries varies greatly and is based on a number of factors. The first is the
style of battery as discussed above; high power or high energy. The quality of the materials and
manufacturing also plays part in the lifespan of a battery but ultimately the largest decider in a batteries
lifespan is its use and maintenance. Heavily abused batteries in a car by people who don’t know better
won’t last long while a larger, well maintained battery on a yacht can last twelve years.
Photo Credit: Racingmix, St Stev,