Chemistry – Lead Acid

Lead Acid Battery Chemistry.

If you already know about the Basics of Battery Chemistry then feel free to skip this page. This is for the person who knows nothing or next to nothing about Battery Chemistry. This is by no means a complete content of all things Chemistry and Lead Acid really just a primer.

Lead–acid battery – Wikipedia, the free encyclopaedia

The lead–acid battery was invented in 1859 by French physicist Gaston Planté and is the oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio, its ability to supply high surge currents means that the cells have a relatively large power-to-weight ratio. These features, along with their low cost, makes it attractive for use in motor vehicles to provide the high current required by automobile starter motors.
 

Basics of Battery Chemistry

Anode, Cathode and a Electrolyte

As some were taught in high school chemistry, atoms are the basic building blocks of matter. Atoms themselves are made up of a central Nucleus of positively charged protons and electrically neutral neutrons. Atoms also contain negatively charged electrons, which orbit the nucleus and are held in place by a strong electromagnetic force.

Atom image

Categories of Battery
Batteries are categorised into two major classifications: primary batteries, like the consumer grade alkaline units by various manufacturers. These kind of batteries are non-rechargeable once they have been discharged, they cannot be reused. Secondary batteries, are fully rechargeable. Batteries that fall into this category include, lead-acid, nickel cadmium, nickel-metal hydride and of course Lithium-Ion

How the Batteries Work
Batteries use a chemical reaction to generate Electrical energy. When atoms are combined together, they form molecules. For example, when two atoms of oxygen and one of hydrogen are combined, the resulting molecule is H20, or water.

Similarly, in some cases when one type of molecule comes in contact with a different type of molecule, they recombine to form a new molecule. This process is called a chemical reaction.

There are many types of chemical reactions, ranging from simple synthesis combinations, like the previous water example to much more complex including displacement, decomposition, and even combustion.

In some cases, a chemical reaction not only results in a new chemical molecule, but also causes the release of one or more of the electrons from the atoms. This latter type of reaction is the basis of how batteries operate.

If we cut open one of these batteries, we would find a series of vertical metallic plates, each separated by a small distance from the next, and immersed in a liquid solution, this is called the electrolyte. Some of the plates are made from Castings of lead dioxide, and others are from a spongy metallic lead material. The lead dioxide plate is know as a positive plate and the spongy lead is known as the negative plate.

Below is a video on the making of deep cycle batteries.

http://www.youtube.com/watch?v=eVJII8lIkZE

What is Difference between Deep Cycle Batteries and normal Lead-Acid car batteries?
Both car batteries and deep cycle batteries are lead-acid in use the exact same chemistry to operate. The difference is in the way in which the batteries optimize their designe.

A Car Battery.
These are designed for large amount sof current for a short time. This high current is needed to turn the engine over during starting. Once the ICE (Internal Combuston Engine) starts the alternator provides all the power that the car needs, so a car battery may go thorugh it’s entire life without ever being drained more than 20% of its total cpacity. To achieve a large current, a car battery uses thin plates in order to increase its surface area.

Deep Cycle Battery
These type of batteries provide a steady amount of current over a long period of Time. A deep cycle battery can provide a surge when needed, but nothing like the surge a car battery provides. a deep cycle battery as per its name is designed to be deeply discharged over and over again, this would kill a standard car battery very quickly. To accomplish this, a deep cycle battery uses thicker plates.

A car battery normally has two ratings:

  • CCA (Cold Cranking Amps) – This is the number of amps that the battery can produce at 32 degrees F (0 degrees C) for 30 seconds.
  • RC (Reserve Capacity) – The number of minutes that the battery can deliver 25 amps whilst keeping its voltage above 10.5 volts.

Deep Cycle Categories:

  • Flooded (FLA)
  • Valve-regulated lead-acid (VRLA) and these further divided into
    • Absorbed Glass Mat (AGM)
    • Gel

Normally, a deep cycle battery will have two or three times the RC of a car battery, but will deliver one-half or three-quarters to CCAs. In Addition, a deep cycle battery can withstand several hundred total discharge/recharge cycles, while a car battery is not designed to be totally discharged at all.

EVwest did a fantastic show in which Jehu Garcia did an extreme my informative session on batteries around time stamp 34:25

http://youtu.be/8KJr66bDxH8

 

For Information on Lithium Ion Deep Cycle Batteries. See the Page Chemistry – Lithium Ion

 

 

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