How lead acid batteries work

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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.

Background 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.

Chemistry 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.

Engineering 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 5080 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.

Lifespan 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,


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