The Battery: A Technical View

Often taken for granted, batteries make up a large part of modern technology. Most technological focus is directed toward how many pixels the new camera has, how much storage is in the latest MP3 player, and how fast the best laptop computer is. However amazing, all of these devices contain batteries of one kind of another. When dealing with batteries, it is important to recognize and understand the meanings of their labels. Being able to do so will allow a user to easily determine if batteries can be interchanged, determine which batteries last longer than others, and determine how these batteries should be charged.

How a Battery Works

The first thing to know about batteries is how they work. There are many types of batteries on the market, but almost all of them operate on a simple principle. A battery consists of two electrodes separated by an electrolyte. One electrode is less reactive than the other and is designed to be consumed. Inside the battery, the more reactive electrode attracts ions from the electrolyte. As this happens, the less reactive electrode is dissolved into the solution to replenish these ions. When these ions “plate out” onto the reactive electrode, they lose an electron. It also takes an electron to dissolve another ion into solution. This ion-exchange creates movement of charge, or current. These electrons are conducted through the electrodes and to the terminals of the battery, producing the battery’s available power. Once the less reactive electrode is used up, the battery has lost all of its charge. It must either be recharged by forcing electrons into it to reverse the process or thrown away if it has not been designed to be recharged.

Battery Acid

Usually referred to as “battery acid”, the electrolyte of a battery will sometimes leak out and corrode anything it comes in contact with. Contrary to popular opinion, the alkaline cells found in almost every non-rechargeable electronic gadget do not contain this mythical “battery acid” at all. This is simply a connotation to the lead-acid cell which can be found today in the form of a car battery. Lead-acid cells use sulfuric acid as the electrolyte. Alkaline cells use potassium hydroxide as the electrolyte, making them basic (or alkaline) as opposed to acidic. This is why these cells are called “alkaline cells”.

Voltage and Current

The amount of energy a battery can hold is stated by two specifications: The voltage and the “current draw per time” rating. Current draw per time is often stated as milliamp-hours (mAh) or amp-hours, with the mili- prefix indicating a thousandth of an amp-hour. The current draw time rating is simply a statement of how much energy can be stored in the cell. For example, if a battery is rated at 15 volts and 100mAh, this means that the battery can supply 100 milliamps of current at 15 volts for one hour before it is depleted.

Since most electronic devices require a specific voltage, the current draw per time rating will indicate the longevity of the battery pack. For instance, a device which operates on 5 volts will last longer using a 200mAh battery than with a 100mAh battery. Remember that voltage is not interchangeable – using a battery with an improper voltage in any electronic device will most certainly damage it. Note that an alkaline AAA cell and a D cell both supply 1.5V. However, the D-cell will last longer because it has a much higher current per time rating. This means that it is perfectly possible to replace AAA cells with the same number of D cells in any electronic device to make it last longer. However, this comes at the expense of weight and size.

Rechargeable Batteries

Rechargeable batteries come in many sizes and compositions. Care must be taken when charging them as the use of an improper charger will often cause the batteries to overheat and possibly explode. Some batteries require a charger which can sense the characteristics of the electrolyte and adjust charging power accordingly. Fast chargers usually have some sort of feedback mechanism to slow charging as the battery heats up. Always follow the instructions that come with batteries to achieve their optimum lifespan.