Alkaline Batteries are all over the place: in our cars, our PCs, laptops, portable MP3 players and cell phones. A battery is essentially a can full of chemicals that produce electrons. Chemical reactions that produce electrons are called electrochemical reactions.
If you look at any battery, you'll notice that it has two terminals. Electrons collect on the negative terminal of the battery. If you connect a wire between the negative and positive terminals, the electrons will flow from the negative to the positive terminal as fast as they can. Normally, you connect some type of load to the battery using the wire. Inside the battery itself, a chemical reaction produces the electrons. The speed of electron production by this chemical reaction (the battery's internal resistance) controls how many electrons can flow between the terminals. Normal batteries have generally 1.5V per cell voltage (except some Lithium cells which have 3V voltage). The batteries which have higher voltage output are built generally from many 1.5V cells in series all put inside same "case". Since there are no real industry standards, many terms used by battery manufacturers have become misleading marketing hype.
Although the terms battery and cell are often used interchangeably cells are the building blocks of which batteries are constructed. Batteries consist of one or more cells that are electrically connected.The world of batteries divides into two major classes: primary and secondary batteries. Primary batteries such as the common flashlight battery are used once and replaced. The chemical reactions that supply current in them are irreversible. Secondary batteries (for example, car batteries) can be recharged and reused. They use reversible chemical reactions. By reversing the flow of electricity i.e. putting current in rather than taking it out, the chemical reactions are reversed to restore active material that had been depleted. Secondary batteries are also known as rechargeable batteries, storage batteries or accumulators.
As a battery is used, the amperage is consumed and the voltage drops. There is a formula for a ballpark estimate for battery life:
Estimated total battery life = (Ib / Id) x 0.7
Where: Ib = Total Capacity Rating of battery (mAh) and Id = Current Consumption of the device in milliamps (mA)
Use of this formula does not guarantee that you will get the determined battery life. Other factors such as weather condition (temperature, humidity, etc.), and battery condition can extend/shorten the battery life. This formula cannot be used to calculate battery life for alkalines. Battery state can be somewhat determined with the battery voltage. Please note that batteries do not show their correct voltage unless under a load. Battery testers are designed to provide this load; however, when testing batteries with a multimeter, you must have the meter set to measure DC voltage and place the battery under load by using a resistor in parallel with the test leads of the meter. How the battery voltage drops during the use varies from battery type to another.
Alkaline batteries are single-use batteries, but provide a higher start voltage and longer life than many other single use batteries. The capacity rating for alkaline batteries is not a fixed number on alkaline batteries, although it can be safely assumed that an alkaline battery will last significantly longer (2-3 times as long) as a same-size rechargeable under the same conditions. Alkalines do not have a fixed capacity rating because where the discharge rate of rechargeable batteries is a straight line, the discharge rate for alkalines slopes depending on the current drain. The higher the current drain, the faster the battery discharges. In alkaline batteries, the sloping discharge curve makes it impossible to accurately provide a mAh rating; the rating would vary depending on discharge rate and temperature. Alkaline batteries are significantly heavier than many other battery types for the same size, but they can store lots of energy (few times more than "regular" batteries). Alkaline batteries can take storage nicely when not used. Alkaline batteries stored at "room temperature" self discharge at a rate of less than two percent per year. However, if alkaline batteries are stored at higher temperatures they will start to lose capacity much quicker. At 85 degrees F they only lose about 5% per year, but at 100 degrees they lose 25% per year.
There is a variation of alkaline cell that can be charged with a limited number of times: Rayovac sells rechargable akaline batteries. Rechargeable alkalines are really just normal alkalines with a beefy casing to reduce leakage, but the full charge drops off significantly even after the first recharge cycle and gets worse from there.