9v Batteries
The nine volt battery is also known as the PP3 battery and follows the ANSI (American National Standards Institute) standard 1604A. Unlike the common A-batteries, the 9v battery is not cylindrical; it is instead shaped in the form of a rectangular prism. The dimensions of the 9v battery are 48 millimetres × 25 millimetres × 15 millimetres (1.9 inches ×1 inches × 0.6 inches).
The 9v battery is today used in a wide range of different electronic devices, such as personal alarms and smoke detectors.It can trace its history back to the era of the first mass-produced transistorised radio receivers and the Missouri based American Energizer company (Energizer Holdings) claims that they released the first 9v battery on the market in 1956.
Since the 9v battery has been so widely used in transistorised radio receivers, it is often referred to simplay as “transistor battery”. The 9v battery can be used to start a fire if you find yourself in a situation where you have no matches or lighter, but a 9 volt battery and some steel wool. By rubbing the steel wool against the contacts of the 9v volt battery, you will create sparks strong enough to light up a fire.
Unlike the cylindrical A-series batteries, the rectangular 9v battery will have both the positive and the negative terminals located in the same end of the battery. The negative terminal consists of a snap fitting that will connect (mechanically as wells as electrically) to a mating terminal on the power connector. The power connector is equipped with a similar snap fitting on the positive terminal which mates to the 9v battery. This means that it is very easy to connect a 9v battery to an electrical appliance correctly, since only one configuration will be practically possible.
If you would open up a rectangular 9v battery you would find six 1.5 volt cells arranged in series. (Due to safety reasons, you should however always refrain from opening batteries or breaking the protective container in any way.) The cells in the 9v battery can be either similar to AAA cells, i.e. long and cylindrical, or be flat and rectangular. Even though the PP3 9v battery always has the exact same dimensions regardless of manufacturer, the constituent cells can actually vary in size from producer to producer. You can for instance notice how some manufacturers use slightly shorter cells. The way the cells are joined together inside the battery can also very depending on manufacturer. Some manufacturers prefer to use soldered tabs, while others instead place strips of foil against the ends of the cells.
A traditional way of testing if a 9v battery still contains any useful charge is to press the two contacts against your tongue. If you feel a minor “sting”, there is still useful charge left in the battery. The unpleasant, but essentially harmless, sensation is caused by current passing from one part of the battery to the other through your tongue. Licking batteries is however not really a good habit and investing in a proper battery tester is safer; especially if you have small children around that you might not wish to learn that the 9v battery, and other electric devices, is something that you put in your mouth.
In addition to the common alkaline 9v battery, you can today purchase a wide range of other 9v battery types, such as the NiCd 9v battery, the NiMH 9v battery and the lithium 9v battery. The abbreviation NiCd stands for Nickel Cadmium, while the abbreviation NiMH means Nickel Metal Hydride. When you purchase your 9v battery you will also need to make a choice between the rechargeable and the non-rechargeable 9v battery.
