A nine-volt battery, the most common of which (and the one referred to here unless otherwise stated) is designated a PP3 battery, is shaped as a rounded rectangular prism. 9-volt batteries are commonly used in pocket transistor radios, smoke detectors, carbon monoxide alarms, guitar effect units, and radio-controlled vehicle controllers. They are also used as backup power to keep the time in digital clocks and alarm clocks.
Nine-volt alkaline batteries are constructed of six individual 1.5V LR61 cells enclosed in a wrapper. [1] These cells are slightly smaller than standard LR8D425 AAAA cells and can be used in their place for some devices, even though they are 3.5 mm shorter.
As of 2007, 9-volt batteries accounted for 4% of alkaline primary battery sales in the US. In Switzerland as of 2008, 9-volt batteries totalled 2% of primary battery sales and 2% of secondary battery sales. [2] [3]
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The connector (snap) consists of two connectors: one smaller circular (male) and one larger, typically either hexagonal or octagonal (female). The connectors on the battery are the same as on the connector itself; the smaller one connects to the larger one and vice versa.[4] The same connector is used on most other battery types in the Power Pack (PP) series. The battery has both terminals on one end. The circular terminal is the positive pole; the hexagonal terminal is the negative. Battery polarization is normally obvious since mechanical connection is usually only possible in one configuration.
A problem with this style of connector is that it is very easy to connect two batteries together in a short circuit, which quickly discharges both batteries, generating heat and possibly a fire. The clips on the nine-volt battery can be used to connect several nine-volt batteries in series to create higher voltage.
The PP3 appeared when portable transistorized radio receivers became common, and is still called a "transistor" battery by some manufacturers. The Eveready company claims that it introduced this battery type in 1956. [5] Early transistorized radios and other equipment needed a low voltage battery, but the lowest voltage commonly available, small battery at that time was a 22.5V battery made for vacuum tube/thermionic valve radios. The 22.5V voltage was at the upper limit of the transistor voltage ratings, and it was clear that what was needed was a battery of lower voltage and high enough capacity to run the transistor radios for a reasonable time.
These batteries are commonly named 9-volt, and also colloquially named PP3, Radio battery, Square (sic) battery, and Japan "006P".
They all have a rectangular shape; the dimensions are height 48.5 mm, length 26.5 mm, width 17.5 mm. Both terminals are at the small end and their centres are 12.7 mm apart.
Inside an alkaline or carbon-zinc 9-volt battery there are six cells, either cylindrical alkaline or flat carbon-zinc type, connected in series. Some brands use welded tabs internally to attach to the cells, others press foil strips against the ends of the cells.
Rechargeable nickel–cadmium (NiCd) and Nickel-metal hydride (NiMH) batteries have between six and eight 1.2 volt cells. Lithium versions use three 3.2 V cells - there is a rechargeable lithium polymer version. There is also a low self-discharge NiMH version.
Formerly, mercury batteries were made in this size. They had higher capacity than carbon-zinc types, a nominal voltage of 8.4 volts, and very stable voltage output. Once used in photographic and measuring instruments or long-life applications, they are now unavailable due to environmental restrictions.
| Type | IEC name1 |
ANSI/NEDA name2 |
Typical capacity (mAh) |
Nominal voltage | |||
|---|---|---|---|---|---|---|---|
| Primary (disposable) | Alkaline | 6LR61 | 1604A | 565 | 9 | ||
| Zinc–carbon | 6F22 | 1604D | 400 | ||||
| Lithium | 1604LC | 1200 | 9.6 | ||||
| Rechargeable | NiCd | 6KR61 | 11604 | 120 | 7.2 | 8.4 (some) | |
| NiMH | 6HR61 | 7.2H5 | 175-300 | 7.2 | some:3 | ||
| 8.4 | 9.6 | ||||||
| Lithium-ion polymer | 520 | 9 | |||||
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An alkaline battery that is unused or used with extremely low power consumption devices (transistor leak current, etc.) can be expected to last approximately for 6 years, essentially the shelf-life of a new battery.
Lithium 9-volt batteries are consumer-replaceable, high energy density batteries designed to last up to 5 times longer than alkaline 9-volt batteries and up to 10 times longer than carbon-zinc 9-volt batteries in many applications. In addition, lithium PP3 batteries have a long shelf life of up to 10 years. Common applications for lithium 9-volt batteries are smoke / CO (Carbon Monoxide) alarms, and electronic parking meters.
There are other nine volt batteries, such as PP7 and PP9. These date from the days of early transistor radios and are now less common than PP3. In the days of valve radios which used batteries designed specifically for vacuum tubes, there was a nine volt grid bias battery which had tappings for various voltages between 1.5 and 9.
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