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DC connector

A DC connector is an electrical connector for supplying direct current (DC) power. DC connectors are poorly standardized, compared to domestic AC power plugs and sockets. DC plug is a common name used for one common type of cylindrical two-conductor plug available in a range of sizes and used to power small pieces of electronic equipment. It is also used to describe some older multi-pin plugs.

Several competing standards exist for DC plugs, and in some cases incompatible plugs will fit together, or can be made to fit, possibly damaging equipment if:

the voltage is wrong
the polarity is wrong
current ratings are exceeded
power supply filtering or stability is inadequate for the equipment being powered
non-matching connectors are forced together.

Cylindrical types

Also known as barrel connectors, concentric barrel connectors or tip connectors, small cylindrical connectors come in an enormous variety of sizes.

The intended use of these plugs is on the cable connected to a power supply. The matching jack or socket is then mounted in the equipment to be powered. Some of these jacks contain a normally closed contact, which can be used to disconnect internal batteries whenever the power supply is connected, avoiding the risk of battery leakage or explosion posed by incorrect recharging of the batteries.

Cylindrical plugs generally have an insulated tip constructed to accept insertion of a pin. The outer body of the plug is one contact, most often but not always the negative side of the supply. A pin mounted in the socket makes contact with a second internal contact. The outer plug contact is often called the sleeve, and while the inner one is called the tip.

There are a wide variety of different sizes and designs for these power connectors, and many appear quite similar to each other yet are not quite mechanically or electrically compatible. In addition to a plethora of generic designs (whose original designer is unknown) there are at least two different national standards—EIAJ in Japan and DIN in Germany, plus the JSBP connector used on some laptop computers. The Japanese EIAJ standard includes five different sizes, with each supporting a specified range of voltages. Most of the other coaxial DC power connectors have no specified voltage association, however.

The most common plugs are 5.5 mm in outside diameter (OD) and 9.5 mm in length. Two pin sizes are common in the jacks for this size plug body, 2.1 mm and 2.5 mm, and the plugs should ideally match. Generic plugs are often named for the pin diameter they are designed to take, so these types will be seen described as 2.1 mm DC plugs and 2.5 mm DC plugs respectively. These two sizes are easily confused unless seen together.

Contact ratings vary from unspecified (and probably less than 1 A in practice) up to 5 A ,with 2 A typical. Voltage is again often unspecified, up to 48 V with 12 V typical. The smaller types usually have lower ratings, both for current and voltage.

Snap and lock DC power connectors

These connectors look similar to Mini-DIN connectors, but have either 3 or 4 thicker pins and a slightly larger mating shell. Because of this they do not mate with any of the Mini-DIN connectors. They can usually be identified by an engraved symbol on the backs of the plug, consisting of two wide arrows pointing in opposite directions, but parallel to each other, or sometimes one wide arrow inside a box, pointing towards the end of the male connector.

Also known as Power Mini-DIN or Power DIN
The male plug's mating shell outer diameter is 0.394 inches, 10 mm and the pins is 1.5 mm diameter
Standard may include a limit of 20 V at 7.5 amps
3-pin

Hosiden part number TCP8927-53
Kycon part number KPP-3P (Obsolete) or KPPX-3P (RoHS)

4-pin

Kycon part number KPP-4P (Obsolete) or KPPX-4P (RoHS)

Molex connector

The connector design most commonly called Molex connector has frequently been used to supply DC power, most frequently on personal computers, for supplying power to drives and other peripherals.

Mini IEC connector

Access Communications Mini IEC diagram

Tamiya connector

Commonly used on radio-control (toy) vehicle battery packs and chargers.

Deans connectors

Popular with higher-end radio-control vehicle battery packs and chargers.
W.S. Deans Web site

JST RCY connector

Also known in RC circles as the BEC connector, or the P connector.

Locking Molex connector

Available in 3, 4, and 6 terminal configurations.

Inverter tabs - inverter lugs

Available in 2 and 4 gauge. Designed to pass very high amperages at voltages up to 600V DC to and from battery packs, inverters, and other high amperage loads to a terminal bus.

Airline in-seat power supply system

Two different airline in-seat power supply system (ISPSS) standards for DC power have been used in the past.

American Airlines has in the past used an automotive cigar lighter socket, but using 14.7 V instead of the automotive 12 V.

Most other airlines that provide DC power use the EmPower system, which has a 4-pin Hypertronics' D-series connector smaller in diameter and overall size than a cigar lighter plug.

Anderson Powerpole connectors

The Anderson Powerpole has been adopted by the amateur radio community as their standard 12-volt DC power connector for everything from radios to accessories. It is a bit more expensive than the older “standards” of the 2-wire trailer plug and Molex connector, but provides a more reliable electrical connection (both mechanically and electrically) and is easier to adapt to a wider range of wire gauges. Powerpole connectors are physically and electrically hermaphroditic, thus avoiding the need to worry about which end is the plug and which the socket, or which end has the correct polarity, as is the case with the physically but not electrically hermaphroditic 2-wire trailer plug.

For use in amateur radio, the community has adopted a standard polarity for assembling the Singlepole connectors, using one red and one black housing, as well as a mnemonic for remembering the arrangement: Red Right—Tongue Top. Before this polarity standard was adopted, some amateur radio groups had chosen the opposite polarity, so it is wise to double-check the polarity before blindly plugging devices together.

Although many sizes of the Powerpoles are available, the size most commonly used is the 15/30/45 amp variety. These sizes all use the same plastic housing, differing only in the metal contact inserted into the housing (selected based on the current need and wire size). Larger Powerpole connectors (the SB/Multipole series) with 2 or 3 contacts in one molded housing are commonly used in various industrial settings, including as a battery connection for some UPS devices, removable truck/Jeep winches, many electric forklifts, and other electric powered vehicles.

For the larger Multipole design, each color is keyed so as to mate only with a like colored connector, and Anderson publishes a list of recommended voltages for each color:

12 V: Yellow
18 V: Orange
24 V: Red

Used by Warn for its 12 V winches (should have used yellow multipole)
Used by Tripp-Lite for some of its 24 V external UPS battery packs

36 V: Gray

Used by Tripp-Lite for some of its 38 V external UPS battery packs
Used by APC for some of its 24 V external UPS battery packs (should have used red multipole)

48 V: Blue

Used by Tripp-Lite and APC for its 48 V external UPS battery packs

72 V: Green
80 V: Black
96 V: Brown
120 V: Purple
144 V: White

Some manufacturers have ignored this color coding recommendation. One should always test the connection with a voltmeter if unsure. For example, winch manufacturer Warn uses a red housing for its winches, even though they are powered by 12 V DC, not 24 V DC.

The connectors are also starting to be used by Radio Control hobbyists.

This connector design was created by Anderson, but the patent on its design has apparently lapsed, and there are other manufacturers of this connector now, including AMP and Sermos.

Cigar lighter sockets and plugs

The car cigarette lighter socket is technically called a cigar lighter receptacle, since it was originally designed as a lighter for cigars—hence its rather large size (and unheated center barely large enough to light a cigarette).

These sockets were not originally designed to provide DC power, and are not an ideal DC connector for several reasons, notably the fact that three sizes exist (one for 6 V DC and two for 12 V DC) and the mating of the different sized 12 V DC plugs and jacks is problematic. Because of this, and the small gauge wiring sometimes used, they can sometimes provide only unreliable and current-limited power connections.

The polarity for 12V DC sockets is center pin positive (+), outer collar negative (-). Reversed polarity will damage some electronic devices.

DIN 4165 connector

Similar in concept to an automotive cigar lighter, the DIN 4165 connector is shorter and smaller, and found most frequently on motorcycles.

Also known as Powerlet connector or BMW Accessory connector

XLR connectors used for power

In the broadcast, film and television industries, the 4-pin XLR connector is the standard for 12v power. The connectors are wired pin 1 negative, pin 4 positive. Often pins 1 and 2 will be negative, 3 and 4 positive for a higher current rating. Female connectors are used as supply and male connectors are used on loads. Most battery belts and power supplies output 13.2v, but equipment can usually handle a range of 11-18 volts to accommodate battery packs of varying voltages and charging while operating.

The readily-available XLR3 is also used by some manufacturers as power supply plugs despite their being a well-accepted standard for other purposes.

Other DC connectors

SAE connector
Fly RC magazine: Connectors Connection describes most or all of the connectors used by RC users.
There are a number of similar design PC board power connectors, including Molex Mini-Fit SR, Molex Mini-fit jr., MOLEX MICROFIT and Molex SABRE connectors, and AMP DUAC connectors that look similar to each other.
Some plugs with three, four, five or more pins are also called DC plugs. These were common on vacuum tube equipment and continue to be used where several voltages are supplied. On vacuum tube equipment the pins are normally on the equipment side of the join for safety reasons.
Many cell phones use DC connectors that are unique to the manufacturer.
Winchester Electronics has an interesting snap-on power connector that might be appropriate for this page.
Plastics One offers custom cable and connector manufacturing, primarially targeted at the medical and communications industries. If you find a DC connector not detailed elsewhere, there's a chance they made it.
ODU makes specialized industrial-grade connectors.
Article on battery-pack connectors.