12 Volt DC car adapter plug


The 12 Volt car adapter is a very popular source of DC power so its worth knowing more about its parameters.

12V adapter. positive and negative contacts labeled. Red arrow shows direction of rotation for access to the fuse under the positive contact.

20-25mm in diameter and 50mm long.

Positive contact at the tip and negative contact on the side.

The negative side contacts are usually attached to springs to hold the device secure.

Frequently one of the negative side contacts may be not electrically connected and simply to help hold the device in place.

Under the positive contact there may be a spring and a fuse, which is normally a 2Amp fuse.


Some adapters in this format may support 24 volts as some truck electrical systems are 24 volt.

12 Volt DC charger for laptops and other devices

This device will allow you to charge devices in the 15 -24 volt range at around 3 Amps.

12 V DC-DC charger with adapters for laptops and other devices 15-24 volts

This is a much more efficient way to convert stored energy in a battery to stored energy in you laptop( or to run another device) rather  than through an inverter.

When looking for one of these adapters  (which there are many designs)  look at the adapter tips to make sure they will fit the devices you intend to use it to power.

Make sure the voltage is switchable and matches the voltage you need for your devices.

Not every possible voltage is supplied, common voltages are:  15 16 18 19 20 22 24

Many devices are voltage tolerant to some extent, if need be 1 or 2 extra volts work, if you cannot supply the exact voltage.

Make sure the power rating of the adapter is more than the power rating of the the device.

Check the polarity of the device and charger, usually the outside shaft of the adapter is negative (-) whereas the tip or inside is positive(+). Some adapters allow polarity changes on the tips.

The rating for the adapter can be between 80 and 150 watts.

The easy way to determine the power rating is to look at the AC adapter of the device and multiply the DC voltage and current together and that will be the power rating.

Cost 80W  $25

Cost 150W $120

Cost of an obscure tip $3, time to find one, up to 6 months (be warned).

The sensation of success after a long determined hunt, priceless?

Charge a phone virtually anywhere kit.

well you’ll need a power supply like a 12V battery or a solar panel but with this equipment you have a lot of options.

12 Volt car socket from alligator clips.

iLuv USB car adapter

USB with 10 different phone charger connectors. ‘The octopus’

Make sense? I hope so.

so with these 3 items you are able to convert any 12 Volt battery (or 12 Volt solar panel) into a phone charger in a less than a minute.

cost of items about $25,being able to make that call or access that data, priceless?

Universal 12 volt car socket electricity

This device will allow you to connect to any battery with terminals and start extracting electricity and provide it in a relatively convenient and familiar 12V DC format.

The current rating of the car socket will be the bottleneck in this system 4 Amps(?) but it will allow you to tap into car batteries that you may encounter.

Black is negative (-) and red is positive (+), connect the negative terminal first. Do not allow the clips to touch each other one connected to a battery, even if it it through some other metal, conductive or wet material.

Any device that could normally be connected to a car socket can be connected to this. the car socket 12 volt connected is a very popular DC power format being able to access this format is very useful. A lot of household electronics is designed to run from 12 or less volts.y rule of thumb, if you can lift it easily by yourself its probably 12 volt capable.

cost about  $8 at better electronic shops and possibly some car accessory shops.

12 Volt car socket from alligator clips.

Universal USB power

iLuv USB car adapter

If you need USB power and you have access to a car or a car cigarette lighter plug that has power, this is precisely what you need.

I really liked how this example appears to be thumbing its nose at copyrights of Apple and Microsoft XboX.

Some models are tolerant of input voltages from 12-24 volts some are not.

Some models advertise what level of current they supply, 1 Amp is common.

Input 12V-24 DC output 5V DC 500-2100mA

these devices only supply power to the USB device not data, this device will not allow you to ‘download a car’ or some other wizardry.

Cost: about $10 for electronics and car accessory shops. Cheaper models may be available with lower output current.

Wizardry sold separately*

Universal USB phone charger

In the wake of the Japanese tsunami in march 2011 one of the first things people wanted to do after they had reached the safety was to recharge their phones.

Imagine being faced with many people all wanting to charge their phones at once. Despite the market dominance a a few mobile phone makers there is still quite an array of charger plug formats.

When i first saw this item i could see just how useful it was. I highly recommend it. It’s the most important part of my ‘charge a phone virtually anywhere’ kit.


Note while it has the correct connector for the Apple iPhone/iPad it may not work due to Apple’s proprietary hardware restrictions.

So you should look back in the box your phone came in, and find that weird cable with USB at one end and your phone connector at the other and keep it handy.

Most phones support charge via USB now, and even it you don’t use such a cable to connect to your computer its useful for charging.

Fast charging: you may find a 2.1A USB port occasionally and this will allow you phone to charge faster if your phone supports fast charge.

For the record USB is normally 5V DC 500mA, the fast charger works by shorting pins 2 and 3 the green and white wires to ‘tell’ the computer to supply more current, 2.1 Amps.

cost about $5-$8 available in some $2 style shops, may come with accessories like car to USB and AC to USB which are both worth paying a few extra dollars for.

USB with 10 different phone charger connectors. ‘The octopus’

Electrical Energy: The Inverter

400W 12V inverter with alligator clips and aluminum housing/heat sink. 240V 10A 50Hz

Simply put: the Inverter changes DC current into AC current.

Usually the voltage and frequency output are based on household AC but other voltage/frequency combos are possible.

Some inverters made for AC motors such as electric bicycles produce variable frequency 3 phase AC.

Because of the high current and voltage and current (240V 10A) produced by Inverters they are extremely dangerous.

Inverters are rated for a certain wattage output so when plugging in a device into an inverter check to make sure the inverters total wattage is not being exceeded.

Inverters usually make a alarm tone when they are running low on current, which is usually the sign the battery they are connected to is almost drained of current.

Inverters are quite inefficient with losses of 50% on inversion being typical.

If you have battery banks use DC wherever possible to effectively double your usable energy.

Some newer inverters are designed with a cigarette plug as the DC power connector.

these cannot be used for more than 150W rated devices because of the limitation of current flow through the cigarette plug.

For power consumption greater than 150W use large size alligator clips or heavy gauge battery terminal connectors.

Inverters are sold as square wave, modified sine wave or pure sine wave.

pure sine wave inverters are the most expensive and the extra expense (normally double the price of a modifies sine wave model of the same wattage) are only really noticed in some  Hi-Fi and television equipment.

If the device you are plugging into an inverter contains a rectifier, the exact shape of the wave matters less at the wave is being recitficed to DC, so a modiifed sin wave would be perfectly acceptable here.

square wave inverters are acceptable for very simple application such as incandescent bulbs.

Inductive load

Devices such as fluorescent lights and some devices with large motors such as some fridges have high inductive load and must be either modified before inverters are used or not used at all.

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grid connect


Energy Electrical: The Rectifier

Put simply; a rectifier changes AC electric current into DC electric current.

There are several designs increasing in complexity and parts, but all are based on four or more diodes and optionally a capacitor.

single phase rectifiers

4 diodes

Standard textbook diagram of a single phase rectifier. the ‘~’ symbol is for AC input.

A single phase rectifier diagram. Drawn in a slightly different, but functionally identical way.

3 phase rectifier

6 diodes

A 3 phase rectifier. Shows that any number of phases can be used by simply adding two more diodes.

Here’s one I prepared earlier:

red labeled wires positive,  brown/black labeled wires negative, 3 other wires green individual AC phases.

2 BR 354 rectifiers used to create a 3 phase rectifier. A recycled computer south bridge heat sink has been cable tied on.

Rectifiers produce some heat while they are operational and require some cooling. Normally cooling is done by adding a  passive cooling block, thought fans may also be used.

Rectifiers need to be matched for the application based  on their voltage and maximum current.

The rectification losses are not large when compared to the reverse of the process; inversion.