So you're looking for information on a 12 volt air compressor? Probably you want to use it in your car to inflate your tires.. I bought one about two years ago exactly for that job. I still use it every now and then to inflate my tires.

I must say that inflating my tires at the gas station is easier and faster. But having a portable 12 volt air compressor with you gives some extra peace of mind. Plus it can come in handy when you go camping for example.

Portable air compressor uses

But inflating car tires is not the only use of a 12 volt air compressor. It can basically used for anything that needs compressed air.

If you have pneumatic tools like a nailer that require compressed air to function, and you want to use it in a remote location, a 12 volt air compressor is the way to go. Just hook it up to your cars battery and you have compressed air whenever you like.

Not for everything

But a portable compressor can't be used for everything. While almost all portable air compressors are capable of compressing air to 7 bar (100 psi) or more, the flow isn't very high.

That's an important distinction to make, especially when it comes to using big air tools on a small 12 volt air compressor.

The maximum pressure of the compressor might be sufficient for the air tool (which normally require about 6 bar to function). But, the air maximum flow is just as important. The maximum air flow is the amount of air (in liters per minute) that the compressor can produce.

If you have a big air tool, like a grinder or air-motor, you will need a lot of air, not just pressure. If the air consumption is higher than the air production, the pressure will drop. When the pressure drops too much, the air tools stops working.

Also stuff like inflating a mattress or an inflatable swimming pool is almost impossible to do with a small 12 volt air compressor. Why? These kind of things require low pressure, but high air flow, while your compressor gives high pressure with low air flow.

Choosing a 12 volt portable air compressor

There are many different types of these small compressors. They range from $10 to more than $1500 ! Of course, what you pay is what you get. Figure out for yourself what is important for you. Here's a list a things to think about:

• Noise: cheap compressors without isolation will make a lot of noise. Even those small ones! If you want to inflate your tires in a residential area, on Sunday morning... you better go to the nearest gas-station (if you like your neighbors ;)
• Maximum pressure. Most small compressors can go up to 7 bars (100 psi), which is more than enough for car or SUV tires, but might not be enough for big truck tires. The tires on my 1996 Toyoto Corolla require 2.6 bar for example.
• Maximum air flow. Don't expect to much when it comes to air flow. 12 volt air compressors are generally small, so the amount of air they can supply per second or minutes is small too. This isn't really an issue most of the time. It will just take a little longer to inflate your tire.
• Shape and size. I bough a $50 air compressor 2 years ago that was round. It fitted exactly in the inside of my spare tire (that was designed that way on purpose of course).
• Electrical connection: low-power compressors will come with a connector that you can plug straight into the cigarette lighter. The bigger 12 volt compressors will come without a plug, but with two clamps that you can hook up directly to the cars battery.

Another point to keep in mind is the duty cycle. Most small compressors have a maximum duty cycle, that is the time it can run, compared to the time it needs to 'rest'. For inflating tires, this is not an issue, as you might just use it for 2 minutes at a time. But if you want to use air tools or anything else that requires more air, be careful not to overheat the compressor by running it too long at a time.

Advice

My personal experience with these kind of small portable air compressors is that you get what you pay for, but you don't need to buy the very expensive ones.

I once bought a very small one for $10. When I tried to use it after 6 months, nothing happened, but I could smell the melting isolation on the power cord! $10 wasted :)

I bought a new compressor, for around $50. It was good, was round so it could fit in my spare tire and it had a build-in digital pressure-gauge that could be taken off to check the tire pressure easily.. it even had a built-in light to make it easier when working in the dark. It still works perfectly now, 2,5 years later.

Bottom-line: make up your mind about what you want to use the compressor for and think about the things in the list above. Skip the $10 ones as they are crap, but if you only use it occasionally, there's no need to go over $50.