I'm trying to figure out what kind of inverter I would need to run an air compressor that needs a dedicated 15 amps? 750 watt continous inverter? More?

 

P=IV
P=15A x 110V=1650W continuous

Of course if you're pulling 1650W on the 110V side, you're pulling the same amount on the 12V side too. So...

P=IV
1650W=I x 12V
I=137.5A

You'll be pulling 137.5A from the battery. But then, there are losses from inefficiencies in the inverter so add about 10% to the numbers. In short, it won't work for a stock electrical system and inverters over 1000W continuous are really expensive.

 

Get a big rig...

hehe, seriously though, I don't think a light truck/car will cut it. Maybe you can find a dedicated compressor for vehicles that will do what you want?

 

First a primer on electrical terms ... to compare it to water over a mill wheel volts is the amount of water, amps is how fast that amount is moving and watts is how much work (wheel revs) it is doing.
You say it needs 15 amps continious (at 120 volts you would need an 1800 Watt inverter to RUN it. You need to look ( in the manual or on the motor name plate) and find out what the starting or" in rush " current (amp) requirement is (this is the amount of power needed to start the compresser) this is always higher then the running amp requirement. They may have already inluded this in that 15A requirement but you should check.
That 1800W figure is the minimum number, you should probably go for a 2400W inverter to give yourself a little room (you might need to run a light or something else at the same time) . If you go for an inverter try to get a marine type it will typically be more corrosion resistant and have a GFI (Ground fault circuit interupter) recepticle (wall plug) on it. GFIs are safer for plugs that are outside or that maybe used in the wet, they can save you from being electrocuted if you drop the tool / light / etc. in a puddle. Hope this helps sorry 'bout the long post Aviator

 

robinhood is right you would need to step up the alternater too... Linkarc makes a 200A alternater for car/truck use as part of a mobile welder kit. It is available seperately but I don't know the price. Check with a local alternater rebuilder they usually have or can fabricate a high output alt. for you. Just remeber to upgrade your alt-batt. harness to handle the heavier load.

 

It would take a LARGE inverter to start a 120V compressor. On our jobsites we will run a small compressor/circular saw off a 5000W generator before there is temp power. The generator will strain for a second when the compressor or saw starts. This can be hard on equipment and make it run hot.

 

quite right, typically, the startup current is a very large spike that is many times the running current. heres an idea, why not use the engine for an air compressor?---hint... the a/c pump is very efficient and can charge a 15gal air tank to 200psi in under 20 seconds.

T

 

Wow, thanks for the great responses guy. I was looking at a small air compressor that Sears had for $99 as an alternative to on board air. I guess I'll have to look elsewhere. Thanks again.

 

I deleted my original response because it seemed that I was wrong, and I have no idea why I was wrong.

Anyway, why not look into a 12v compressor? You'd do away with the need for an inverter. I have a TruckAir. It's not the fastest, but it is good enough for once in a while

 

Either get one that uses a DC motor or better yet run the compressor off the engine with a belt.
It is VERY inefficient to turn mechanical energy into DC then into AC finally back into mechanical again!
The guys are right, the start-up spike will kill the inverter.

 

Well, you used the right equation, but the invertor you linked to was 1600W peak, not continuous power usage. It was rated for 800W continous but the equations show the compressor will draw 1500W continous. The PEAK rating is so that it can handle that power spike when the electric motor in the compressor is starting up.