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Ryobi P739 18 Volt Compressor Is Very Handy And Is Holding Up Great!

The one thing I notice about getting older is that I don’t have the strength to go lugging around as much as I used to not to mention I don’t have a ton of patience either.  This issue affects me when it comes to portable compressors.

Because of Ronin’s Grips, I have a big stationary 60 gallon Ingersoll Rand compressor.  To work on cars, I run 50-100 feet of 3/8″ air hose to where I am working and life is great,  For years I had a portable two gallon compressor that required AC that I sold because it weighed quite a bit and needed an electrical cord.

Last Spring, I started hearing about various tool companies making cordless air compressors that could be used to run nailers, staplers or even inflate tires.  That idea definitely caught my attention.

I then read about the Ryobi P739 1 gallon air compressor that uses their common 18 volt batteries.  I have a ton of Ryobi tools and batteries so I bought one from www.homedepot.com with home delivery.  Note, I specifically bought the model above – there are other previous models but I can’t speak to them.  Also, the website will frequently sell different bundles (the unit with a charger and at least one battery) that you will probably not see in a store so at least check the website before you buy.

First off, this is not an inflator that puts out tiny amounts of air.  This has a 1 gallon tank that is pressurized to 120 PSI and has an adjustable regulator.

This little compressor is meant for tools that have low air requirements or inflation as it does not put out a ton of air – 0.75 standard cubic feet per minute (SCFM) at 40 PSI or 0.5 SCFM at 90 PSI.  Note, I am just going to write SCFM for the compressor because Ryobi says the above is a SCFM rating.  CFM is different and click here if you want a pretty good explanation.

Once the tank is pressurized, you’ll have enough air to run a brad nailer, finish nailer or stapler.  The question becomes how many nails can you drive before the compressor will need to kick on and refill the tank.  The answer unfortunately is “it depends” because of the requirements of the tool.  It will never put out enough air for tools that require a lot of air like ratchets, impact hammers, sanders, spray painters, etc.  Don’t even consider it for those tools that say they require over 2 CFM.  The Ryobi simply was not designed for those use cases and never claimed to be.

This little compressor will probably be great for 10-20 finish nails/staples and then need to run its compressor.  If you try to use the tool too fast when it is trying to recharge the tank, odds are you will draw more air than the tool can deliver and the pressure will continue to drop.  Remember – the compressor itself is small.  When the tank pressure drops and the compressor kicks on, it will need time to recover.

You’ll notice I didn’t mention a framing nailer or even a roofing nailer.  Odds are the compressor can do a few of those but it would never keep up.  Portable job site compressors for nailers can deliver 3-5 SCFM @ 90PSI and keep up with even several nailers running.  If you plan on some quick fix with just a few nails then sure, this would work.

What this little Ryobi brings to the table is portability.  It is only about 14 pounds before you add the battery and tools.  I use one of the big 4 amp hour Lithium Ion batteries on it and then keep a 25 foot Amflo line on it with Milton 1/4″ quick connect fittings.

I like the Amflo line as it is made from polyurethane and remains flexible even in cold weather plus it doesn’t leave scuff marks everywhere.  The old rubber and PVC air hoses are big, bulky and really get stiff. The challenge is keeping all the Amflo hose on the unit when moving it around. Velcro really helps. I started with an oddball strap that I had laying around. It helped but I needed two more to really secure it and used a cool double sided “Velcro” tape that is out now.

I use a hook and loop tape that rocks.  The brand name you know is “Velcro” but you will hear people generically refer to it as hook and loop.  At any rate, this stuff has the hook one one side and the loop on the other – you cut off the roll whatever length you need and it is simply fantastic for managing cables, or in this case, keeping that Amflo hose on the holder.  I use three pieces – on the two sides and one at the top – because most of the time I am using just a short section for topping off tires.

As mentioned in the past, I just use Milton fittings now.  Harbor Freight, Home Depot and other discount brands have let me down one too many times including excessive air leaks with wear and even breaking.

One last small tip, use good Teflon tape.  The stuff I am using right now is off Amazon and is way thicker than the cheapo stuff you often see.

I have a 16ga NuMax finish nailer and an 18ga Wen finish nailer that work just fine with this plus a Surebonder T-50 Stapler.  I have others but these are the ones that I have used with the Ryobi and am happy.  Again, I am not doing high volumes – more like small projects, repairs, etc.

It Rocks For Topping Off Tires

What I use the Ryobi for the most is to top off car and truck tires.  It really makes this chore easy.  Sure my big compressor is faster but to go around and add up to 5-10 PSI to a tire is easy with this.  To give you an idea of size, the next photo shows the unit next to one of my Landcruiser’s good sized 275/70R16 tires.

I used to lug around a portable five gallon tank but it weighs a ton, is cumbersome and I might need to refill it several times before I get done.  If I didn’t do that, I would have to pull the car around by my shop, hook up a line to reach it and then fill the tire – that can also be a headache unless the line is already hooked up.

What you see above is a Milton S-506 tire inflator that I keep on it.  I have another in the garage that is beat to death but still working.  It is so very, very handy to have the inflator and pressure gauge in one unit plus chuck heads at two angles for bikes, tractors, trailers, etc.

To give you an idea, I recently had to add about 2-4 PSI on each tire of my daughter’s 2002 Camry to get them up to 40 PSI.  The regulator was set at 90 PSI and it had a freshly charged battery,

Part way into the first tire the compressor turned on and continued running as I did all four tires on the car.  The battery’s LED charge indicator dropped one bar out of four.  The compressor turned off maybe two minutes after I topped off the last tire.

In summary, I’ve been using this compressor for over two months mainly for topping off tires and that really puts some stress on the little unit.  It seems to be holding up just fine.  It gets lugged around my shop, the drive way in the trunks of cars and no problems.  I can easily go out and check all our vehicle tires and top them off where they sit .

If you use Ryobi 18 volt tools, have the batteries and are in the market for a light duty portable compressor for the uses I outlined above, I’d recommend this one.  If you use another brand of 18-20 volt tool, I bet your vendor is making a portable compressor as well that you might want to research.

5/21/2019 Update:  This thing has been awesome.  I use it at least once a week to top off tires and has been great.  I’ve also used it a few times to run staplers and a finish nailer.  I really like it.  It definitely uses quite a bit of power so if you plan on using it a fair amount, I’d recommend at least 4.0Ah, or even better the new 9.0Ah, batteries you will be using the unit extensively.  I always have several batteries with me too.


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Tired of tripping your circuit breaker when your air compressor refills? You can easily fix that!

I tell you what it is really hard to get by without a compressor but it can also be but it can also be a real headache if the circuit breaker regularly, or even unpredictably, trips when the compressor tries to top off the tank.  There a couple of really easy modifications we can do to the compressor but before that, let’s step through a couple of things first just in case there is another issue at hand:

Safety Stuff

I actually spent more time trying to think about the what-ifs than actually writing the two options to make your compressor start softer but I do want you to approach this safely.  I am assuming you are handy with a basic understanding of electrical wiring and compressed air to do this work.

First, you should be using a properly sized circuit or at least one that is very close.  If your compressor needs far more than what your circuit is sized for, say 30 amps and you only have a 15 amp circuit, then the fix I am going to tell you may not help.  It  does often help when you have a circuit that is very close to the required amps but when there is a heavy draw, it exceeds the circuits capacity so the breaker trips.  My experience is that consumer air compressors list a low draw number like 15 amps and can draw more than that under peak load.  So, for example, if you have a 15 amp circuit and a compressor that says it needs 15 amps – you may be having some challenges that this modification might help with.

In terms of properly sizing a circuit, engineers and others can give you rules of thumb such as doubling the circuit capacity to allow for spikes in demand or to allow 6 amps per 1 HP for 1 phase or 1.25 amps per HP for 3 phase.  Doing this means running new wire and installing new breakers.  DO NOT JUST PUT IN A BIGGER BREAKER!  The breaker is protecting the wiring from over heating and catching fire.  Each thickness, or gauge, of wire has a limit to the number of amps it can carry.  Never put a higher capacity breaker on a smaller cable – you are asking for trouble in the worst way.

Second, plug the compressor directly into the wall.  An extension cord will likely introduce too much resistance and cause the breaker to trip so do not use an extension cord (assuming your compressor is not an air nailer or air brush model – they draw so little that they can use extension cords).

Third, I have only encountered this a few times over the years but breakers can wear out over time.  If you investigate and it seems that you should have enough capacity and can’t figure out why your breaker is tripping, then try installing a new breaker and see if that helps.  Again, install the right size and don’t put the wiring at risk of fire.  If in doubt, bring in an electrician to straighten things out.

Fourth, if you look at your outlets and/or wiring and they look burned, there is any trace of soot or a burned smell stop and get an electrician to inspect the line.  It may sound funny but I have seen lines fail over the years for a ton of unexpected reasons.

Now, on to making a compressor softer starting

So, with those things said, let’s say you need to make your compressor work better with the circuit you have for whatever reason, let’s talk about what some folks call a “soft start” modification.  It’s called this because it makes it easier for the pump and compressor to start and come up to speed before a heavy load is introduced.

The way a compressor works is that a motor has to turn the pump and send air through a filler tube into the main tank. Between that little tube and the tank is a check valve that screws in right at the top of the tank that keeps air from rushing backwards. Now when the compressor fills the tank each time, the switch controller opens a bleed off valve to empty the air in the filler tube to make it easier for the compressor to start next time.  The problem is that the volume of air in that tube is relatively small and when your compressor starts, it can only turn a few times before the tube is full and then the motor must work much harder and thus draw more amps to overcome the check valve to put air in the tank. Depending on the amps required, this can then trip the breaker.

Look at this next photo. See how short and small that left tube is?  The pump can only turn a few times before that left tube is pressurized – it never has a chance to build up speed and momentum in the flywheel. As a result when the pressure of the tank is reached it puts a lot of strain on the motor.

Note, the second smaller tube, which is often a flexible plastic, provides pressure to the cut off switch that automatically turns the motor off when the tank reaches a specified pressure.  We are interested in the larger tube that runs from the head (top) of the compressor pump down to the top of the tank.  It is usually much larger than the pressure switch tube.

The fix is simple – increase the air capacity between the pump and the tank!  You want the motor to be able to start and the heavy flywheel build up momentum before it encounters the pressure behind the check valve.

Option one:  Simply make a longer tube so there is more potential volume to fill

There are two options to make this softer starting. One is to just add a long length of copper tubing in between the compressor and the tank. You roll it into a coil and it kind of looks like a moonshine still and it does the job. The con is that it looks really funky. I did this with one of my early compressors and the photo below shows about 8 to 10 foot of tubing installed. I would replace whatever the original tubing was with the same size so you would do the same. You need to replace the compression fittings also and you can do the job in about 30 minutes.  Note that I used hose clamps to keep the coils from rattling.  Ugly as heck but it worked until I finally wore out the pump.  I checked the date on my photos and I ran this setup from 2010 to 2014 – it does hold up.

Option two:  Add a reservoir to really increase the volume

The second approach is a little bit more elaborate and involves putting a 1/2 to 1 gallon small air tank between the compressor and the tank. This allows the pump and motor to come up to speed before they must overcome the check valve. This works great. The only slightly annoying thing you will notice is that once the pressure is reached and the compressor cuts off, the pressure relief valve opens and the air runs out longer because there is more air in the line.

A couple of quick design considerations:

  1.  I carefully bent the aluminum using a tubing bender and tried to avoid abrupt turns.
  2. The small tank you see is a Firestone 9125 1 gallon 150 PSI tank.  The compressor filled the main tank to 135 PSI so the tank needed at least that rating to be safe.  Be sure your tank is at least rated as high as your compressor.
  3. Factor in the length of tank and if you will have enough room.  The one pictured is 12″ long.
  4. The tubing should be at least the same diameter as the original and the tank’s fittings should be adequately sized.  This is a fairly small compressor in the photo.
  5. I secured the tank to plywood and the plywood to the original compressor using the screw hanger fittings you find with conduit.  I wanted it to be relatively portable and I also wanted the wood to take up some of the vibration.
  6. I installed a T-fitting at the bottom of the tank to drain off moisture and never really found any.  I would recommend you still add it even if it just gives you an ability to bleed off air if something happens.
  7. Use quality Teflon/PTFE tape on all of your fittings to prevent leaks
  8. An optional recommendation I would urge you to do is to either use brake-line wrenches or at least quality fixed wrenches to avoid rounding over the fittings.  It is easy for an adjustable wrench to slip and round over the edge of a fitting.  You need to tighten things firmly so they do not leak or come loose.

I got by with the above for a number of years until I could afford to both get a bigger compressor and pay an electrician to run a 240 volt service into my shop.  I don’t need it now but these two approaches got me buy for almost six years.

IMPORTANT SAFETY ANNOUNCEMENT – BE SURE YOUR SYSTEM IS FULLY DRAINED AND THE COMPRESSOR IS UNPLUGGED (ENSURING THERE IS NO WAY IT CAN TURN ON) BEFORE YOU DO ANY WORK.  The pressures involved can hurt you and we do not want that.

The last safety comment – if you are not comfortable with wiring and checking things out safely – bring in an electrician. I can’t stress that enough either.


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