Portable 12 volt air compressors?

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psytechguy

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I know some of ya'll have gotta be using these. What's a good one?

I'm looking for something a little more high end than the cheap "tire inflators" you typically see for sale at Home Depot, Pep Boys, etc.

thanks!
Mike
 
What are you planning to use it for?
 
I used a 120v 3 gallon compressor for a few years until I shut off the generator before shutting off the compressor, the compressor never worked again after that. Then I had a craftsmen rechargeable tire inflator, this worked great for tires that were low on air. But died when someone used it to inflate a flat tire, tire inflators need to be shut off and cool down after few minutes or they will over heat. Now I have a inflator made by Slime I bought at Walmart, I have only used it once to top off some tires that were a little low and it worked good. I have found some high end tire inflators on JC Whitney site for about $100-200, these are used by off road people they reduce their air pressure for off road traction then inflate the tires for pavement. And these high end inflators are usually wired into the vehicle electrical system or auxiliary battery.  
 
I just recently changed out my viair electric compressor,  for a York engine driven compressor.  what a world of difference.  the viair is considered top of the line but I still found it lacking.  it was faster than the cheap ones but still slow.  viair also states that their compressors should be run at 14v so basically you have to have your engine running anyways.   so I put the York on and boy that sucker puts out air.  btw the viair is for sale.  highdesertranger
 
I've got a masterflow MV-50 I've been happy enough with, but not so happy that I left it stock.<br><a href="http://www.amazon.com/dp/B000BM8RT8...vqmt=b&amp;hvdev=c&amp;ref=pd_sl_8hk37onbv5_b" rel="nofollow" target="_blank">http://www.amazon.com/dp/B000BM8RT8...vqmt=b&amp;hvdev=c&amp;ref=pd_sl_8hk37onbv5_b<br><br>I</a>t hooks directly to the battery with alligator clips, as it draws 16 to 18 amps, more than any ciggy plug outlet can handle.<br><br>Viair units were the mac daddy of 12v compressors, but then their production moved to china, just like everything else. &nbsp;I think they are still better built than the linked product though. &nbsp;The old Made in the USA viair are still the gold standard, if you can acquire one<br><br>I have modified mine, retapping the head for standard air fittings, and adding a 80mm fan to blow over the head. &nbsp;If seriously interested in these modifications, I got pics, and some safety recommendations.<br><br>Lots of clones of this basic compressor are out there. &nbsp;I think mine says 13.7 volts is maximum, and some guys on jeep forums with oversized tires have ruined them by running the engine at 14.5 volts when re inflating 4 large tires. &nbsp;I don;t think the supplied wiring could still provide &nbsp;much over 13.7 at 16 amps. &nbsp;I think they died from overheating, as it says 30 minutes max run time, and re inflating 4 big tires can exceed this.<br><br><br>
 
I also had an MV-50, and it was great for putting a few pounds of air into low tires, but it bit the dust when I tried to air up a flat on my F-150.

Still have it, it looks brand new, so I haven't had the heart to trash it. Blew it's fuse and never recovered. Maybe I just got a bad one.
 
The mv-50 is simple to repair. &nbsp;They are known to blow &nbsp;their fuse but usually only when starting them on when already attached to a pressurized tire. &nbsp;Trick is to turn it on, then attach it to the tire.<br><br>The reed valves inside are also easy to replace. &nbsp;Many have done so but cutting up a tin can to remake the valve. &nbsp;If it makes noise but does not fill the tire, bingo.<br>
headplatebottom_zpsc9212dd0.jpg
<br><br>The arrow is pointing to a piece of plastic which got sucked into mine the one time I did not use the filter. &nbsp;The unit still worked with it obstructing the airflow, it was just slower.<br><br>There is also a standard &nbsp;Bosch style 30 amp relay inside than can go bad. &nbsp;Cost under 5$ to replace, plug and play. &nbsp;If the fuse has been replaced but the unit will not turn on, the relay or its connections are &nbsp;highly suspect.<br><a href="http://www.amazon.com/Absolute-RLS125-12-VCD-Automotive-Relay/dp/B0002KR9GG/ref=pd_sim_sbs_e_1" rel="nofollow" target="_blank">http://www.amazon.com/Absolute-RLS125-12-VCD-Automotive-Relay/dp/B0002KR9GG/ref=pd_sim_sbs_e_1<br><br><br></a>
 
Thanks, I'll check it out!

I'm gonna feel kinda foolish if it cranks right up with the compressor unattached to a tire. :)

I'd be interested in seeing your mods. Being able to use a standard air fitting would be nice.

Mike
 
Well, I went out to the shop and drug this thing out of the corner it'd been sitting in for the past 2 years. Hooked it up unattached to a tire, and no go.

Looked at the fuse, it was good. Got out my meter and double checked the fuse, it was still good. :)

Got to checking out the cheap little fuse holder and discovered that the connection was broken on one of the spade lugs that the fuse plugs into. DOH!

Fires up like a champ now. I need to wire in a decent fuse holder. This one's about as cheap as they could make it and still have it hold a fuse.

So, I'm not feeling totally foolish. I'm just glad to not have to buy another one!
BTW, mines an MV-1050 "Tsunami." Looks pretty much just like your MV-50.

Thanks for your post. It prodded me into looking at the problem again and fixing this thing!
 
Glad it was an easy fix. The mv50 and MF-1050 are the same product with different price tags<br><br>They are built cheaply, but luckily it is such a simple device they cannot screw up too much. &nbsp;Here is one of their internal wire nuts. &nbsp;Not a screw type, but one which crushes a lug inside the "nut"<br>Mine pulled apart with little torque on it.<br>
cheezycrimps_zps24576172.jpg
<br><br>It was these wire nuts holding the wire inside the &nbsp;end cap. &nbsp;There was no real cord grip or strain relief, just a hole in the plastic with the wire going through it, which is just horrible.<br>
plasticback_zps37af4c40.jpg
<br>Here is the inside of the endcap, showing the relay(blue) so the full current does not have to run through the little toggle switch.<br>
relayandswitch_zpsfeef62c9.jpg
<br><br>I drilled the hole bigger and added some &nbsp;standard strain relief so I could swing the unit around like a weapon from the cord.<br>
strainrelief_zps56160738.jpg
<br><br><br>My main complaint with the function of the unit is the tire valve(schrader valve) adapter, which must be threaded on, and has this weird deflating function as well, which operated when not asked to if in a certain position.<br><br>The head is tapped for some metric fitting, and probably the easiest thing to do is get an adapter. <br>Here is a standard 1/4 NPT fitting on left, and the provided one on the right.<br>
standardairfittingsandstockmv1050_zps85bb022c.jpg
<br><br><br>Here is &nbsp;why you should use the provided air filter:<br>&nbsp;
cylinder_zpsa5cf523a.jpg
<br>Here is the leather cup on the piston, and the cylinder sleeve.<br>
piston_zpsebb5f62b.jpg
<br>I cleaned the crud off it and lubed it with some Syl-Glide.<br>
pistoninbore_zpscc613754.jpg
<br>
headplatewithchecvalves_zpse824dabe.jpg
<br>
head1050_zps66302e4a.jpg
<br><br>Make sure to remove all the plastic flashing left over from the molding &nbsp;on the filter housing process so as to not restrict airflow into the unit. &nbsp; This can easily restrict performance and overheat the thing. &nbsp;Mine was very restrictive. The filter in place quietens the unit considerably. &nbsp;Sorry no Pic.<br><br>1/4 npt taps are cheap. &nbsp;I ordered one on Amazon for 4$, and received 4 of them. &nbsp;The head comes off easily with 4 allen head bolts which were likely not tightened enough anyway. &nbsp;There is no need to run a drill through the head beforehand, but I did. There was almost no resistance to the drill bit. &nbsp;i could have done it with my fingers rather than on my drill. I forget which drill size I used. Just go slow backing off frequently, use some oil, and do not go too far with the tap as it will bottom out within the head and could crack it.<br>
tapinsidehead_zpsadf58e4b.jpg
<br><br>
retaphead1_zps1a26c088.jpg
<br>Don't forget to wear OSHA approved footwear.<br>
oshaapprovedfootwear_zpsb3d433b8.jpg
<br><br>Make sure to clean the metal shavings<br>
onequarternpttappedhead_zps5d88df5f.jpg
<br><br>I ultimately chose not to use any of the quick release standard fittings as I never disassemble mine to return it to the provided bag.. &nbsp;I had acquired a new &nbsp;coiled airline and attached this directly to the head.<br>
newhosedirectfit_zpseb29a443.jpg
<br><br>One reason I did not want to use the standard air fittings is they are not passive, like the fittings which came with the unit. &nbsp;If one were to turn on the unit with standard fittings, pressure would quickly build(within 2 seconds) past 150 PSI and blow out something, possibly dangerously. This was not how it ended up:<br>
mv1050beforemuffinfan_zps13349b86.jpg
<br><br>I used a locking tire chuck, but I disassembled it so that I could drill a small hole through the part which depresses the shrader valve needle. &nbsp;Now the pressure cannot build up, and it is mostly idiot proof.<br><br>
modifyairchucktofreeflow_zpsf6cd0cb2.jpg
<br><br>Backtracking slightly, these units get hot. &nbsp;Most of that heat is generated by the piston moving in the cylinder. &nbsp;The cylinder head is designed as a heatsink, but the head does not fit tightly over the cylinder sleeve. &nbsp;There are 4 contact points which hold the sleeve in place within the head, and these are the main heat transfer points. &nbsp;Not very much surface area to transfer the heat. &nbsp;Here you can see the contact points, and the 1mm air gap. &nbsp;I filled this gap with a high temp grease to better transfer the &nbsp;cylinder sleeve heat to the heatsink.<br>
airgapandcontactpatch_zpsc6bac6b7.jpg
<br><br>To further assist in heat removal, i wired up a 80mm computer fan also activated by the relay.<br>
fanmountfromback_zps64c1bb3f.jpg
<br><br>You can also see my added cord grip, and the thin wires exiting to power the fan.<br><br>Here is where my compressor resides. &nbsp;It is powered by my main fuse panel, and retains its original fuse as well. &nbsp;NO quick release fittings, and I added a couple unnecessary extensions to the locking coupler just for ease of use.<br>
popthehatch_zps1748ada8.jpg
<br><br>The unit resides in one of my hatches located over the wheel hump. &nbsp;In the compartment next to it is the valves for my rear suspension helper airbags, and my water tank. &nbsp;My water pump cannot self prime, and I pressurize the tank with the compressor to prime it.<br>
pumpingpsairbag_zps74e393ac.jpg
<br><br>I left the power cord long enough to rest the unit on the ground outside my side doors. &nbsp;It also has a quick connector on the wire so I can plug it back into the provided alligator clips, or various power points located elsewhere in my van.<br><br>So you see, this unit is capable when new out of the box, but with some refinements can be turned into a reliable, much improved, easy to use compressor, if you apply some time and skills to make it so.<br><br>I think with the added grease between cylinder and heat sink, in addition to the 80mm computer fan, there is no longer any 30 minute maximum runtime. &nbsp;Before the upgrades the heat sink would get so hot as to be uncomfortable to touch after 5 minutes of running. &nbsp;No longer.<br><br>All of this type of compressor and the Viair clones are likely very similar inside as the design is so simple. &nbsp;Harbor freight has a couple versions of various size that get pretty good reviews, but I would upgrade/fine tune them as well before depending on them in a situation where failure could leave you stranded.<br><br><br><br><br><br><br><br><br>
 
wow nice write up.&nbsp; excellent pics.&nbsp; very informative.&nbsp; highdesertranger
 
Excellent instructional!<br><br>What sort of high heat grease did you use for the heat sink?
 
I just used Hi temp Wheel bearing grease. &nbsp;Not ideal I know, but none has degelled and made a mess, yet. &nbsp;If you have any mechanical skills, these are incredibly easy to take apart and return to operational. &nbsp;If you have ever run one without the airfilter, I recommend cleaning it of debris.<br><br> &nbsp;I have used it on a couple low load range E tires(not mine) taking them from 32 to 80psi since my Mods, so it had plenty of chance to get plenty hot and allow the grease to flow.<br><br>Mostly mine gets used for priming the waterpump and air bag adjustment, as my newish tires lose very little if any air. &nbsp;Takes about 30 seconds to pump an airbag from 5 to 100 psi, not long enough to generate much heat. &nbsp;Priming the water pump by pressurizing the tank requires turning it off after about a second. &nbsp; It barely registers any PSI on the gauge before the water pump changes tone and water shoots from the faucet.<br><br>I could just imagine rupturing the tank with 7 gallons in it. &nbsp;<br><br><br>
 
$10 tire inflator from Trak Auto haven't broke yet. Trak Auto went out of business over 15 years ago too. Used it to inflate completely flat tires before, and many times. Compressor was so hot, I couldn't touch it. 2nd one for $15 in a Slime package with a bottle of Slime included didn't break yet neither. You guys must be doing really heavy duty inflating...mine's just for emergency.
 
Now that I've got mine running again I've done the following:

Replaced the cable with heavier gauge wire.

Replaced the fuse holder with a better one.

Did the grease/heat sink mod.

Looked at the air cleaner and it was 50% restricted from plastic mold flash. Cleaned that out. What a difference in the way it runs!

Thanks again for the suggestions and tutorial!
 
Sweet.<br><br>Amazing how much mold flash was left over on the filter housing on mine.<br><br>The heavier gauge wire has to help too. &nbsp;I never measured the voltage drop on mine, but when I plug it into the connector closest to my batteries over the fattest wire, it seems to have more Ommph.<br><br>I'm considering adding a reservoir tank. &nbsp;If I find a nice one from a worn out compressor that will fit underneath cleanly, I'll definitely plumb one up.
 
&nbsp;For thermal transfer, you might want to look into some Arctic Silver thermal paste which is used on CPU's to transfer heat from the chip to the heat sink.<br><br>&nbsp;As for hand pumps... good luck pumping up a 16" LT tire running at 85 PSI; can be done, but a truly masochistic endeavor.&nbsp; ..Willy.
 

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