Recc For a Little Tire Inflator That Works

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It's simple math. As voltage drops, current will increase if the load remains constant. For example, a 200 watt load at 13.8 volts is 14.5 amps. The same load at 12.5 volts is 16 amps. Voltage drop due to a long or undersized power cord will make the problem worse.
 
My tire inflator recommended you start the engine and run it while using the cigarette adapter.

Since my starter battery is hooked up to charging now, I didn't bother to start the engine.

My rig drove much nicer after I topped up the tires.
 
Many inexpensive "inflators" can add a few psi to a tire - it doesn't take all that long even if the air volume (SCFM) of the compressor is low.  Just need adequate 12v power, as others have described. As previously recommended, a direct connection to the battery is better than trying to use a cigar lighter outlet in the car or RV.

It's hard to find a heavy duty clip lead extension. The best I could locate with a brief search is this 16 gauge model found on Amazon.  16 gauge will handle about 13 amps and probably more if the compressor doesn't run too long, say less than 15 minutes.

https://www.amazon.com/CUZEC-Extension-Battery-Cigarette-Lighter/dp/B071X4HF9K/ref=pd_cp_60_2
And here is an additional extension if needed:
https://www.amazon.com/EPAuto-Extension-Cigarette-Lighter-Socket/dp/B014TZVXH0/ref=pd_lpo_vtph_60_bs_t_1

I haven't used this compressor found on Amazon, but the specs seem decent and the reviews are good.

https://www.amazon.com/EPAuto-Portable-Compressor-Digital-Inflator/dp/B01L9WSTEG/ref=sm_n_se_dkp_US_pr_sea_0_0
 
HappyWanderer said:
It's simple math. As voltage drops, current will increase if the load remains constant. For example, a 200 watt load at 13.8 volts is 14.5 amps. The same load at 12.5 volts is 16 amps. Voltage drop due to a long or undersized power cord will make the problem worse.
Click to expand...
You mean if the wattage (power) stays constant which it normally does not as voltage drops. But motors are different.

If you drop the voltage across a resistor, the current will drop and so will the power and heat. Everything will drop with the steady load (in ohms) as the voltage lowers. But DC motors break these rules, if I understand this correctly.


-Don-  Yuma, AZ
 
DonTom said:
You mean if the wattage (power) stays constant which it normally does not as voltage drops. But motors are different.

If you drop the voltage across a resistor, the current will drop and so will the power and heat. Everything will drop with the steady load (in ohms) as the voltage lowers. But DC motors break these rules, if I understand this correctly.


-Don-  Yuma, AZ
Click to expand...


Since you have a fleet of electric motors here's a tutorial:  http://www.electricaleasy.com/2014/01/basic-working-of-dc-motor.html

DC motors are actually quite complex compared to a resistor.
 
DonTom said:
You mean if the wattage (power) stays constant which it normally does not as voltage drops. But motors are different.

If you drop the voltage across a resistor, the current will drop and so will the power and heat. Everything will drop with the steady load (in ohms) as the voltage lowers. But DC motors break these rules, if I understand this correctly.


-Don-  Yuma, AZ
Click to expand...

Remember, Don, that impedance and resistance behave differently, and coils (all motors) have mostly impedance. The magnetic fields in motors (or any coil, including baluns and other transformers) have a bit to do with it.
 
Larry N. said:
Remember, Don, that impedance and resistance behave differently, and coils (all motors) have mostly impedance. The magnetic fields in motors (or any coil, including baluns and other transformers) have a bit to do with it.
Click to expand...
I thought we were talking DC motors. The impedance should be the same as the resistance. The term "impedance" should not even be used with pure DC.

By definition "impedance" is the AC resistance at a given frequency. Does not apply to pure DC.

-Don-  Yuma, AZ
 
A DC motor has impedance because it's armature is rotating inside a magnetic field.  The commutator and brushes change the incoming DC into AC that matches the armature's rotation.
 
I got the Husky dual voltage inflator from Home Depot. It can be powered with AC or DC. I've only used the AC side of it so far and it works well. My truck tires require about 70-75 psi for the rears and if I'm adding a few pounds it only takes around 5 minutes or so per tire. I would never try to inflate a flat tire with it, but for maintaining tire pressures it works quite well. The DC cord seems fairly long and has large clips to attach to the vehicle's battery. The AC cord is really short and you really do need an extension cord when using AC. It claims 120 PSI capability and I have no reason to doubt that claim, but I've only used it up to 75 psi. It also comes with attachments for balls, air mattresses, etc...
https://www.homedepot.com/p/Husky-12-Volt-120-Volt-Home-and-Auto-Inflator-HD12120/204260884

 
Lou Schneider said:
...The commutator and brushes change the incoming DC into AC that matches the armature's rotation.
Click to expand...

I respectfully disagree with this statement. It doesn't change DC into AC. It simply uses the properties of magnetism to keep the rotor running.
https://www.youtube.com/watch?v=LAtPHANEfQo

Some DC motors may have their AC inputs rectified to DC current in order to run, but DC motor brushes and commutators don't invert DC to AC to run. Brushes and commutators are merely a way to get the current to the rotating rotor and allow the rotor to continue to rotate. They don't change DC to AC.
 
Hammster said:
I respectfully disagree with this statement. It doesn't change DC into AC. It simply uses the properties of magnetism to keep the rotor running.
https://www.youtube.com/watch?v=LAtPHANEfQo

...
Click to expand...

It doesn't change the INPUT, but AC is Alternating Current, which is what happens AFTER the commutator/brushes. With straight DC into the coils of the motor, "the properties of magnetism" would lock the motor in one position and the motor wouldn't rotate more than enough to find its stable position. That's the reason the commutator is needed with DC input.
 
Hammster said:
I respectfully disagree with this statement. It doesn't change DC into AC. It simply uses the properties of magnetism to keep the rotor running.
Click to expand...

My apologies for oversimplifying the explanation -it's not the first time I've been guilty of that.  ;)

If you look at the current in the rotor, it is indeed being fed Alternating Current as it rotates, with the commutator creating AC by  inverting the polarity of the incoming DC every half revolution.

DonTom said:
I thought we were talking DC motors. The impedance should be the same as the resistance. The term "impedance" should not even be used with pure DC.

By definition "impedance" is the AC resistance at a given frequency. Does not apply to pure DC.
Click to expand...

The rotor coil is an inductor, and the resulting inductive reactance is why a motor's current draw is at maximum with a locked rotor and decreases as the motor picks up speed.  At locked rotor, there is no rotation so the rotor coil is fed with the incoming DC.  This creates zero reactance so the only current limiting is the rotor's DC resistance.

As the rotor gains speed, the increasing frequency of the commutator generated AC increases the inductive reactance of the rotor coil. This increases the total impedence of the motor, reducing the current draw as the RPMs increase.
 
^^^^Finally!, If the above doesn't resolve the discussion, there is no help for the  dissenters.  Lets get back to the OP's quedtion.

Ernie
 
I got a Fini Air Boss at local big box store.  $117.  It runs on 110 AC only, it comes with regular hose and an inflation hose.  My MH has an outside outlet near the back tires on each side of the rig so no worries with the hose reaching the tires.  The pressure runs up to 135 very quickly and it will run an impact wrench just not very long.

"CX"
 
Another very happy Viar owner, not inexpensive as mentioned earlier but what I spent on cheap air compressors before throwing in the towel I could have bought the Viair in the first place and saved a lot of aggravation.
 
Ryobi Inflator

https://www.amazon.com/Ryobi-P737-Portable-Cordless-Inflator/dp/B017JIWT9U/ref=pd_cp_469_1?_encoding=UTF8&pd_rd_i=B017JIWT9U&pd_rd_r=745ZATYWC3MYR9RKS8PM&pd_rd_w=QvNFU&pd_rd_wg=XeGI2&psc=1&refRID=745ZATYWC3MYR9RKS8PM

Very inexpensive ($20 on sale) if you already have Ryobi Tools.  Another $50 if you catch the drill/charger/battery on sale.

I bought one.  Used it to top off the tires for a trip.  Big compressor now lives in the shop for air tools.  Bought two more for wife and daughter.  Entirely too easy.
 
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