THE NEXT MYTH BUSTER
 

Hello and welcome all. I have always been curious to find out how much voltage can a glow plug handle. Well I have a used glow plug which is worn out on the nipple or broke. So I will start with 1.5 volts and move all the way up until I can get it to blow. The batteries I will be using for the test are AA and 9V in series to obtain higher voltages. Hang on your seats for the results.

PS don't tell me to follow the manufacturers recommendations. I would rather ruin a glow plug than a engine in any condition. Told you I was psychic. ;)

RE: THE NEXT MYTH BUSTER
 

I know it isnt 12 volts;)

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Some plugs will take 2V with no problem. It depends on the model.

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It seems it's less than 240 volts...I just plugged one into the house mains. Maybe it'd be OK in America where you only use 120 or something?

JUST KIDDING GUYS!!!!!!!!!!!!!!!!!!!
:D

RE: THE NEXT MYTH BUSTER
 

12 volts :D , Here are the pics of the glow plug and the plug powered with the standard 1.5 volts NiCad battery.

RE: THE NEXT MYTH BUSTER
 

I needed that laugh downunder and gjeffers ................:D

w8ye, I have been past 2V with this particular plug but I will let the experiment tell the details. ;) . Also it depends on the batteries.

RE: THE NEXT MYTH BUSTER
 

OK, the pic below is of the plug at 5.8 volts using 4 AA alkaline batteries . I'm not sure if alkaline is any different from NiCad batteries accept for the AmpHrs.

RE: THE NEXT MYTH BUSTER
 

Curious as to the current capability of the alkalines. They are not of a high current chemistry.
The plug will pull around 2.5 to 3 amps at 1.5 volts.
This means that at 6 volts, it should try to pull around 10 amps depending on how much coil the resistance increases with temperature.
I suspect that you will find that the alkalines cannot produce this much current and the actual voltage at the coil of the plug will be somewhat less than 5.8, thus, not an excessive amount of current.
Let us know if you feel like trying it again using a 6v nicad or maybe an ammeter in the circuit !!!
Or, even a power supply that can deliver the current !!

RE: THE NEXT MYTH BUSTER
 

Thanks OLDCOOT but, I am not concerned to much about the current . I'm trying to discover how much voltage the plug can actually handle . I will do a 9v battery next, if it holds for 5-20 seconds then I will have pleased my needs . I will continue to go up in voltage until the coil fries

RE: THE NEXT MYTH BUSTER
 

I hate to be the one to tell you but....................if it can't supply the current the voltage will be down at the plug. Clip a volt meter on right at the plug and let it tell the tale. When done you might want to waste another plug and try it on a running engine, pull it between runs to see how it looks.

Ed M.

RE: THE NEXT MYTH BUSTER
 

I am generally ignorant of things electrical. However, I always thought that it is the amount of electricity that lights glo-plugs or kills people, not voltage. Electrical quantity is measured in amps not volts. So, in the plug test should not the plug be tested for amperage amount not voltage?

Educate me please.

Ed S

RE: THE NEXT MYTH BUSTER
 

RC-Friend. What we are saying is that if the battery cant supply the current then the glow plug isn't seeing the voltage that you think. E = I x R.
You may be using a 9V battery but the glow plug is only seeing 6V, make sense? So if you are not using volt meter, you still do not know how much voltage the glow plug can handle.


ED. Actually it is neither. Current kills. It is just that you need enough voltage to create enough current to kill or light that plug.
The rason our glow plugs get hot is because there is so much current going through that little filament that it gets hot.
Light bulbs are a good example. The higher the wattage, the lower the resistance. Less resistance means more current and a hotter filament. Hope this helps.

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:eek:

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No....every thing powered by an electric source is rated in volts. DC or AC. I am trying to see if I can surpass the voltage rating for the glow plug and by how much before it burns out or up.

Although this may be true , I have to say any thing drawing current dampens the true voltage reading. I am using pretty much used but in good condition batteries to perform this test. Even if I used new batteries , all I am doing is shorting positive to negative to get the plug to glow.

I was able to connect eight 9 volts in series to have 60 volts. When I connected the plugs positive side ,which truly there isn't any positive or negative because you can reverse the connections and the plug will glow, the tip began to weld to the alligator clip , but the plug still was glowing . I was too tired to go further with more batteries .

So to conclude this MYTH BUSTER , the plug will never burn up instantly , but only over a period of time. Using more voltage will shorten the amount of time the glow plug will last . ;)

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Ni-Cads are rated at 1.2 volts and alkaline at 1.5. But that is a nominal average over the life of the battery. If you use a single C alkaline and a single C nicad you will find that the nicad will glow hotter. If you measure the voltage at the plug you will find about 1.2 volts for the nicad and less than that for the alkaline. This is because the battery voltage is rated for low loads and since the nicad has low internal resistance it will supply more current and voltage.

RE: THE NEXT MYTH BUSTER
 

The batteries you are using are obviously not up to the job!
That glowplug will not tolerate much over 2V... maybe not even 2V at all, since it's a 1.2V plug. The fact that you can hook up such a high voltage to the plug without killing it simply means that the internal resistance of the batteries (combined with the resistance of your leads and clip) makes for such a big voltage drop that the current flow stays below critical.
If you hook up a voltmeter while you are testing that 9V battery, you will see what that means.

Alkaline cells CANNOT deliver these kinds of currents. I once tried 2 big alkaline D-sized cells in series on a plug (3V), and they couldn't even get the plug glowing.

If you really want to test this (I still wonder about what you are trying to achieve here), you need an adjustable regulated power supply (something that can deliver some power, say 10 A), preferably equipped with precision V and A meters, some decent cable that can carry at least 10 A without dropping the voltage (for hooking up the plug), and a good low resistance glowplug clip.

After that, you will only find out the obvious: that a 1.2V glowplug is rated a 1.2V because it will burn out if you use more...!:eek:

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And I have to say that the true voltage reading is the reading UNDER LOAD!

You can hook up 100 alkaline button type cells is series to have 150V theoretically... but since these tiny cells have such a high internal resistance, you cannot draw enough current to make a plug glow. Net result: the voltage drops, and the plug doesn't burn out.
And you think you now have 150V hooked up to your plug... :D

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Its kinda like trying to start a car with a 12 volt system with a 7amp 12 volt starter batttery. isnt gonna happen[sm=spinnyeyes.gif]

RE: THE NEXT MYTH BUSTER
 

RC Fiend - all of the advise you've been given here is true. Understanding electrical theory is critical for undertaking even a simple experiment like yours. Do some research on basic electronic/electrical theory and you'll understand.

RE: THE NEXT MYTH BUSTER
 

The only way you'll be able to measure this effectively, is the actual Wattage (V x A) that the Glow Plug can resist, this will depend on the specific glow plug resistance value in ohms. And the combination of voltage + current. As said on previous replies, if the energy source, in this case, a battery has a low limit on current then the voltage will simply be limited as well, and you won't be able to measure it effectively unless you use both a Voltmeter and an Ampmeter at the same time. Currently i am an electronics hardware engineer, so been doing this for 15 years now. My suggestion is you to get a power supply like this (http://www.extech-direct.com/Power-S...EXT-382207.htm) usually found in university labs or electronic repair shops. Connect the glow plug, set a low limit on the current knob, and start to increase the voltage, the play increasing the current limit, you can see the actual values on the display. For your particular approach, where you want to see the voltage that kills it. you will have to set maximum current limit, and then start to increase the voltage slowly until the plug blows if the current supplied is enough.

Hope it's clear.

Felipe

RE: THE NEXT MYTH BUSTER
 

I'm done with the experiment and am starting to see doubt in my results. Well it's up to you guys if you want to try exactly what I describe to prove me wrong. :)

A 12v/7AmpHr battery will start a small car . A general statement saying it wouldn't is false.

I reported the plug started to weld to the clip, what more evidence does one need to believe you can't burn out a glow plug with only high voltage. Other factor such as carbon build up comes in to play when a plug goes bad. I don't need any meters to tell me the Amps or true voltage if I see sparks when connecting it to the clip because I know the current flowing through the batteries is plenty to get the metals used in the experiment hot enough to weld. :)

The reason I did the experiment was to find out, if I had a 9v battery or something bigger, instead of a Nicd 1.2v battery, would I be able to use it with out causing immediate damage to the plug . The answer is yes.


Thanks for your interest ;).

RE: THE NEXT MYTH BUSTER
 

Simple test for you to try, borrow a 7.2 volt nicad or nimh fully charged battery from somebody. Try your experiment again. Watch the plug light brightly and end up in apuff of smoke before you can get it disconnected. This battery has the capability to put out the amps needed without voltage depression.

Oh, and that must be a RC car the 12V 7ah battery can crank.

Ed M.

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The plug will last , but the fuse for the power supply will blow. If not fuse, then the primary or secondary winding will fry, making this method useless . The plug is simply a conductor when voltage is conneted.

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:D And here I was thinking you were serious all this time, nice to know now it was all a joke.

Ed M.

RE: THE NEXT MYTH BUSTER
 

Every conductor has a resistance such as a glow plug which is a coil. or a winding of wire, it should be ~0.5 ohms. The task of the current limiter is to maintain constant current and protect the power supply, as this is an electronic circuit with transistor regulating it. Even if you make a short circuit on the power supply, the fuse, and transformer won't blow. THat is the definition of current limitng power supply. Just if you are interested how physics work, [X(]