DK45s low voltage at solenoid

[k0ua]

Ah, the old "when is a wire not a wire" thing. When a wire is not a wire is when a wire is a resistor. And resistors oppose the flow of currents.

Here is an example. buy beg borrow or steal a 1000 ohm resistor. Place one end of it on a 12 volt battery. measure with your voltmeter neg to the neg of the battery, and positive to the positive of the battery and note the voltage. Somewhere around 12 volts right? Usually about 12.6 to 12.7 for a charged battery. But now measure the positive thru the 1000 ohm resistor. What will the voltage reading be? Will it be lower? nope still around that 12 volts thru that resistor. Change out that resistor for a 10, 000 ohm resistor, what will be the voltage? Still the same. How much current are we trying to pull thru those resistors? Very Very Very little. The current depends on the internal resistance of the meter itself.

Think about this, could we start our tractors thru that 1000 ohm resistor? No of course not, because we want to pull large amount of current from out battery and those resistors will resist the flow of large currents. So resistors don't seem to resist the voltage, they just resist the current. And when they resist the current, when we actually try to pull some current thru the circuit, we then see a huge voltage drop. This is explained very well by the equation E=IR. This equation was defined by a fella named Ohm. back in the 1700's. And it is called Ohm's law. Yeah, it is not just a good idea, it is the law!

So why do we try to start our tractors thru cables with high resistance? Wires are supposed to be wires right? Yeah, they were engineered to be the proper size, and to have low resistance by the tractor engineers, and they work really really well. Right up to the point they don't work like wires anymore and now they start working like resistors.

Why do they do that? Well it usually has to do with a thing called corrosion. A breakdown of the metallic connections in the wires with the terminals on the ends and sometimes even a total destruction of the metal in the cables by turning this metal into metallic salts. These are compounds that do not conduct currents worth a darn. They start to act just like those resistors we discussed earlier.

Corrosion is caused by exposure to the acid in the batteries themselves and water and oxygen in the air. This is a naturally occurring process that is going on all the time. If we can prevent these elements from getting to our battery terminals/clamps/wires, by liberal coatings of something like a grease we can greatly prolong the life of our battery cables.

As an example to the original poster , If he had coated his cable ends/terminals/battery posts with No-Ox-Id battery grease he would have never had the problem to begin with. His cables would have been as good as they day they were made. I have been telling people about this for years, about how I coat the battery cable ends, the terminals and the posts of the batteries with this grease of every new vehicle I get. I never have problems with corrosion. And I never will. And if you were to follow my example you never will either.

I learned the hard way in the telephony industry with our battery plants what that little jar of grease that was sent with every set of batteries we installed was for! Yep they actually included it. With instructions!.

Well, enough about my pontification of my vast knowledge of battery plants, and the old "ounce of prevention worth a pound of cure" thing. But I would advise you this:. Get a jar of NO-Ox-Id. and coat every battery post, every battery terminal, every battery cable and their crimped on ends, and the surface of the ground on the chassis, and the ground bolt and anything else metallic you want to never rust/rot/corrode and to stay like new. Ring! Ring!. Class is out!

 

[k0ua]

After class work for extra credit.

I would have used the old water hose analogy for understanding voltage, current and resistance. BUT the problem with that is not a lot of people have any understanding of pressure, flow rate, and what restrictions in such a scenario actually do.

Here is an example of an experiment that many people don't understand. Open up your water valve and let the water flow out of your garden hose. Lets say your water pressure is 60psi (this is like the voltage)at you house. A goodly amount of water rushes out of your hose in a given minute as defined by your flow rate (your current) and also defined by the resistance of the garden hose and the plumbing in the house( resistance).

Now turn the valve down down down, until just a drip every minute or two would come out of the water faucet. Just a drippy faucet. Screw on the water hose again, and assume it is still filled with water or this experiment is going to take some time.

Now what is the pressure that this drippy faucet is capable of pressurizing the water hose? Lots less? More? The same? It is the same as it always was. That 60psi. The voltage(pressure) remains the same, even though the water faucet is down to a drop or two a minute.

What is the flow rate? Lots less isn't it. The flow rate is down to nearly nothing (current is nearly zero). Why? Because we have introduced way way way more resistance into the circuit with our water valve almost perfectly but not quite on the seat. Water still flows, because of the seat leakage, water is still capable of the 60 psi of pressure, but the flow rate is near zero. But not quite.

If you don't believe me, put your thumb over the end of that garden hose when it is filled with water, and pull up a chair in a shady spot and wait a while.

Your thumb will have a very very hard time holding back that 60 psi from that drippy faucet after a while. If the hose is not filled, and still has some air in it, the air will compress to 60psi and will rush out if you loosen your thumb on the end of the hose. Air is compressible but water is not.

So the water hose analogy holds true for the electrical analogy too. But like I said, not a lot of folks understand this, and I would not be surprised that some on here would even contest what I told you.

But I sincerely hope some of you learned something today. Even if only one learned something, it is worth it to me. Best Regards, James K0UA

 

[Industrial Toys]

Should one actually coat a connector or battery terminal prior to installation, or assemble them clean and naked, sealing in the connection afterward?

About wire size. I am always unclear about the internal wiring of things. Sure, a range has large conductors going to it and then very skinny wiring internally to the elements. Yes, there is no voltage drop, but how to size that wire appropriately? I always tend to go overboard and make wiring a giant pain.

 

[k0ua]

Should one actually coat a connector or battery terminal prior to installation, or assemble them clean and naked, sealing in the connection afterward?

Coat before. Coat the posts. coat the terminals, coat where the cable insulation meets the terminal. Install terminals and tighten well. Coat the ground connection spot on the tractor (assume it is bright and shiney) and coat the terminal going on it and coat the bolt. Tighten well. Coat after if anything looks uncoated. I have done this for over 30 years now. I have never had a terminal/post/cable corrode or go bad.

I have also used this grease to coat screws I drive into automotive sheet metal to mount antenna trunk lip brackets and to mount brackets on the inside of autos where the screws will go into the transmission hump and stick thru to the space between the hump and the transmission. Essentially outside of the auto and splashed with road salt and water. The screws come out years later the same bright and shiny as the day they went in. I don't know what is in this grease, but it is much thicker than ordinary grease, almost a wax. I don't know if there is any miracle additives, or if it causes cancer. But I haven't died yet, and there are no warning on the jar. I am still on the supplies left over from every installation I ever did. I always filched the rest and took the remains in the jars and tubes home. I am starting to run low as I haven't done a battery installation for almost 2 decades now. The race will be, do I have enough to use for the rest of my life before the "reaper" gets me or do I have to actually buy some. :laughing:

 

[PILOON]

A good old standby was to coat terminals with Vaseline.
It worked then so why not today.
Basically the Vaseline prevented acid fumes from corroding the terminals.
Today they offer specific dedicated products at X times the price.

 

[Fuddy1952]

Don't use Vaseline, use the proper stuff!

A good old standby was to coat terminals with Vaseline.
It worked then so why not today.
Basically the Vaseline prevented acid fumes from corroding the terminals.
Today they offer specific dedicated products at X times the price.

 

[Industrial Toys]

I just put new batteries in my Gator. A friend who goes through a million dollars of batteries a year in mobile inverter systems told me not to coat the terminals before. Assemble and spray after. That's what I did, although I questioned his advice in my own mind. I made a mess of the batteries, cables and boots and in the end have nothing on the mating surfaces.

Now, just to be clear. Are we talking the same thing when it comes to lead posts vs machine screw connections, and battery terminal spray vs some other anti-oxidizing spray? I have several battery specific sprays and a terminal grease from Grote. I don't think the Grote grease has the chemical to counteract the sulfuric acid. I have used those little red and green treated felt washers for years with very good results.

 

[Fuddy1952]

Now if I can chime in, I haven't been a member long, but I'm Gary...retired electronic technician/not much college, just electronics a.a.s., ISCET, automotive and I had my own company until retired 4 years ago.
Lots of great info from two people, James KOUA, and Industrial Toys (who I like what he said on another discussion about crimping AND soldering connectors... which I've said on hamb and got fussed at.
Then heat shrink tubing, I sometimes use 2 or 3 layers.
Water every one can understand. The battery is like a water holding tank, one which is under pressure. Think of it like this...voltage is pressure, current is amount. So water, a high pressure hose is going to be thick wall, reinforced. That's voltage...a spark plug wire. Not much current, so small wire but thick insulation. If you had to connect two plug wires together you may want to use 10 or more pieces of heat shrink tubing...make it thick.
Now high volume water. Which works better to fill a swimming pool, a soda straw or a 4" pipe? A soda straw works...if you can wait a few weeks. So water volume is current. A starter motor draws hundreds of amps, so you want a big fat hose...err wire.
Insulation no big deal, only 12 volts...but you want enough so it won't get damaged. Negative ground, the negative battery wire, sometimes no insulation, big braided wire.
Going overboard on wire size, that's ok. A size bigger...on our drag car with battery in trunk, high compression motor, a + wire 20 feet long? You bet...I want a larger gauge!
Resistance...the longer and smaller the wire, the more resistance it has.
One thing...all meters, analog or digital, have by the design of it series resistance. In general, the more expensive digital meters that may be 11 megohms or more.
That's 11 million ohms! So take, say, my Fluke 87V, ground the neg. black lead, touch + to battery +, it reads, say, 12.87 volts. Now hold + lead end with one hand, touch other hand to battery +...it reads 12.87. That's because your body is a resistor, but not high enough to cause a voltage drop in reading. Now try that with a cheap or an old fashion analog...it may read zero or almost nothing.
I have my Dad's Simpson 230 here I inherited years ago and it's 1000 ohms per volt. At times, with certain tests, both are good...the Simpson actually puts a little load on the circuit.
One thing you can see water...electricity you can't (except lightning or any high voltage arc). So electricity can be mysterious and baffling. Like in automotive class 40++ years ago this guy has this built Chevelle , couldn't figure out this strange miss. After all...everything was new, all plug wires so neatly bundled together...wires a work of art. Instructor puts it on a oscilloscope (like looking at your heart beat EKG)...the firing pulses...but then sometimes an extra pulse! Why? Teacher cuts all those pretty ties, jumbles wires up...miss is gone. Why?
Induction! Whenever electricity flows through a wire it creates a magnetic field. Another wire close by can pick up field and pass it along. That's how transformers work, two windings of wire ...if it's a 10 to 1 ratio you put 120 volts in you get 12 volts out. An ignition coil is an autotransformer meaning the primary (side screws) have turns of wire then a LOT of turns going up to the center tower. 12 volts in...points closed...it builds up a big magnetic field...points open...WHAM!...20 to 30,000 volts out!!!!!
So battery...to start car/tractor...motors running you can throw battery away...its running on alternator or generator.
Understand I'm speaking generalization...simple enough to understand. Oh...that grease...use it!!!!!
The better the connections the less resistance. Less resistance less heat!
Electricity likes nice clean shiny metal to metal...otherwise it's like corroded leaky water pipes...YUK!!!!!

 

[Industrial Toys]

Something kind of different. Epoxy filled heat shrink. I kind of sorta thought it magically was impregnated in the inner layer of heatshrink, but come to learn it's in between the two layers. I ask you. What good is that? So it flows out the end. It might even be useful if the inner layer was cut back at each end, but that's obviously not possible. So, I really see no point in getting that stuff anymore.

 

[Fuddy1952]

Something kind of different. Epoxy filled heat shrink. I kind of sorta thought it magically was impregnated in the inner layer of heatshrink, but come to learn it's in between the two layers. I ask you. What good is that? So it flows out the end. It might even be useful if the inner layer was cut back at each end, but that's obviously not possible. So, I really see no point in getting that stuff anymore.

This old farm place has some buried wire, not much since I've replaced most, a few places I spliced, soldered, use epoxy filled heat shrink all in a waterproof connector. To me the epoxy shrink makes it waterproof even if other leaks.