12volt system not working

[Rocketman]

Ohm's law is not challenged by this behavior. The effective load (or R in this case) also does not remain constant. Refer to my earlier comments regarding convertors or voltage regulation circuits on the input side. The effective parameters change by virtue of the regulation circuit, to maintain a controlled output power generally at a regulated voltage, again within the limits of the regulators design. Rest assured none of this behavior will violate V=IR. There are numerous Youtube videos online about regulator and convertor design and operation that will walk you through all these designs and their behavior across varying voltage scenarios, if you wish to explore the concept further.

[David Tilston]

Originally Posted by Rocketman

Ohm's law is not challenged by this behavior. The effective load (or R in this case) also does not remain constant. Refer to my earlier comments regarding convertors or voltage regulation circuits on the input side. The effective parameters change by virtue of the regulation circuit, to maintain a controlled output power generally at a regulated voltage, again within the limits of the regulators design. Rest assured none of this behavior will violate V=IR. There are numerous Youtube videos online about regulator and convertor design and operation that will walk you through all these designs and their behavior across varying voltage scenarios, if you wish to explore the concept further.

For AC motors it's not quite as straight forward, as if active components are straight forward. AC power is weird though. I'm not sure I understand it exactly. First off the resistance is actually more inductive reactance. It is still measured in ohms though, but it is not fixed like a regular resistor is. It varies according to frequency, and is opposed, (reduced) by capacitive reactance, also measured in ohms. My electricity teacher in high school electrocuted himself demonstrating this relationship. Made for a memorable lesson.

AC motors draw power according to the load. If voltage drops, (P=V*I,(current)) then more current is required to provide the power.

[jwcolby123]

Originally Posted by Choosethisday

"If your battery starts to go dead and voltage on the system drops, causing the current to rise"
Whatever happened to Ohm's law?

Ohm's law is for pure resistance. Not a battery, not a refri, not a fan, not anything other than a pure resistance.


Of course this has already been discussed apparently. Nope, I still haven't read every post. Unlikely as well, particularly since the OP has bailed.

[CarlD]

[QUOTE=jwcolby123;825586]

Ohm's law is for pure resistance. Not a battery, not a refri, not a fan, not anything other than a pure resistance.

THIS IS A BOGUS STATEMENT!!

Ohm's law is for everything. It is true for sinusoidal steady state analysis, transient analysis, DC circuits, resistance, capacitance, inductance, etc.

V = IZ is the general form where Z = Zr +jZx, where j is the square root of -1. Zr is the real component ( generally designated ad R), and Zx is the reactive component. Zx is either Zl for inductive circuits and Zc for capacitive circuits. For capacitance Zc = 1/jwC and for inductive components Zl = jwL. In DC steady state analysis, Zx is 0. Transient analysis is used in both AC and DC circuits. Details are available in any circuit analysis text book.

[David Tilston]

[QUOTE=CarlD;825589]

Originally Posted by jwcolby123

Ohm's law is for pure resistance. Not a battery, not a refri, not a fan, not anything other than a pure resistance.

THIS IS A BOGUS STATEMENT!!

Ohm's law is for everything. It is true for sinusoidal steady state analysis, transient analysis, DC circuits, resistance, capacitance, inductance, etc.

V = IZ is the general form where Z = Zr +jZx, where j is the square root of -1. Zr is the real component ( generally designated ad R), and Zx is the reactive component. Zx is either Zl for inductive circuits and Zc for capacitive circuits. For capacitance Zc = 1/jwC and for inductive components Zl = jwL. In DC steady state analysis, Zx is 0. Transient analysis is used in both AC and DC circuits. Details are available in any circuit analysis text book.

Wait! square root of -1?!?! An imaginary number? That is not what my high school electricity teacher taught me, (he is going to be so proud of me). How I learned to calculate:
Inductive reactance: XL=2πfL where f is frequency, L is inductance and π is pi.
Capacitive reactance: XC=1/(2πfC) where C is capacitance
This makes them respond to frequency inversely to each other. Before digital tuning, this was how the tuner on a radio worked.

The electrocution of my electricity teacher was the result of demonstrating something called a tuned tank circuit. That is when the inductive reactance and the capacitive reactance are the same value in ohms, they cancel out. This means that there is nothing limiting the flow of current, other than actual resistance. However, (and this is where ohms law comes in) the voltage across both the coil, and the capacitor is still a function of the current * the resistance, (reactance). I don't remember the exact circuit, so I will make up the following values.

The circuit that the teacher built was meant to plug into a standard 120VAC receptacle. Let’s say the coil had an inductive reactance of 420 ohms and a resistance of 100 ohms as well. To cancel out the 420 ohms of inductive reactance there was also 420 ohms of capacitive reactance, in series. This left only the resistance of 100 ohms in the coil to limit current to 1.2 amps. The capacitor however still has 420 ohms of impedance:
V=I*R=1.2A*420ohms=504 volts (I remember the teacher calculating a voltage in this range)
This is what the capacitor was charged to. After he pulled the plug, he was explaining the theory of how we could get 500 volts when plugged into 120 VAC. He was fiddling with the plug from the circuit in one hand, and the bench ground with the other. Suddenly his eyes go wide and he starts swearing and pacing the room. He had discharged the 500 V on the capacitor from one hand to the other.

As for the imaginary number, I kind of get it. VA reactive is also called imaginary power. Power factor is the proportion of real power / imaginary power.

[jwcolby123]

[QUOTE=CarlD;825589]

Originally Posted by jwcolby123

Ohm's law is for pure resistance. Not a battery, not a refri, not a fan, not anything other than a pure resistance.

THIS IS A BOGUS STATEMENT!!

Ohm's law is for everything. It is true for sinusoidal steady state analysis, transient analysis, DC circuits, resistance, capacitance, inductance, etc.

V = IZ is the general form where Z = Zr +jZx, where j is the square root of -1. Zr is the real component ( generally designated ad R), and Zx is the reactive component. Zx is either Zl for inductive circuits and Zc for capacitive circuits. For capacitance Zc = 1/jwC and for inductive components Zl = jwL. In DC steady state analysis, Zx is 0. Transient analysis is used in both AC and DC circuits. Details are available in any circuit analysis text book.

These all involve time related components. There is a reason it is called impedance and not resistance.

[David Tilston]

[QUOTE=jwcolby123;825610]

Originally Posted by CarlD

These all involve time related components. There is a reason it is called impedance and not resistance.

Your point?

[parmm]

I think Joy got fed up with all our ramblings on 9-10-2021 at 03:52 PM. Can't say I blame her as we turned it into a Electrics 101 course. Hope she found the issue!

[TeresaT]

Originally Posted by David Tilston

It can be replaced:
https://www.ebay.com/itm/203415042938

Thank you! It’s ordered

[Joy A]

<<UP DATE>>

So you know the old adage "If you want something done correct do it yourself"

It certainly applies here. I had a friend check all the fuses including the one under the couch. Guess what...he didn't. I decided to recheck everything.
Well, the fuse under the couch was nolonger there, just a big burnt spot with rat fur bonded to a plastic box I had under there.

I called the factory to find out if my recollection of a 20A fuse was correct. They virtual didn't know what I was talking about. WHAT FUSE UNDER THE COUCH.!!!

Evidentally they stopped putting it in. In fact, they weren't sure what it was even for. I told them it's an inline fuse on black wires. Finally one of the repair persons did say he remembered the fuse and that people had had them burn. But he really did not know what it was for, either. Their conscience is that it's not needed as they do not put it in. They suggect that I simply connect the two wires no fuse necessary. But what does the black wire go to??? They couldn't say.

But what I want to know is "Why did it blow and burn". My DC usage is basically, the lights, furnace and DC outlet (charging my Ipad and Iphone.), so very little.

I'm still leaning to the DC outlet as the problem as I had started using it more. When I unplug from it I hear the wires strike metal, the furnace. I wonder if that wire is worn and causing a short.

Now the DC outlet must have been put in before the furnace, because it is behind it. Right now I am not taking the furnace out to find out. it would seem if I remove the sink I could see back enough to inspect the wires. To me that is the easier way to go.

So, I am not doing this anytime soon. I have the trailer battery disconnected from the trailer and I'll worry about this at a later date when I have a place to empty the trailer out sufficiently to access what I need to.

So there you are the update.

[AC0GV]

Originally Posted by Joy A

<<UP DATE>>

I called the factory to find out if my recollection of a 20A fuse was correct. They virtual didn't know what I was talking about. WHAT FUSE UNDER THE COUCH.!!!

The only reason I could ever see for the second fuse was to protect the Scamp and the tow vehicle from each other. In reality the the tow vehicle fuse should do that. You got out of Wisconsin just in time, it's cooling off this week. (this old diagram shows the fuse)

[Joy A]

Thanks Ken,
That looks familiar, I think it's in my Scamp book.

Still in WI, headed to Shawano for Olive's grooming then on southward. Sitting at Black River Falls at the moment.

[Joy A]

I forgot the fantistic fan. I do run it on DC so my consumption of power isn't much. Oh, and all the lights are LED. Wouldn't seem over loaded to me, don't know why that fuse would burn.

[Dan Meyer]

The fuse under the bunk is there because there might be a circumstance where the tow vehicle is supplying 20 or 30 amps from the tow, and 30 amps from the camper battery. 50 or 60 amps is more than what the wiring in the camper can safely carry, so you need a 20 amp fuse under the bunk.


If Scamp has done away with this fuse they are depending upon the fuse in the converter to protect this wire; in my opinion this is a bad idea. If the insulation in the wire between the tongue and converter is worn and shorts out there is no fuse to protect the wire from overcurrent. Yes, this is unlikely but is a possibility especially after many years bouncing down the road.

--Dan Meyer

[David Tilston]

If the 20A fuse is blowing, then there is more than 20A flowing. If it is fused at 20A let’s hope that the wire is 12 Gauge, or it is already overloaded. Removing a fuse because it blows is like turning off your smoke detector because it reacts to smoke.

What you have is a fire hazard. I would be very concerned.

I have looked at the wiring diagram. The only things being supplied by this wire are the lights, (and the previously discussed fan). This should not total more than 10 amps. However, there are also two taps from this wire that go to the converter. I assume that one of these taps provide power from the converter to charge the battery, (while still running the lights and fan) when the trailer is plugged in. The other would be to supply 12VDC to the converter, from the battery, when the trailer is not plugged in. This means that the fuse under the bunk is also carrying the power for the refrigerator, pump, furnace and TV booster. This could easily add up to more than 20 amps.

The only solution that I can see is to re-wire the black wire, right from a tow vehicle plug, with #10 +12VDC and -12VDC conductors and #12 for the brakes to the 12VDC input to the power converter, (not output), to a #10 wire with 90°C rated insulation, and change the fuse to a 40A fuse. The -12VDC wire should also be changed. I have highlighted the wire that I suspect requires modification in the wiring diagram below. It would be necessary to confirm which wire is the 12VDC supply to the converter.

What is the wire gauge being used in other Scamps for these wires?

[Joy A]

One big change is that I have been using everything in the trailer more these last 2 years than I did in the previous 19. The furnace got used alot last winter and the prior winter. where before I hardly ever was out in very cold weather.

So as my title says I have a new Tow. 2019 Ram Longhorn 5.7 Hemi It's my opinion that the Ram is working better at throwing juice to the trailer battery. I concluded this because the Jeep Cherokee didn't, it couldn't keep up with the Refridge on D/C. With my Ram I ran the fridge on D/C twice and the battery kept up. Now that was just a test. I'm still not inclined to use the Frige on D/C at all.

I should also say that the runs with the Jeep were about 7hr drives where the ones with the Ram were 5 to 6 hrs.

[Glenn Baglo]

Originally Posted by Joy A

It's my opinion that the Ram is working better at throwing juice to the trailer battery. I concluded this because the Jeep Cherokee didn't, it couldn't keep up with the Refridge on D/C.

Wiring for the 7-pin needs to be 10 gauge to deliver enough power. It could be that the Jeep was wired with 12 gauge, which is common. I had to specify 10 gauge when I had my RAV4 wired.

[Natalie21]

Look for ground faults in the wiring. Ground faults can cause the system to shut down for safety reasons.

[CalCop]

I noticed that you keep mentioning the 12volt plug. Is it possible that your device charge rate is too demanding for the circuit? This could cause the wires to heat and possibly overheat.
I remember plugging a USB adapter into to 12volt. I added my phone and tablet and this caused the socket to get warm. Eventually the tablet started beeping as if it wasn't getting power. Later I added a powered USB hub and the issue was solved.

[Natalie21]

If you're running too many appliances simultaneously, it could overload the 12-volt system and not work. Try disconnecting or turning off some devices and see if that restores power.