Rookie Mistake 102

[Len S]

Originally Posted by Peder_y2k

I think the fuse blew from high resistance in the trailer feed wiring. Excess electrical load will do that with inadequate wiring.

Correction.....fuses blow when current draw through the fuse, exceeds the fuse rating. Resistance in the wiring has no direct effect.
The fuse rating is based on the wire size that will safely handle the current plus whatever component that is being operated.

[DJD]

Originally Posted by Iowa Dave

Sorry to hear you encountered such an expensive lesson and “ fault “ in your hookup. However, this has happened to a lot of folks. On my 2012 Toyota the folks that installed my 7 pin had it hot all the time. In California I stopped for lunch and a visitors center. In about 30 minutes the car would not start. I got a jump and was ok for the rest of the trip but did hear the starter growl a couple times. Upon returning home I had the vehicle in for routine service where they discovered a “dead cell” in the battery and that I had been running and starting on 10.8 volts. The battery was under warranty so I came out fine and came to the realization that the trailer had sucked what little juice I had as starting “freeboard” when I’d stopped and ran some lights and the max fan. On the new Highlander I made sure the tech wired the rig so that the battery was not giving up juice when the engine wasn’t running. I still unplug at the end of the day or on extended stops and check the lights before I get back on the road so I haven’t forgotten to plug back in. When traveling I only run the refrigerator on propane and haven’t ever tried it on DC.
Iowa Dave

- this is but one simple method, but when we stop for an hour or more, we thread a piece of hot pink surveyor’s flagging (about 1” wide) through the steering wheel. This helps you to remember to plug Back in, and keeps you from dragging the rv pigtail across asphalt and concrete streets. Ouch!

[Lisle]

I forgot to chick my wheels the first time I camped in a state park. Very slight incline, but camper slid 6 feet. These mistakes do reinforce doing it right and using yr checklist. Ah but we’re all human and screw up sometimes.

[Jann Todd]

Originally Posted by Doc Wood

Hey, no worries, you aren't the first or last to do that! I did it, twice before I figured out what had happened. Imagine waking up a 5 a.m. on the NY Throughway rest area with a dead battery! Fortunately, one of my first purchases, and I highly recommend this, was a mini charger that I carry in my car. Jumped the car just fine--of course also set off the alarm as I had opened the door with the key and not the clicker so I woke up the truckers parked next to me.

One thing on this thread I do disagree a bit with. I never run my frig on propane while driving. Too many horror stories and who needs a live fire in your trailer while moving down the road. the 12V does just fine, you just need to remember to either shut off the frig at night if you can't plug in or don't want to bother with the propane.

In my 45 years of owning some kind of camping vehicle I've always ran the fridge on propane while driving and have never seen a fridge cause a fire or explosion. Could cause a fire if there was a wreck and gasoline spilled near the fridge and it was on or sparked. But that is very unlikely. Millions of RV'ers drive on highways daily with their fridge on propane. I've seen more fires by generators running so fridges could run on electric while people are driving down the highway but those are extremely infrequent as well. A well functioning fridge on propane won't cause a fire unless you put something flammable in the area of the flame while driving no more than while you are still.

[computerspook]

Originally Posted by DJD

- this is but one simple method, but when we stop for an hour or more, we thread a piece of hot pink surveyor’s flagging (about 1” wide) through the steering wheel. This helps you to remember to plug Back in, and keeps you from dragging the rv pigtail across asphalt and concrete streets. Ouch!

Brilliant

[computerspook]

Originally Posted by jerrybob

I run our fridge on propane or AC...never DC. Also.....I always unplug the trailer if we're gonna be gone more than an hour.....easy to do...keeps you out of trouble.

I always run on 12 volts while on the road. Never have had a problem. Well provided I got it cold in the first place. I run it for a day on ac before I leave so everything is flowing well. I always arrive even over a day away with dual drive with the frig still cold.


Now I do keep my plug clean of corrosion. And I keep my wires going to it and from it in good shape. One way I do that is the box I mentioned. I bought a good socket for both my TV and the parking box. Even if I don't use it for power, I plug the plug into it. The sockets I buy have water resistance in them that helps keep the plug dry.


I also do have a good battery in my TV. So I can park for several hours on 12 volts without a problem. Actually I had an alternator failure a year ago and was able to make it home an hour away running just on both batteries. Yeah I turned off the frig and then drained both batteries to get it home.

[Doctor Harold]

Originally Posted by Raspy

Lisle,

Everything fits together except why the car died while driving. Once running, the car battery should not go dead...

I was a mechanic back in the dark ages when generators and alternators were both common. It may not apply to vehicles now (I think it still does) but generators and alternators are fundamentally different.

Car generators are "self-energizing," which means that when you have a totally dead battery and you jump start the vehicle the generator will charge up the battery while you put on the miles. It doesn't need a battery to energize the field. You can even remove the battery and the generator will supply current to run the car and some, if not all, accessories (lights, etc.). I've seen it done. Someone borrows a battery to get their car started, and then removes the battery and drives hundreds of miles cross country. You just can't shut off the engine. The downside to a generator is it has more moving parts, and runs much hotter, shortening its life, because the charging current is created in the armature and passes through the brushes and commutator.

Alternators are not self-energizing, and need battery voltage to energize the field (which is the rotating part). The brushes only carry the energizing current through slip rings instead of a commutator, so there is little or no arcing, meaning less wear and and they last much longer. The current created in the stator is AC current, and it converted to DC with diodes. If your battery is dead and you jump start the car, enough voltage will be soaked into the battery so that the car will run for a while, depending on what accessories are being used. Ignition uses very little current, but when the battery goes below what the ignition requires, the engine will die. It's said you should never remove or disconnect the battery from a running engine that has an alternator. If you are lucky the car will die and nothing more, but electricity can do funny things when seeking a ground, and expensive components can end up fried.

It was common to service generators regularly to prevent failure. Bearings, brushes, and insulators if needed. Most generators even had oil cups for the bearings.

Alternators are almost failure proof. I have "rebuilt" many alternators, which only required an inexpensive set of brushes and bearings, and it's a much easier job compared to rebuilding a generator. It was almost always a bad bearing (sealed) and was often a fifteen-minute job once the alternator was off the car. Yes, other things do go bad, including diodes, but it's pretty rare unless something else caused the failure, such as a short-circuit, or asking the alternator to do much more than it was designed to do.

I had a friend who specialized in rebuilding generators, including rewinding the field coils (which I knew of no one else who did) turning commutators on a lathe, and soldering in new brushes. He charged top dollar and was always busy. (I know how, but won't.)

Harold

[computerspook]

Originally Posted by Doctor Harold

I was a mechanic back in the dark ages when generators and alternators were both common. It may not apply to vehicles now (I think it still does) but generators and alternators are fundamentally different.



Alternators are not self-energizing, and need battery voltage to energize the field (which is the rotating part). The brushes only carry the energizing current through slip rings instead of a commutator, so there is little or no arcing, meaning less wear and and they last much longer. The current created in the stator is AC current, and it converted to DC with diodes. If your battery is dead and you jump start the car, enough voltage will be soaked into the battery so that the car will run for a while, depending on what accessories are being used. Ignition uses very little current, but when the battery goes below what the ignition requires, the engine will die. It's said you should never remove or disconnect the battery from a running engine that has an alternator. If you are lucky the car will die and nothing more, but electricity can do funny things when seeking a ground, and expensive components can end up fried.

I actually brought 7 cars out of Mexico two days on one battery. And yes all of the cars used alternators so this is not true. Just had to hook the battery up and start the car. Then recharge it and remove it being careful to secure the terminals. Then go to the next car and repeat and etc. (Someone stole the batteries and the charge for new batteries for the gringos was $800 a piece :-( ) It worked. Don't want to do it again, but it did work.

I have also charged up very dead batteries enough to get the car started. And then ran on the dead battery to the battery store. Yeah much shorter distance.

As I said I also have my alternator go out on a trip home with my camper. Actually figured I would be in trouble at the side of the road at some point. But figured that the closer to home when I needed a tow the better. Actually using the two batteries (both were pretty flat by the time I got to the mechanics and got a ride home) I got several hours down the road. (No lights needed)



Now an alternator does use power to start producing power. It doesn't have its own magnets. But once it is powered up it can maintain the power itself. Now it is very possible that the vehicle systems do operate as a capacitor. Probably do.

The real difference is that an alternator actually puts out alternating current which is then rectified into DC using diodes. A generator does this directly using the commutator. It is older technology.

[vanstaats]

For years I happily ran my Casita fridge on propane while driving, then I read that it was dangerous in the event of a wreck and you should NEVER drive with propane on. In fact I thought I'd also read that it's illegal to do so (I'm in AZ). So I reluctantly switched to DC for driving, but I don't like it because every time you shut off the engine you're going to seriously drain battery power. Then you have to switch to propane, and it's just a hassle to be changing modes.
I Love running the fridge on propane. So I think this forum has persuaded me to go back to it during travel -- most people seem to think it's safe.
I also dislike using DC because my 2006 Casita's Dometic 3-way fridge control panel/switch is very temperamental, and it can take some time for me to switch modes successfully. :-(
Oh, and thank you for saying you should take fridge off propane while gassing up, I don't think I had been doing that.
Would the easiest way to do this at the gas station be to simply hit the OFF button on the fridge control? Will the flame immediately extinguish? Or must I shut the tank valves?
I've had so much trouble with battery drainage when dry camping that I don't even want to use the furnace or (non-LED) lights anymore. I've now got a silent catalytic heater and I'm using portable solar lights.

[gordon2]

Originally Posted by vanstaats

For years I happily ran my Casita fridge on propane while driving, then I read that it was dangerous in the event of a wreck and you should NEVER drive with propane on. In fact I thought I'd also read that it's illegal to do so (I'm in AZ). ...

I also have read that its illegal.. In fact I have read that many times. In fact every time I read it, I knew the author was wrong.



There are a few bridges and tunnels where the tank must be off however.

Originally Posted by vanstaats

Would the easiest way to do this at the gas station be to simply hit the OFF button on the fridge control? Will the flame immediately extinguish? Or must I shut the tank valves?..

Good question...

You can try it and see.. you will need open the vent to view the flame somehow when you switch it off. Of course shutting off the valve is best even if there is no flame.

Unless someone can answer that question for the exact same make and model of fridge, I would check it myself. My fridge does not have a control board so no "off switch." Instead it has a rotary control. Chances are the Off position closes the valve at the fridge but I would not want to assume mine works the same as yours when it comes to killing the flame.

I do know that on mine, if I leave the fridge control on the gas position and only turn the tank valve off, then the flame will continue to burn for some time.

The weather and the position of the trailer and fridge to the gas pumps plays a part also. If there is a slight breeze and your tug is stopped at the first outside pump then perhaps the trailer is far from any of the pumps. If the fridge is on the opposite side of any pumps also, and the air is not stagnant, then the risk is reduced. On the other hand, if the fridge is on the driver's (port) side and you pull up to the second pump, then the fridge might well be right next to a pump. That can lead to the situation I referred to where someone splashed gas from the pump hose into the fridge vent.

Still the usual concern is gas vapors which is more of a risk in still air. Always best to make sure the fridge flame is off and even better, the tank valve is off.

[Jon Vermilye]

Originally Posted by Gompka

I know some people have successfully run the fridge on 12v while driving, but it's horribly inefficient on dc and from my testing my 105 amp hour deep cycle can only run the fridge on 12v for about 4.5 hrs before its at 50% capacity. Don't forget the lower the voltage gets the more power the fridge uses. For example on a 12.8v freshly charged battery your pulling 120w/12.8v = 9.375 amps, as that battery gets to 11.8v your pulling 120w/11.8v = 10.169 amps. When your running on 120v shore power, your also using a seperate 120w heating element but then your amperage is 120w/120v = 1 amp, much more efficient. I tow with the fridge on propane and have done so successfully for a couple of years now, i don't want to open up that can of worms so just saying its what I choose to do, not persuading or dissuading you on that one

Just a quick correction -

While some inductive devices such as motors may use more current at lower voltages, the resistance heater in a absorptive refrigerator does not. The wattage does not stay the same when the voltage lowers, the resistance of the element does. Lower voltage = lower amperage, which will provide less wattage.

In the example above, using R=E squared over W results in a resistance of 1.365 ohms. This resistance is built into the heating element and only slightly changes with temperature. At 11.8 volts, the current would be I =E/R or 8.645 amps, & a wattage of 102.011 watts.

This points out another reason for using larger wire sizes for transferring power from the tow vehicle to the trailer. The lower voltage caused by inadequate wiring results in the already inefficient 12V operation of the refrigerator to be even worse than expected.

[Jon in AZ]

If you exclude engine compartment fires in motorized RVs, the single biggest cause of RV fires is electrical wiring. LP explosions and fires, though less common, tend to be spectacular; hence the fear factor.

Yes, having the LP valve open increases slightly the possibility of an LP leak and fire in an accident. The risk is low. Modern LP tanks have an excess flow valve that shuts off the flow of propane in the event of a sudden break in the system, and the tanks themselves are very sturdy. Someone posted a video of a rollover accident with a travel trailer. Both tanks broke loose from the tongue and were visibly flying around and banging against the pavement, tethered by their hoses. No leak, no fire.

Forgetting to turn off the fridge and LP valve when refueling is a bigger concern. If I were going to run with the fridge on propane, I'd put a brightly colored sticker and reminder on the gas cap and the dashboard near the fuel gauge (you really should stop and shut it down before you pull up to the pumps).

Assuming your tow vehicle cannot handle the electrical demands of an absorption fridge on 12V, and assuming you don't tow really long days or in extreme temperatures, I like the idea of putting in some ice or frozen liquids, leaving the door closed, and running with the fridge off.

I also like the idea of switching from an absorption fridge to a 12V compressor fridge. That would be a good opportunity to inspect and upgrade the whole 12V system, which is substandard on some trailers anyway.

Google "causes of RV fires." Lots of good reading out there, along with lots of misinformation. Consider the source and make your own decision.

[vanstaats]

Thank you so much! Great information.

[ThomasC]

Originally Posted by computerspook

I actually brought 7 cars out of Mexico two days on one battery. And yes all of the cars used alternators so this is not true. .

Another old mechanic here. You shouldn't say that what someone has posted is not true unless you are absolutely positively sure you are right. And then you shouldn't anyway.

If one of those Mexico cars was a standard and you tried towing it to start it with no battery or a totally dead dry broken battery it would not have started.

If it was an old car with a generator that still had some residual magnetism in it it would have started.

[computerspook]

Originally Posted by ThomasC

Another old mechanic here. You shouldn't say that what someone has posted is not true unless you are absolutely positively sure you are right. And then you shouldn't anyway.

If one of those Mexico cars was a standard and you tried towing it to start it with no battery or a totally dead dry broken battery it would not have started.

If it was an old car with a generator that still had some residual magnetism in it it would have started.

I am absolutely positive that I did what he said was impossible. I did it that time multiple times to refuel and travel out of the situation we were in. And it absolutely did work. I have done it other times less spectacularly.



As I said in the original past all were modern American cars with alternators. They were not Mexican cars. They were american cars that were in Mexico. If you read my post we did not start them by towing. Actually all with automatics. We used one battery, and a pretty bad one at that to start each one in turn. Waited for the battery to charge back up and then left it running, removed the battery and used it to start the next one. Just made sure the terminals were well protected against short. Yeah it was like over an hour to get everybody ready to go each time. But it did work.

I have started and run a car for shorter periods with a battery that was removed. Mostly by connecting another car's battery to the terminals without a battery with heavy duty trucking jumper cables. Then driving the batteryless car somewhere to get it into a secure situation.

Now if you let the terminals short out you are done for. You generally bolow the alternator.

[ThomasC]

He was just saying that an alternator needs electricity to start working but a generator does not. If you spin up an alternator with no wires connected and poke around with a voltmeter you won't find voltage anywhere. If you do that with a generator you can get voltage.

What you did with the cars from Mexico is you started them and carefully removed the battery but kept the motor running. Once the car starts and the alternator starts charging it will continue to charge even though the battery is removed. It gets the current to maintain it's magnetic field from the electricity it is producing. Everything is fine as long as the motor is running and the charging system doesn't spike out and ruin the electrical system in the car.

[computerspook]

Originally Posted by ThomasC

He was just saying that an alternator needs electricity to start working but a generator does not. If you spin up an alternator with no wires connected and poke around with a voltmeter you won't find voltage anywhere. If you do that with a generator you can get voltage.

What you did with the cars from Mexico is you started them and carefully removed the battery but kept the motor running. Once the car starts and the alternator starts charging it will continue to charge even though the battery is removed. It gets the current to maintain it's magnetic field from the electricity it is producing. Everything is fine as long as the motor is running and the charging system doesn't spike out and ruin the electrical system in the car.

Yeah as soon as we were back in the states we brought new batteries. Was not happy with doing this. The other situations were generally old cars that it didn't matter a lot on.

He actually said that the alternator failed with the vehicle running because the alternator requires the battery to be there to operate. I said that was not true.

[Doctor Harold]

I stand by what I was taught. Having said that, I have no doubt the description of your Mexico experience was accurate.

I think you actually provided the explanation:

Originally Posted by computerspook

.......Now it is very possible that the vehicle systems do operate as a capacitor.....

Let me be more precise:

A properly running generator will produce current when the armature is spun -- without applying outside current.

A properly running alternator will not produce current when the armature is spun -- unless you apply outside current.

A vehicle is not an isolated environment for a generator or alternator. As Tom suggested: You can push-start a generator equipped car with a dead electrical system. You cannot push-start an alternator equipped car with a dead electrical system.

Electronic devices such as car radios contain capacitors, and other devices may act as capacitors as well. (Technically, your ignition coil is a specialized capacitor.) Electricity can do funny things when seeking to complete a circuit, and it isn't hard to imagine that the alternator will find a way to complete its circuit -- and energize itself through some sort of back-feeding process.

It almost sounds like perpetual motion, but it's non-sustainable and will eventually fail. Non-electronic ignitions systems have a wide voltage tolerance and might run for a very long time with little available current, as long as you don't run anything else. I can't speak as to vehicles with a computer, electronic ignition, and a zillion sensors, but I suspect their range of failure is much narrower.

--Harold

[Jon in AZ]

Originally Posted by Doctor Harold

I can't speak as to vehicles with a computer, electronic ignition, and a zillion sensors, but I suspect their range of failure is much narrower. --Harold

We’re talking about a modern hybrid power train here, so even more complexity, electrically speaking. Whatever caused the OP’s vehicle to shut down while towing is above my pay grade... and apparently above the pay grade of whomever wired the charge line.