Towing with generator running

[EMD_Driver]

This subject came up over n rv.net and I thought I ask the opinion of those here. I'm hoping someone might know something that I do not. I understand the wish to run the generator, as the A/C will have the unit cooled down when you get where you are going.


My question is this: What kind of effect would it have on the TV's electrical system, to have the camper's converter running? Wouldn't the 12VDC power backfeed into the TV's electrical system?

[Jim-Bev-2363]

Wouldn't the converter use only what is needed? Kinda like runnig a 12V lightbulb only uses enough to power the bulb and not the complete resources of the power supply system because if it did the bulb would blow all to pieces.

I use to run the generator on the motorhome quite a bit while we were riding. Let the generator run fresh gas while we were in control of what was going on and it never did hurt anthing. Even if we didn't run the roof A/C or other 110V equuipment.

jim

[Gene]

Originally Posted by EMD_Driver

... Wouldn't the 12VDC power backfeed into the TV's electrical system?

That is always a concern of mine. I always remove the shore power before I plug into the TV. With the ignition on and engine running I don't want the converter trying to compete with the alternator and the voltage regulator and computer in the TV. Over the many years I have worked with electrical/electronic stuff I have "fried" enough things by stupid errors that I tend to err on the side of caution.

[Jim-Bev-2363]

Wouldn't running the TVs 12V while running the converter be the same as running two batteries? It is still two 12V supplies isn't it? As long as you have polarities right it should make no difference. The power feeds should be controlled by diodes. Don't alternators have diodes to protect themselves? If the diodes go bad you could have problems whatever power supply you run. If you plug 110V straight into the 12V system you could destroy it anyway but that would only happen if your systems were not working correct to begin with.


jim

[Gene]

Many years back, when alternators were a new thing, I blew one by having a battery charger on the battery while the engine was running. A mechanic at the auto parts store later said Don't do that stupid!. Alternators have improved since then.

[Jim-Bev-2363]

My guess is that your alternator was blown to begin with so you needed the charger hooked up. The alternator already had problems and was not the result of anything you did unless you crossed the battery cables. Ever give another car a jump with jumper cables? The good battery would be like the battery charger you used. If you have polarity correct you should cause no problems. Cross polarity and you can create problems.

jim

[Steve Collins]

Gary, if your TV has a fuse on the 12v charge line, you could pull it which would assure that you won't have any conflicts (real or potential) between the TV's charging circuits and the TT's convertor.

[JohnB]

Originally Posted by Gene

That is always a concern of mine. I always remove the shore power before I plug into the TV. With the ignition on and engine running I don't want the converter trying to compete with the alternator and the voltage regulator and computer in the TV. Over the many years I have worked with electrical/electronic stuff I have "fried" enough things by stupid errors that I tend to err on the side of caution.

I'm going to go with Gene on this one too.

Jim there is a difference between 2 power supplies with charge regulators then a battery banks that is a 12 volt source.

You mentioned diodes on an alternator, well yes it is an alternator not a generator. The diodes create a rectification by the correct phasing of 4 diodes in a bridge to turn the AC current produced by the alternator into DC current the auto runs on.

See here for a quick hit on the web alternator

The convertor Gary has has 3 levels of voltage outputs plus a desulfate mode. The convertor senses the resistance thru the battery on the camper and selects the proper voltage to charge at. And then every so many hours once fully charged it kicks into 14.4 volts to desulfate.

If the progressive dynamics is putting out 13.6 in normal charge but the truck is putting out 13.2 in float some one is going to get mixed up. And then you throw in the boost of 14.4.

I do not know if your going to fry anything but for sure I can't see either charge controller working the way it is suppose to.

Like Steve mentioned if you pull the TV charging fuse out in the 7 wire box where ever it is on your camper that will isolate the 2 and the convertor will work as normal.

What I'm more unknown about is running the AC on while driving down the road. My brain is going to the compressor bouncing around and the oil in the crank case. I'll declare I don't know for sure but would find out for if that is a problem or not. I know on a standard refrigerator that after you transport it you should wait a while to let the oil splashed up all over drain down and then start the unit. On a camper AC compressor don't know if they are all that different.

We use to have a refrigeration member who does this for a living but I haven't seen him post in a long time. If he is reading along hopefully he will jump in.

Calling Dometic may yield nothing. They will not switch you to tech service unless you are a certified Dometic repair shop who has a certification number. They are not like Atwood Mobile or Dexter who will help any customer who has one of their products.

Hope this helps

John

[Jim-Bev-2363]

john,

Wouldn't the pieces of equipment have their own polarity protections to stop the reverse current flow of other equipment? It still seems to me that as long as the polarity of all equipment is the same there would not be any damage. If one does have stronger voltage than the other the current will simply flow the circuit it is connected to instead of trying to flow in a opposite direction. Maybe if the two pieces of equipment were connected head to head there would be problems but they are connected to a complete circuit and will want to flow that circuit before pushing current to destroy other equipment. Well, as long as there is 12V to 12V and 110V to 110V. Maybe if there were a large differential of voltages there might be damage of a blown diode, but I wouldn't think that likely. The voltages will seek their own power source wouldn't they? If they do not have a complete circuit there is only potential without flow.

As for running the A/C while riding. If the A/C were turned on the side and started it might cause problems but that isn't what happens. Yes the compressor will get off level from time to time but aren't the compressors lubricated by splashing the oil inside, oil bath? Kinda like the lawnmower engine? No oil pump so moving parts will lubricate themselves by being physically inside the oil. I don't see the oil in the compressor being thrown so far that it would leave parts dry because it isn't like the holding tank where there is a large area to hold liquid away from moving parts, the compressor is a rather small, compact unit and any force throwing oil away from moving parts would be short lived, if at all, before returning to the lubricating position.

As I said, I did run the generator on the motorhome quite often (until the wires were eaten by rats) without damage. perhaps hundreds of miles at the time. I do not know if there are differences between a generator in a TT and a motorhome. I wouldn't think there is much.

jim

Edited to add: To err on the side of caution is a good thing.

[Jim-Bev-2363]

John,

Here is a diagram for thought. Connect D-Cell batteries as a flashlight circuit to the appropriate voltaged lightbulb. In that circuit insert a common wire, bus bar. Do that with different voltaged "flashlights". It will make no difference where along the Bus Bar you tie each flashlight to they will all operate properly without interrupting the other system or doing damage.



You could take a 110V power source and tie into the bus bar and it would not blow the flashlights. Only once the circuits become mixed will there be problems.


Now replace the bus bar with the house battery. Connect the TT converter to the house battery. off to the side connect the TV alternator. The converter will operate as the one cell flashlight. The alternator will operate as the two cell flashlight. Each has its own circuit.

Now say the converter senses the battery level, what will it really sense? Could that be the output of the alternator? Doesn't the alternator also output for demand? Low battery means higher output, right? If the converter is putting out the 14.4, or whatever voltage, the alternator will adjust appropriately. Both pieces of equipment run according to the needs of the battery which in my example is really the bus bar.

Back to my original thought that each piece of equipment is a seperate circuit and only if there is a problem, damage to, with other systems will there be interaction between the sytems. Voltage will seek its source. converter 14.4 seeks the converter. Alternator 13.8 seeks the alternator. Unless you have a power source greater than the bus bar/ battery can handle will there be problems. Now that 110V input would blow the sytem all to blazes.

jim

[Jim-Bev-2363]

The reason a fridge is to sit after being on the side is not because of the oil in the compressor but for the freon in the system. Refrigeration systems run on liquid and gas sides. When they lay on the side the liquid can move into the gas side. Then when the compressor is started the liquid will slug the compressor and potentially blow it since the compressor cannot compress the liquid. Busted piston instantly.

Compressors are sealed units and the motor runs in a oil bath. No problems going down the road.

[EMD_Driver]

Originally Posted by JohnB

I do not know if your going to fry anything but for sure I can't see either charge controller working the way it is suppose to.

Like Steve mentioned if you pull the TV charging fuse out in the 7 wire box where ever it is on your camper that will isolate the 2 and the convertor will work as normal.

What I'm more unknown about is running the AC on while driving down the road. My brain is going to the compressor bouncing around and the oil in the crank case. I'll declare I don't know for sure but would find out for if that is a problem or not. I know on a standard refrigerator that after you transport it you should wait a while to let the oil splashed up all over drain down and then start the unit. On a camper AC compressor don't know if they are all that different.

I'm going on what I've been told here and that was, that a lot of people in motorhomes run their generators and air conditioners while driving. The difference between them and us, is that their 12VDC systems are isolated by diodes and have switches to allow mixing between the 12V cranking battery and the 12V deep cycle batteries( If necessary)

I'm also wondering if Ford may have a diode installed in the trailer charge wire. One easy way for me to check, is to hook the 7 way plug up while the shore power is still connected. Of course, I would do it while the truck is turned off. I am not sure if the charge line fuse is before or after the relay, but that would also be easy enough to find out. If there is no diode, I could install one easy enough!

[Jim-Bev-2363]

There was a dash mounted switch to seperate the house battery from the truck battery. That was to keep the house from draining the truck starting battery. When traveling I simply connected the two systems together again and both batteries would be charged at the same time.

[Sunline Fan]

Originally Posted by EMD_Driver

I'm going on what I've been told here and that was, that a lot of people in motorhomes run their generators and air conditioners while driving. The difference between them and us, is that their 12VDC systems are isolated by diodes and have switches to allow mixing between the 12V cranking battery and the 12V deep cycle batteries( If necessary)

We did that only a couple times. Once or twice was when it was over 100 outside and anywhere behind the front seats was miserable. The other time was in the summer (80's outside) and the dash air quit working, so we ran the generator and roof air to keep the inside cooler. Never had a problem, but with 40 hours on the generator over six years, we obviously ran it a lot...