Can I run the refrig on AC from an inverter in the tow vehicle?

[RockyMtnRay]

Originally Posted by Bill

The interesting thing is that (in my case at least), I don't recall having this problem when my TM and tow vehicle were new. Something has changed, or perhaps I have become more aware of what is going on. If I ever get my TM back from its new home at the repair shop/aka dealer, I will make some new measurements and post them. Should be interesting.

Bill

If boiled down to one word, that word would have to be corrosion. Or maybe oxidation (yeah, I know, that's just another variant of corrosion). Since your rig spends half the year in the wet, corrosive atmosphere of New England...where acid rain and salt air are common...and you make those twice annual treks across the continent (bet a lot of those miles have been in pretty wet conditions)...there has got to have been at least some gradual corrosion/oxidation in all those junctions that both TM and Ford engineered into your trailer/TV.

One of the things I have going for me is the relatively dry climate of Colorado (to us, a horribly muggy summer day is whenever the relative humidity exceeds 15% ). Furthermore, I try really hard to only tow on dry roads...which isn't as hard as it sounds since about 90% of our summer rainstorms occur in the afternoon. And we have almost no atmospheric pollution...in particular almost none of those nasty sulphur oxides. Stuff hardly even rusts here and electrical contact problems are exceedingly rare.

On my Jimmy there is a separate circuit with #10 wire that goes from the battery, through a breaker and an isolator and to the Bargeman plug and on the TM. There is also a fuse holder in the charge line to the battery, just about six inches from where it hooks to the + post. My question is: does the refrigerator actually NEED to use power from the battery, or can I pull that fuse and run the refrigerator solely on the TV power? Is it a case of the refrigerator is pulling power from the TM battery because it is the circuit of least resistance or is there not enough power to operate the refer coming from the TV? I realize that if I turn the TV off, the refer will not have power, but that would be for very short times and wouldn't allow the refer to warm up. Is this a dumb idea? We go dry camping in northern Washington when the huckleberries are ripe, so we'd like to get there with a fully charged set of TM batteries. Thanks,

[RockyMtnRay]

MOST tow vehicles will provide enough current to the trailer to not only keep the TM battery(ies) from discharging with the refer on 12V but will actually recharge the TM battery under this situation. Just because a FEW people have vociferously and repeatedly posted that THEIR tow vehicle won't keep the TM battery charged while enroute with TM refer on DC does NOT mean that most people will have this problem. In other words, don't panic and start trying desperate workarounds until you KNOW that you have a problem.

Originally Posted by Freedom

On my Jimmy there is a separate circuit with #10 wire that goes from the battery, through a breaker and an isolator and to the Bargeman plug and on the TM. There is also a fuse holder in the charge line to the battery, just about six inches from where it hooks to the + post. My question is: does the refrigerator actually NEED to use power from the battery,
or can I pull that fuse and run the refrigerator solely on the TV power?

Should work...not sure of the exact way the house battery is wired in your TM model. But don't do this until you know you have to do.

Is it a case of the refrigerator is pulling power from the TM battery because it is the circuit of least resistance or is there not enough power to operate the refer coming from the TV?

Essentially the same thing. This is NOT a problem with MOST tow vehicles...the circuit you described your Jimmy as having should NOT have a problem.

I realize that if I turn the TV off, the refer will not have power, but that would be for very short times and wouldn't allow the refer to warm up. Is this a dumb idea? We go dry camping in northern Washington when the huckleberries are ripe, so we'd like to get there with a fully charged set of TM batteries. Thanks,

Before you get yourself all wound up over what may not even be a problem on your rig, get a voltmeter and go do some testing of the voltage at the TM battery. This will be fairly easy since you have a battery on the TM hitch. Before doing these tests have your TM opened up and positioned so that you can back the Jimmy close enough to plug the TM umbilical cord into the Jimmy's Bargman plug. BUT DON"T PLUG THE CORD INTO THE JIMMY YET!

1. Make sure your TM battery is fully charged. Allow an hour or so after you stop charging before proceeding with the following steps (so the voltage stabilizes)

2. Check the battery voltage without any load on it (everything turned off). Should be right around 12.6 to 12.7 volts. If it isn't this high, you already have a bad battery.

3. Go inside the TM, turn on the refer to DC and turn the thermostat to its highest number to insure the DC powered boiler heater comes on and stays on.

4. Check the voltage at the TM battery again. Will probably be down to around 11.9 to about 12.2 volts. Don't panic...this is normal. If it drops to below about 11.3 volts, your TM battery is worn out and needs to be replaced anyway.

5. Start your Jimmy's engine and hook the TM's umbilical to the Jimmy's Bargman plug.

6. Check the voltage on the TM battery again. It should be above 12.7 volts, probably will be over 13 volts. If it's above 12.7 then your Jimmy is providing enough current to prevent a discharge of the TM battery; if it's over 12.9 volts or so, the Jimmy will recharge the TM battery even with the refer on DC. If the voltage is below 12.6, then you do have a problem and will have to take corrective action or do as you thought to isolate the TM battery from the refer.

[Bill]

Ray is right about almost everything - but not quite everything.

I agree with him that you almost certainly do NOT have a problem. Most of us don't - but a few of us (including me) do have it. Regardless of the reason - and there are several - it is real. But as he advises, don't get excited unless you confirm that you are one of the unlucky ones.

I disagree with him that it is OK to pull the fuse at the battery. DO NOT DO THIS! If you do, a critical function will not work. That function, unrelated to the refrigerator, is the BREAKAWAY switch. If your trailer should ever become unhitched from the car (break away) while you are driving, there is a switch on the trailer that applies full trailer brakes, to bring that big hunk of metal to a quick stop. Since the trailer is no longer connected to the car, the only source of power for the brakes is the trailer battery. If you have pulled the fuse, the brakes won't work. That big ol' hunk of metal will sail down the highway, taking out road signs, construction workers, and other cars, until something finally brings it to a halt. You don't want any part in that scenario unless the words "negligent homicide" and "prison" have a special allure for you.

I have been the proud, silent, and usually lone advocate of adding an AMMETER in the battery line. Here we go again. An ammeter will tell you at a glance whether the battery is being charged or discharged, and how fast. A voltmeter won't. A voltmeter tells you how full the bucket is, but in most cases doesn't tell you whether water is being added or is leaking out. You have to wait for a while to see if the level changes. Ray's procedure will, in fact, tell you if the battery is being charged or discharged, so it is adequate for your particular question. But it will give you no clue about how fast either one is taking place. Inquiring minds want to know!

Bill

[YWORRYDOG]

I will now admit sheepishly, that I stated our battery is only ¾ full when we arrive at a campsite. Well, I was not reading the battery indicator in the TM correctly….I thought that the top light would be lit when the battery is fully charged. But now I know that C stands for charging. We can’t all be smart can we!!??

[RockyMtnRay]

Originally Posted by Bill

Ray is right about almost everything - but not quite everything.

<**blushes**>

I disagree with him that it is OK to pull the fuse at the battery. DO NOT DO THIS! If you do, a critical function will not work. That function, unrelated to the refrigerator, is the BREAKAWAY switch. If your trailer should ever become unhitched from the car (break away) while you are driving, there is a switch on the trailer that applies full trailer brakes, to bring that big hunk of metal to a quick stop. Since the trailer is no longer connected to the car, the only source of power for the brakes is the trailer battery. If you have pulled the fuse, the brakes won't work. That big ol' hunk of metal will sail down the highway, taking out road signs, construction workers, and other cars, until something finally brings it to a halt. You don't want any part in that scenario unless the words "negligent homicide" and "prison" have a special allure for you.

BILL IS RIGHT...my bad, I totally forgot about this consideration. The TM battery must be left in the circuit. Do not pull the fuse.

I have been the proud, silent, and usually lone advocate of adding an AMMETER in the battery line. Here we go again. An ammeter will tell you at a glance whether the battery is being charged or discharged, and how fast. A voltmeter won't. A voltmeter tells you how full the bucket is, but in most cases doesn't tell you whether water is being added or is leaking out. You have to wait for a while to see if the level changes. Ray's procedure will, in fact, tell you if the battery is being charged or discharged, so it is adequate for your particular question. But it will give you no clue about how fast either one is taking place. Inquiring minds want to know!

Bill

BILL IS RIGHT AGAIN. Perhaps the usually lone advocate...but not the only one who has put an ammeter in the circuit (did so myself after reading prior advocacy). Extremely helpful to quckly ascertain if the battery is being charged or discharged, and if so, how rapidly.

I had not thought about the breakaway - thanks for bringing it up. I will not remove the fuse! Where exactly would one fasten this ammeter, in the charge line to the battery? Do you know of a good ammeter and do you have a suggestion as to where to purchase same? I assume the ammeter would have to go in series as opposed to hooking up a voltmeter in parallel? I shouldn't use that word (assume) my chemistry teacher said some bad things about it! Thanks for all the good info and QUICK responses! Thanks,

Originally Posted by Freedom

I had not thought about the breakaway - thanks for bringing it up. I will not remove the fuse! Where exactly would one fasten this ammeter, in the charge line to the battery? Do you know of a good ammeter and do you have a suggestion as to where to purchase same? I assume the ammeter would have to go in series as opposed to hooking up a voltmeter in parallel? I shouldn't use that word (assume) my chemistry teacher said some bad things about it! Thanks for all the good info and QUICK responses! Thanks,

Jim,

I'm about to add an ammeter to my 2005 TM2720, which has the battery on the front.

My plan is to add a second battery on a switch so that I can choose to have either battery alone, both batteries in parallel, or both batteries disconnected. I just won't have time for a couple of weeks to get around to it.

You're corect, though. Ammeters go in series on the hot lead. Volt meters go in parallel across the batteries. My plan is to put the voltmeter across the pair of leads that run from the battery to the TM. That way it will measure the voltage of what every battery(s) I have selected. Check around this forum. This topic has been brought up in several threads.

It looks like the best source for the switch is at West Marine. I've been finding out that marine supply houses have a lot more selection for power equipment than an RV store does. Some people have had good luck with solar supply houses. An ammeter may be found at an suto supply store. You will need to that goes from -30 to +30 amps. The volt meter only needs to go up to 15 volts.

[Bill]

Let me expand a bit on the very good info Wayne provided.

There are two different kinds of ammeter you can install. Either way, as Wayne said, something has to go in series with the battery hot lead.

The most straightforward way to install an ammeter is simply to buy one, and wire it into the battery hot lead. A heavy (#10) wire goes from the battery to the ammeter, and a second heavy wire goes back to the original battery connection wire. This is great if you want the meter right next to the battery, but can be unhandy if the battery is on the tongue but the ammeter is inside where you can see it from the couch.

DETAIL: For the TM, you should have an ammeter that reads 30-0-30 amps, or even 20-0-20 amps. As Wayne says, you can get ammeters at auto supply stores, but in my experience, they are all 60-0-60 amps, or even 100-0-100 amps - not too useful in a TM. I have found it better to go to stores that specialize in smaller engines with smaller electrical systems. Among them are tractor supply places. A couple years ago, I bought a couple 20-0-20 amp meters from Trusty Tractor (www.trustytractor.com) for about $7 each. They work fine. Unfortunately, this particular webstore has recently "improved" their web site, so now you can't find anything unless you know the manufacturer and model number of the tractor that uses the thing you want. I rummaged around a couple days ago and found 20-0-20 ammeters for $7.84 each, but I am unable to find them again. This morning I found a 30-0-30 ammeter for an International Harvester Cub for $12. Perhaps a Google search on "tractor parts" would turn up an easier site.

The other way to get an ammeter is to wire a low-value resistor in the battery's hot wire. The resistor can be right next to the battery, so no long wires are needed. When current passes through the resistor, it generates a voltage. You can then run a pair of small wires to a voltmeter, which can be located anywhere.

DETAIL: The low-value resistor is called a SHUNT. With most resistors, the value of resistance is called out in ohms, but when the resistor is used as a shunt, it is called out with a different (though equivalent) description. This is "millivolts per amp". If you have a shunt which is specified as "10 mv per amp", and you run 20 amps through it, then 200 mv will be generated. This is handy, since inexpensive digital voltmeters have a full scale range of +/- 200 mV. When the meter reads "200", you know it means "20 amps". Even better, you can set the location of the decimal point on these meters. If you move the decimal point so the meter reads 20.0 instead of 200, you get a direct readout in amps. The only inconvenience is that these meters need their own 9-volt battery (like a smoke detector), but it lasts forever.

Sounds more complicated than it is.

You can take a look at http://www.rickandbarb.com to see an example of how one guy did this in his RV. On the initial menu, click "Ricks Stuff", then "Motorhome Projects", then "Digital Meter Project". He actually installed 4 meters to measure AC and DC volts and amps in various places in his RV. It is a nice project, but all the meters make his diagram look wildly complicated - we don't do anything nearly as complex to add an ammeter in the TM. He also gives some links to sources for meters and shunts. I can sketch up what we want if anyone cares.

Whichever way you choose to go, an ammeter is a wonderful thing to have.

Bill

Once again you guys have provided me with very good alternatives and information on how to do this. I appreciate your taking the time to educate me on all this stuff that I haven't thought about very much since school and that was a long time ago! I had never heard of the shunt, other than a shunt winding in a starter that limits the speed at which it will run. If I understand you correctly, you're basically measuring the voltage drop from one side of the resistor to the other with your small wires going to each side of the resistor. That sounds easy enough. I agree that Rick's setup looks a lot more complicated than anything I would want. I did like Wayne's idea of a switch to use one battery and then the other - I just figured I would move the wires from one battery to the other. It would be pretty handy to have a switch to do that - especially if it would switch automatically! That's getting too complicated. I wish I had bought two six volt batteries like a lot of you guys since I now understand that they are a lot better as far as deep cycling. I just bought the two batteries on the TM before I found this site. They’re Interstate’s best group 24 “deep cycle” or so they say. When they wear out, I'll figure on putting in a couple of golf cart batteries, and maybe solar panels so we can camp on the beach in Mexico with my brother! Thanks again for all the help,