Inverter use while boon docking??

Recently while boon docking we arrived at the remote site with a dead TM battery.  Only water we had, we had just poured into our holding tank. Only toilet besides the woods was our TM. Our tent camping friends had a 700 watt ( 1400 peak) power inverter for "car,truck, boat, rv". In order to use our water pump and toilet, we attached the inverter to our tow vehicle battery, ran an extension cord to the TM AC cord, and turned on the inverter when we needed to supply power to the TM. Didn't use lights, used propane for refrigerator and cooking.

Was this an okay arrangement for the TM equipment? Could we have run the furnace fan which Suburban says needs 2.8 amps? (2.8 amps X 110 volts = 308 watts) This particular inverter has a low battery indicator so one is alerted if the tow vehicle battery is being drawn too low.

I've got a lot to learn about RV electricity and would appreciate input from more experienced TM owners.

Thanks,

[Bill]

Well, clearly it works, as you discovered. And when you have an emergency situation, and need it - well, you need it. And there is nothing dangerous or damaging about the hookup. But you stumbled across the least efficient way to use your tow vehicle's battery power, and you shouldn't plan to make this your default method of operation.

To summarize your post, you had a source of 12-volt power (your tow vehicle's battery), and you used that power to operate some 12-volt appliances (your water pump and the toilet pump). But in between the two, the setup converted 12-volts DC to 115-volts AC (in the inverter), and then converted 115-volts AC back to 12-volts DC (in the converter). Both of these conversions are very inefficient, in the sense that they waste power. For every watt that came out of the battery, probably only half a watt was delivered to the appliances. You handled it well since you hooked it up only when you needed power, and then disconnected it. As a result, not a lot of battery capacity was wasted. Good instincts!

Inverters are horrible - but that is a personal rant of mine, and some people disagree. Using propane in a dry campground is an excellent idea, and everyone will agree with that. So overall, you done good in an uncomfortable situation! Good for you.

The furnace fan is a true power hog - you can't run it long (a few hours) unless you have a good way to recharge your battery. If you had tried to use it with the dual conversion setup you describe, the low-battery cutout would have tripped out pretty quickly. There have been several threads here discussing the furnace fan, as well as threads discussing various ways of recharging the battery - including a good thread on solar power.

The real question is, why did your rig arrive at the campsite with a dead battery? You need to fix that, and we (the group) will be glad to help if you need it.

Bill

[Sinclue]

Wouldn't it have worked to just leave the tow vehicle connected to the trailer as if you were traveling and not bothered with the inverter at all?  
That way, if your TM battery isn't shot, you can run your tow vehicle and do some recharging of the battery too.  Then again you should also check out the threads on solar panels.  One 75w panel could replenish your battery to the tune of 4amps per hour in the sun.  At this time of the year you should be able to get 8+ hours of good sunlight.  
I also confess that until I put in my new battery setup (2 6v batts)and the solar panel, I always carried an extra charged battery for just such emergencies or to extend the boondocking experience.  
Jim

[Carol]

Another option that we tried and found to work when dry camping was to take our extra 12V battery in the truck with us to recharge while driving around (with the windows open, of course). We hooked it up to an inverter that we bought from Camping World that had alligator clips on it (as well as a 12V and AC outlets).  So the tow vehicle (truck) battery charged the inverter and the attached battery while we were sightseeing.

This inverter has a small battery of it's own and allows for extending it's "life" by attaching a 12V battery as needed to supply extra operating power. We originally bought it to use as an inverter, for inflating truck/camper tires and for emergengy backup power at home and while camping.  

We thought that it might also work the other way and charge the attached battery. We were correct and found that the inverter would charge the internal battery and then charge the extended battery attached via the alligator clips.  It is called XPower  Portable Powerpack.  I think we got it on sale a couple of years ago when they first introduced it. http://www.campingworld.com/search/i...p;x=10&y=8

It is not advertised to charge an auxiliary battery, but it just considers any battery attached to it as an extension of itself.

Simpler than installing solar panels and cheaper/quieter than running a generator! ;D

The real question is, why did your rig arrive at the campsite with a dead battery?  You need to fix that, and we (the group) will be glad to help if you need it.

Bill

Thanks for you detailed response. It helped me understand what was going on electrically. It is good to know that our "rig" can't hurt the TM.  Yes, we do need help. I posted the details on what we think is the issue in:

http://tretta.hypermart.net/cgi-bin/...num=1045840115

To briefly reiterate. We tend to drive a number of days in a row before stopping for an extended stay. We run the refrigerator on 12V while traveling and only stop briefly during the day while in route. It appears that the refrigerator is draining our battery en route at a faster rate than it is being recharged. We've come up with (hopefully) an ok way to recharge with the Battery tender when we have AC. But I need to know if that method is ok while battery is connected to the TM. Additionally, need to know how to problem solve the drain on the TM battery. The battery has been tested by the manufacturer and is not the problem.

Any and all help will be appreciated. Our next extended trip is in mid August so we have some time to problem solve.

Betty Ann

Wouldn't it have worked to just leave the tow vehicle connected to the trailer as if you were traveling and not bothered with the inverter at all?    
Jim

That's a possibility we didn't think of. Will have to try and see if it works.  Thanks for the idea. Maybe your post will help some other poor soul with a dead battery.

Another option that we tried and found to work when dry camping was to take our extra 12V battery in the truck with us to recharge while driving around (with the windows open, of course). We hooked it up to an inverter that we bought from Camping World that had alligator clips on it (as well as a 12V and AC outlets).  So the tow vehicle (truck) battery charged the inverter and the attached battery while we were sightseeing.

This inverter has a small battery of it's own and allows for extending it's "life" by attaching a 12V battery as needed to supply extra operating power. We originally bought it to use as an inverter, for inflating truck/camper tires and for emergengy backup power at home and while camping.  

We thought that it might also work the other way and charge the attached battery. We were correct and found that the inverter would charge the internal battery and then charge the extended battery attached via the alligator clips.  It is called XPower  Portable Powerpack.  I think we got it on sale a couple of years ago when they first introduced it. http://www.campingworld.com/search/i...p;x=10&y=8

It is not advertised to charge an auxiliary battery, but it just considers any battery attached to it as an extension of itself.

Simpler than installing solar panels and cheaper/quieter than running a generator! ;D

Carol, that is an interesting contraption. Thanks for your input. What type of battery did your recharge? We found not all chargers will recharge a deep cycle battery completely. May be able to mimic your setup with our Battery Tender. At least I'm learning that I have to check how many amps a piece of equipment requires  

[Carol]

bbeckham -

We have Interstate Deep Cycle Marine/RV bartteries - group 27, I believe.

We wouldn't have tried this, but I read a post on a newsgroup about doing something similar to this to recharge batteries while driving around. They did it via a long cable into the truck bed, but we just put it in the back seat of out X-cab with the DC plug in the cigarette lighter. Keeping windows open is a must for ventilation!

We tested the battery after the sightseeing recharge session, and the battery was fully charged. We just wish we had tested the theory earlier as we were cold weather dry camping and limited the use of the furnace drastically to allow our couple of batteries to last a week.

I don't know what your battery tender consists of, but maybe you could recharge your batteries with it.  Good luck figuring out why your battery is discharging so much while traveling. We have run our frig on DC while traveling with the fan on and the battery is fine when we get to our destination.  Some people say to disconnect the trailer plug if you stop during the day for extended periods. We just stop for a half hour at a time max so we don't disconnect the trailer power plug when stopped.

[Bill]

While you are travelling, the tow vehicle should charge the TM battery.  When you arrive at your destination after several hours of travelling, the TM battery should be fully charged.  This is basic truth.  If it isn't happening, then you can band-aid the situation with various battery charger and inverter lash-ups, but they are just masking a basic problem.  We (you) need to find that problem and fix it.

1.  You say you have a new battery, and that a battery shop has tested it and found it to be good.  That's good news.  And as part of this, I assume that the battery water level is correct.

2.  Since the battery is not being charged by the tow vehicle, then either

(a) the tow vehicle isn't providing enough current to run the refrigerator.  The refrigerator draws only 10-12 amps.  The tow vehicle should have no problem providing this much current. If the tow vehicle doesn't provide this much current, the the TM battery will attempt to make up the shortfall, and you will arrive at your destination with a dead TM battery.  

or

(b) Something in the TM (something in addition to the refrigerator) is sucking a lot of additional current, and the total is more than the tow vehicle can provide.  If there is a phantom load in the TM that is sucking perhaps another 15-20 amps, then the tow vehicle might not be able to cover the total.  I can't think of what such a phantom load could be, but it is possible.  To your knowledge, are there any other electrical loads while you are travelling?  Are there any lights on?  Are you sure you have turned off the furnace blower (even though the propane is off)?

3.  If there is no phantom load, and the tow vehicle is expected to supply only enough current for the refrig (10-12 amps), and if it can't do it, then you need to know why it can't.  Possibilities:
a) Undersized alternator in the tow vehicle.  But I think you said you have a tow package.  That should include a hefty alternator.
b)  Bad (loose or corroded) wiring somewhere between the alternator and the TM battery.  This is the usual cause of charging problems, but is hard to localize.  The usual spot is corrosion in the connector between the Tow Vehicle and the TM.  Give both halves a good visual inspection, and brush out any corrosion.
c)  As a variant of b), there could be a blown fuse in the Tow Vehicle's charge line.

You've done the basic work - verifying the battery.  Now, you need to know how much current the tow vehicle is providing, and how much of it is reaching the battery.  Do you have access to a DC voltmeter (VOM) and a DC ammeter? Do you know how to use them?  Without them, it is hard to localize the problem.

So far this isn't of much practical help, I know, but we will zero in on it.  It is not normal to arrive at a destination with a discharged battery.

Bill

1.  You say you have a new battery, and that a battery shop has tested it and found it to be good.  That's good news.  And as part of this, I assume that the battery water level is correct.

Bill

Yes the water level is correct.

(b) Something in the TM (something in addition to the refrigerator) is sucking a lot of additional current, and the total is more than the tow vehicle can provide.  If there is a phantom load in the TM that is sucking perhaps another 15-20 amps, then the tow vehicle might not be able to cover the total.  I can't think of what such a phantom load could be, but it is possible.  To your knowledge, are there any other electrical loads while you are travelling?  Are there any lights on?  Are you sure you have turned off the furnace blower (even though the propane is off)?

Bill

All lights are off except exterior lights. Positive the furnace is off. I can think of nothing else which has any draw except the refrigerator.

3.  If there is no phantom load, and the tow vehicle is expected to supply only enough current for the refrig (10-12 amps), and if it can't do it, then you need to know why it can't.  Possibilities:
a) Undersized alternator in the tow vehicle.  But I think you said you have a tow package.  That should include a hefty alternator.
b)  Bad (loose or corroded) wiring somewhere between the alternator and the TM battery.  This is the usual cause of charging problems, but is hard to localize.  The usual spot is corrosion in the connector between the Tow Vehicle and the TM.  Give both halves a good visual inspection, and brush out any corrosion.
c)  As a variant of b), there could be a blown fuse in the Tow Vehicle's charge line.

Bill

Yes, we have a factory installed tow package. Will check with Toyota to see if it is a "hefty" alternator.

The receptacle on the Toyota for the 7 prong plug was newly installed when we bought the TM last summer. Visually it looks great. I suspect we've had undercharging problems from the beginning. Bought the new battery last Fall because the battery which came with the TM was old and not charging well. We had a boon docking trip coming up and needed a dependable battery.

There is a very small amount of corrosion on one of the set of 7 female clamps on the TM side. The brass looks tarnished on all of the clamps but that doesn't surprise me. Of the seven clamps, 2 are spread farther apart than the other 5 and thus would not clamp as tightly on the male prongs on the tow vehicle side. These I consider suspect.

Will brush the clamps and see if we can close the gap on the two which seem somewhat "sprung".

How do I locate the fuse in the tow vehicle's charge line? Would that be in my Toyota owner's manual or is it part of the plug installed on the Toyota? How does one determine which is the charge line?

Now, you need to know how much current the tow vehicle is providing, and how much of it is reaching the battery.  Do you have access to a DC voltmeter (VOM) and a DC ammeter? Do you know how to use them?  Without them, it is hard to localize the problem.

Bill

Know we have a voltmeter. Will check on the ammeter. My knowledge of how to use them is very elemental. Usually limited to checking small batteries, checking continuity in wiring. Very simple stuff. But if I know what I am supposed to look for (readings) I'm optimistic that I can turn up someone who can help me accomplish the task. My guess is that I need to know volts and amps coming from the tow vehicle. If that tests ok then testing what passes through the 7 prong plug to the TM. Would guess this will be somewhat more complicated.

Thank you very much for taking the time to problem solve in such detail. We'll get started on what we can do right away. As we get things eliminated, I'll post our progress.

Betty Ann