Like some opinions on this idea!

[Hogballvol]

Hi,
Well I sold the TD I was going to fix up but couldn't due to shoulder surgery and I now have a small standy. It is good but no wiring at all. We are on the grid and off the grid about 50/50, so I am going to separate 12v DC and 110v AC, with the shore power going to a small (fairly ineffecient) fridge and small air cond, electric griddle, and a couple of outlets.

Here's what I'm thinking and would like some comments:

I've got a cheezy harbor freight 1000/2000 watt inverter that I have rigged up on my TV. We just use it while driving (kid watch dvd player, recharge batteries, etc) and it is connected directly to the TV battery. I was going to run a 2 flat plug to charge the camper battery from the TV battery, but now I am thinking of just running an extension cord from the inverter in the TV to a smart charger in the camper, that way I can also plug my 110v fridge into the inverter while driving down the road, killing 2 birds with one stone. whatcha think?

Thanks,
HB

[Ward]

There may be someone here with more electrical knowledge than myself (I already got called out on a breakaway battery)

Thats alot of cord to be running it will cut down on your output, and also you will need to be sure to have the inverter switched so not to run your TV battery down.

Other than that if your inverter will carry everything you should be fine.

[Corwin C]

Depends upon the fridge. Your 1000 watt inverter is only going to provide a little over 8 Amps @ 120 V. The 2000 watt number is surge capacity. Don't try to use that extra wattage continuously or something will fail prematurely. Even for just the fridge it may not have the umph to do it. Every electrical appliance should have information on them somewhere that tells the amperage or wattage requirement. Add it up and make sure you don't go over what's available. The air cond, griddle, etc. are more than likely too much.

Also, don't forget to shut down the inverter when the TV isn't running or with that big of a load you will have a dead battery rather quickly. It is a simple way of accomplishing what I believe you are trying to do, but the process of converting 12v to 120v and back to 12v is rather inefficient.

What I would do ... see if the inverter is enough to run the fridge, if it is, it'll keep the groceries cold en-route. However, I'd charge the battery using the conventional 12v connection to the TV.

[starleen2]

Here's an idea - If you are worried about the fridge keeping things cold while you travel. The night before, plug in the fridge and load it down with what you are going to carry. Then in the morning unplug it and bungee the door shut. This should keep your stuff cool for the duration of the trip or at least 24 hrs. As long as it stays shut - it's as good as a well insulated cooler. That what we do in the ladyBug when we travel. BTW - you'll need at least three times the wattage to start a fridge than what it's rated at.

[Hogballvol]

Thanks large for the input!

Starleen - great idea, that is part of our pre trip ritual!

I should have been a bit clearer. I only plan to use the inverter while driving the TV, so the only 120V thing running will be the fridge (it's actually a "cooler") and it draws about 3 amps = check this math it says 292 kWhrs/yr, 8,760 hrs/yr gives 0.03333 kW at 12 volts ~ 3 amphrs?

I'll really only use it (the inverter) when travelling 2-3 days to get from point A to point B, then it will be straight up shore power or 12V - this is where I should be clearer - I only run the heavy stuff if I have shore power, 12V is only used for the vent fan and some LED lighting, so that allows me to stay 4-5 days on the deep cycle battery.

So if the cooler calculation is correct, it should leave me about 5 amps charging the deep cycle battery - now I'll have to account for the "inefficiencies" (including cord length)- hmmmm back to cost/benefit analysis!

Thanks again!
HB

[N6NG]

Here is what I have planned for my TD. I plan to use one side of a two outlet
110vac for the 110v from the Inverter and the otherside for the 110 from the outside source when available.

http://groups.yahoo.com/group/teardroptrailers/photos/album/885027046/pic/233099931/view?picmode=&mode=tn&order=ordinal&start=21&count=20&dir=asc

Hope it works

Dennis

[bdosborn]

I should have been a bit clearer. I only plan to use the inverter while driving the TV, so the only 120V thing running will be the fridge (it's actually a "cooler") and it draws about 3 amps = check this math it says 292 kWhrs/yr, 8,760 hrs/yr gives 0.03333 kW at 12 volts ~ 3 amphrs?

Not quite, 292 kWhrs/yr is the energy usage, not the power requirement. The refrigerator doesn't run all the time so there's no way to calculate power from this number. Also, the HF inverter has a modified sine wave output and motors draw more current and run hotter on a MSW inverter.

A conservative guess is that your fridge uses 6 amps at 120v; that's at least 70 amps at 12V (includes inverter efficiency and cable losses) that the alternator has to supply to the inverter. That's too big to feed from the cigarette lighter and you'd better check your car's alternator capacity. The inverter will need big cables to feed it, probably at least #4 cables so you'll want the inverter as close to your auto battery as possible or the cable gets bigger due to voltage drop. You'll need at least the 1000 watt inverter because motors draw a lot of current when they start-up.

You'll be running 120V along your vehicle and trailer frame. Make sure you do a real good job installing the cable or someone could get zapped if the hot rubs through and touches the frame.

So it can be done, I've read posts from guys with big motor homes (with big alternators) that have done it but not from anyone that has run 120V from their tow vehicle. The weak link is probably the car's alternator, I doubt it will provide 70 amps over what its already putting out to run the car.

Bruce

[Hogballvol]

cleared up the power vs energy usage ~ that will help in the future.

Also, I should say that I run the 1000 watt inverter directly from the battery posts with 4 feet of extra #2 romex cable I had laying around... since the fridge will be cycling on and off, do you think the alternator (assume 50 amps) could handle it?

Really just curious now, I will probably go with a smart charger and let it go at that.

I really appreciate the help from this board! thanks again,
John

[bdosborn]

since the fridge will be cycling on and off, do you think the alternator (assume 50 amps) could handle it?

I doubt it. I've burned out alternators just by adding running lights but YMMV.

Bruce