Running the trailer off the tow vehicle battery

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Running the trailer off the tow vehicle battery

Postby TomS » Fri Jan 21, 2005 12:18 pm

I'd like to save weight anywhere I can since I have a small tow vehicle (Toytota Rav/4). If get rid of that big o'l box of lead 'n' acid, I can save 50 or 60 pounds off the weight of my tear.

I can install an effecient flourescent overhead light in the cabin along with some LED reading lights. I have a nifty butane backpacking lantern that would be perfect for lighting the galley. I can use use iPod type device and some AA battery powered portable speakers instead of a car stereo for the trailer's entertainment system.

Based on our tent camping patterns, I don't believe we'll use the interior cabin lights very much. We'll probably only run them a few minutes each evening as we get ready for bed.

I understand the difference between automotive starting batteries and deep cycle batteries. Specifically, If I repeatedly draw down my car's battery, I'll kill it. However, my tow vehicle is equipped with a remote starter (something I really appreciate this time of year). I could always start my tow from inside the trailer to run the alternator for a while if we need to run the cabin lights for an extended period of time.

Since my primary objective here is weight reduction, not necessarily cost savings, I'd consider installing a dual-purpose marine type battery in my tow vehicle if necessary.

The other idea I'm considering is to use a smaller, lighter sealed lead-acid UPS battery instead of the deep cycle battery.

Is there anything I haven't considered here? Any thought or ideas would be welcome.
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Postby SteveH » Fri Jan 21, 2005 1:36 pm

Tom,

IMHO based on the amount of current drain you are talking about, it will work just fine. The obvious draw backs are the possibility of draining the tow vehicle's battery to the point it won't start the engine and the tow vehicle must be there and hooked up to the tear for the tear to have lights.

Years ago I had a slide in truck camper which had lots more current drain than what you are talking about and I had no problems camping for a few nights at a time with only the truck's normal battery.

Something you might consider is carrying one of those emergeny starting battey/systems in you vehicle.
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Postby Woody » Fri Jan 21, 2005 2:37 pm

You can buy a cheap small garden tractor or motorcycle battery at Walmart and install it in or on the trailer somwhere. Then use the tow vehicle to charge it when needed. Eliminating the potential for driving off and forcibly removing your umbilical when you forget to unplug it. For the current draw you mentioned it would work I think well. Just a thought
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One thing to think about

Postby Guy » Fri Jan 21, 2005 6:42 pm

Dear Tom,

All the above suggestions will work.

The only reason I can think for not doing it is that if you are running your car when you feel like the battery is depleting, then you will be creating a lot of unnecessary noise for the rest of us. This is especially true when you say Money is no object.
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Postby TomS » Fri Jan 21, 2005 8:36 pm

Guy writes:

The only reason I can think for not doing it is that if you are running your car when you feel like the battery is depleting, then you will be creating a lot of unnecessary noise for the rest of us. This is especially true when you say Money is no object.


If money were no object, I'd buy a larger tow vehicle, something really obnoxious, a Hummer perhaps.

But, alas, I live in the real world with one kid about to finish college and her younger brother about to start. A new SUV is not in the cards. I need to make my present car last. That is why I'm looking to save weight wherever possible.

I don't think noise will be an issue. My car idles very quietly. The only situation I can think of where we'd run the cabin lights for extended periods would be rainy nights. In that situation, the ambient noise from the rain would mask the engine noise.

Also, my remote starter automatically shuts the car off after 20 minutes if the key isn’t inserted into the ignition. So even if we fell asleep before shutting off the car, it wouldn’t run all night.
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Postby Chuck Craven » Fri Jan 21, 2005 9:17 pm

Tom there is another way! Add a second “deep cycle” battery to the toe vehicle with a battery isolator to the cars charging circuit.
Then run the tear off the second battery. If you kill the battery it will get charged from the car but it will not kill the cars battery so the
car will still start. Then the tear still has a deep cycle battery and the car will charge it if the tear is connected or not and all the battery weight is still in the car.
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Postby TomS » Fri Jan 21, 2005 10:59 pm

Chuck writes:

Tom there is another way! Add a second “deep cycle” battery to the toe vehicle with a battery isolator to the cars charging circuit.
Then run the tear off the second battery. If you kill the battery it will get charged from the car but it will not kill the cars battery so the
car will still start. Then the tear still has a deep cycle battery and the car will charge it if the tear is connected or not and all the battery weight is still in the car.


The question that comes to my mind is where and how to mount the deep cycle battery in the car? It would obviously have to be under the hood. The engine compartment is very compact. I don't know if I could make it fit. Seeing as how it's -3 deg F. outside right now, I'll wait till tomorrow to run outside and look under the hood.

Following up on Steve's suggestion, I found this emergency starting system on the HF web site

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=91045

It's got a 12 AH battery and weighs only 12 Lbs. I could either use as backup to jump start my car's battery if I accidentally drain it down. Or I could use it as the primary power source for the trailer. It also functions as a 12V power supply if I find myself at a campsite with AC power.
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Postby Chuck Craven » Sat Jan 22, 2005 12:08 am

It doesn’t have to be a big battery. You seem to have the power consumption down to a minimum.
A 50-amp hour or smaller battery may work for your needs. :shock:
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Postby David Grason » Sat Jan 22, 2005 2:14 am

I think it's interesting how the availability of newer technology makes us somehow feel that we can't ever go back to the way things used to be. Just think! Back in the old days when teardrops were new, no one ever thought anything about running interior lights for a time off of the car's battery. My dad said he and mom used to park the car on a hill so that they could read a little longer before turning in. It was a rare occasion that they ever had to bump start the car but it was always "just in case."

On another subject almost, I wonder if having a remote starter to recharge the car's battery while you were still inside the teardrop would create a dangerous situation with the presence of carbon monoxide in the trailer?
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Battery Backup

Postby Guy » Sat Jan 22, 2005 1:35 pm

Tom,

I bought one of those "jump starter" batteries in November in Mass. at a Costco. It was about thirty dollars. Had Battery Cables, AC and DC plugs, a built in air compressor for tires, a flashlight,and a voltage meter.

While I was driving back to California my cigarette lighter shorted and the jump starter kept my cel phone and computer charged for the next seven days. It also jump started a strangers car outside of ElPaso.

Wla-Mat also had them
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Postby TomS » Sat Jan 22, 2005 5:31 pm

Dave writes:

On another subject almost, I wonder if having a remote starter to recharge the car's battery while you were still inside the teardrop would create a dangerous situation with the presence of carbon monoxide in the trailer?


I was planning to connect the the trailer to the car with 15 to 20 foot cable. The car won't be so close that CO buildup will be an issue.

I'm more concerned with the prospect driving off with the power cable still connected to the trailer. I can be forgetfull sometimes. I was thinking of building my cable with male and female cigeratte lighter plugs that will separate should I drive off while connected. Either that, or I could connect the power cable directly to the battery with alagator clips. That way, I'll be forced to leave the hood up while the trailer is connected to the battery. The raised hood will serve as a visual reminder that I neeed to disconnect before driving off.
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Postby SteveH » Sat Jan 22, 2005 5:46 pm

Tom,

If you are going to use that much cable, it needs to be large guage wire...maybe 10 guage. :shock:
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Postby TomS » Sat Jan 22, 2005 7:48 pm

I made a quick inentory of the power consumption of the electrical devices I plan to install inside my tear.

13W round flourescent light. .8 amps

Brass LED reading lights 90 ma x 2 = .180 amps

Roof vent fan 3 amps (on hight)

If run all three of these devices at once, my maximum draw will be 3.98 amps.
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Postby mikeschn » Sat Jan 22, 2005 7:55 pm

So if you burn up 16 amps a day, you'll only need to hook up the teardrop to the car for charging once every few days...

Of course you could always go solar. Then, with a big enough panel, you could live in your teardrop indefinitely! :lol:

Now there's a thought for you!!!

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Re: Running the trailer off the tow vehicle battery

Postby bdosborn » Sun Jan 23, 2005 2:06 am

TomS wrote:I'd like to save weight anywhere I can since I have a small tow vehicle (Toytota Rav/4). If get rid of that big o'l box of lead 'n' acid, I can save 50 or 60 pounds off the weight of my tear.


Tom,

My truck has two start batteries in it and I still plan to use another battery for the trailer. I'm thinking it gets down to where you plan on camping. All it takes is one night of oops I left everything on to drain the start battery. If you're in the middle of BFE, how long will it be before you can get a jump? I camped in the back of my truck using the start batteries for lights and the laptop and I couldn't stop worrying about draining the batteries. I think a lawn mower or "jump start" battery would be good just for the peace of mind at a minimal increase in weight.
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