Looking for some electrical insight

[Robbie]

Hi all, I’m getting ready to start construction on my modified benroy teardrop and am trying to tie up the last bit of electrical knowledge I’ll need in order to have a super simple A/C setup, in case we ever camped at a campground, and also a fairly simple D/C setup for when were out in the desert or in the mountains. Some quick background, we don’t usually camp for more than 3 or 4 days. We don’t need a lot of electricity as we mostly cook over the fire and are outside by the fire or out goofing off and drinking so we won’t be in the trailer for much more than sleeping and getting out of the elements. I plan to wire the trailer similar to Joanne’s diagram in this thread.

http://tnttt.com/viewtopic.php?t=1941

Except my 12v system will only be running (2) 12v outlets for cell phone/ipod chargers, our portable DVD player, or a fan for the warm nights, a single interior dome light, an exterior porch light, and a rear cabinet light (not all at the same time obviously). So not much is gonna be drawing off the 12v system. I am planning on running some 8 gauge wires from the TV battery (Subaru Outback) to the trailer battery so it can get a charge while I’m pulling it. My biggest concern is running out of battery power and recharging it. I think eventually I will pick up a harbor freight solar recharging kit to keep in the trailer for day use but if we run a fan all night (fan-tastic for example, not the vent one) will 8-10 hours of continuous fan use drain the battery? What about with 2 hours of portable DVD player use and some lights use all mixed in? If the battery does die can I just hook up the charging wires and start my car and let it charge for a while off my Subaru? How long would that take for a full charge? I’m still not sure what kind of battery I should get and what Amp/hours are or any of that stuff (so some battery insight would be helpful). I just don’t want to build a system that is gonna be worthless.

Any and all help/criticism/bashing is welcome as I’m still trying to learn all this electrical stuff. Thanks.

Robbie

[Shadow Catcher]

A number of things.
You need to monitor your battery.
You can reduce load by using LED's and computer case fans. This may be sufficient to last three or more days.
You can use your Subaru to recharge your battery efficiently by using jumper cables (full output of the alternator) and monitoring the battery. Remember to kill the running lights pull up on the parking brake one notch. They need to be good cables with good clamps.
Harbor Freight solar is poor cost per watt and you can do better and have a controller that works.
three speed Antec case fans 100CFM on high each

[bobhenry]

You said super simple.......

Toss in a decent deep cycle battery and monitor with a voltmeter. At 10.5 to 11 volts start the car and wait for 12.5 to shut it off. With the items you are running the battery should last several hours of continuious use and as you will be flipping light and such on and off I would be surprised if this simple combo would not last 24 -36 hours of camping without the car recharge.

P.S. Since you are wired thru the harness you would be able to forget the jumper cables Tom mentioned, I think he missed that part of your post.

P.S.S. Be sure and report your findings if you run this way so other will know it can be done simple and easy !

[absolutsnwbrdr]

My teardrop has been "finished" for more than year and I still haven't bought a battery for it. Whenever I'm camping away from power, I have my trailer hooked up to my Subaru's battery, just as you have mentioned. I can run the Fan-tastic fan on high all night, have my LED lights on, and the car still starts in the morning.

The fan pulls 3.0 amps on high, and all of my LEDs' (interior and exterior) only draw about .4 amps.

If I do need any A/C power (for a radio or such), I have a small 400w inverter which has a built in low voltage shutoff.

If I'm in an area that power is available, I just plug in an extension cord that goes into my tongue box. Inside the tongue box, the extension cord goes to a 3-way adapter that splits the power to my 12v/5a Battery Tender, the rest of my 120V AC outlets in the trailer, and still leaves me with an open outlet in the tongue box.. Since I don't have a battery in the teardrop, the Battery Tender simply works as a 5 amp DC power supply.

All of my AC wiring is just hacked up extension cords.

The wires for my LEDs and fan is just 12 gauge speaker wire.

I'm still in the process of drawing up a diagram for my setup. Hope that makes a little sense.

[Robbie]

That is all very helpful info!

Zach,
You run your TD right off your subaru battery? I never thought of that. Could you post some pics of your electrical compartment for me as reference? Thanks. This might actually be a good solution for me until I can afford some decent batteries and expand my electrical system a bit. As far as connecting those power/ground wires to the interior trailer wiring, can I just add some connectors to the ends of the trailer harness and the power/ground wires and connect them directly where the battery would be? So this way when I get a battery I can just cut off the connectors from the interior trailer harness and hook it right up the battery terminals. I'll still use the master battery switch and the inline master fuse from the interior harness (like Joann shows in her diagram). What size should the master fuse be? 50 amps? 100 amps? I'm not sure how to figure that out. Also, the fuse that goes up by the TV battery in the + line? How big?

I'm still in the process of convincing my wife this whole idea is gonna be worthwhile. LOL. She is convinced we'll be sleeping in a coffin. So keeping the budget low and the inside comfortable is critical.

I did find some nice LED dome lights that I'll use to save some power. Probably the most power drawing item I'll have in the trailer will be the fan. I'm not sure yet if I want to save a little more and just get a fan-tastic vent w/ fan or build a setup like Shadow did and just build some hooks so the fans can hang under a static vent with a small plug for them to plug into. I guess I'll have to look into which setup will be best for all night use and cost effective.

I plan on running all the wiring in the trailer with 12 ga. speaker wire as it seems plenty big enough and can be found for pretty cheap. I'm gonna run 8 or 10 ga. wire for the power and ground from my Subaru's battery back to the trailer with a outdoor 2 prong connector zip tied to the trailer harness so it's all right there.

One last thing, you guys say to monitor the trailer battery via a voltmeter when I'm charging it off the TV, but in some other posts I've read that the TV's voltage regulator will keep the trailer battery from being overcharged? I'm confused now. I'll obviously monitor the battery with a voltmeter to be safe but would the car overcharge the trailer battery if I let it go to long by mistake?

Sorry for the long post! You guys are really helpful!!!!! Thanks!!

[Shadow Catcher]

One of the problems with this using the battery from the tow vehicle is that it is not a deep cycle battery and is not made to be discharged as consistently and this will shorten its life. The other problem is starting the car with a discharged battery. There are AGM batteries that can be used as both a starting battery and power supply but obviously there are compromises made in their construction.

[Breezy13]

I ran an 400W Power converter from my subaru battery for a wedding party, ended up replacing my battery and alternator the next week. Might have just been too much for too long(few hours), but a costly mistake, the alternator was $200. Just something to consider if running more than LED's from your car.

Breezy

[absolutsnwbrdr]

I ran an 400W Power converter from my subaru battery for a wedding party, ended up replacing my battery and alternator the next week. Might have just been too much for too long(few hours), but a costly mistake, the alternator was $200. Just something to consider if running more than LED's from your car.

Breezy

An inverter wouldn't cause the alternator to go bad. You can discharge the battery too much, but that's why I mentioned an inverter with a low voltage cutoff.

[Robbie]

So could I get a new deep cycle battery for my subaru and then run the power and ground wires from that back to the trailer? Or does that still have the problem of discharging the battery to the point of my car not starting in the morning. I'm just thinking that talking the wife into me needing a new battery for my car will be much easier than buying a whole new battery just for the trailer. Are Optima batteries deep cycle? I'm gonna go look them up.

[absolutsnwbrdr]

Robbie:

Yeah, my teardrop is powered directly from my Subaru battery. At the hitch of the car, I have a 2-pole plug, like you mentioned. I ran a single 10 gauge wire from one pole of the plug to the positive terminal of the battery. About 6 inches from the battery, there is an inline ATC style fuse holder, with a 20 amp fuse. The other pole of the plug gets grounded to the chassis (a trailer hitch mounting bolt) with a short 10 gauge wire. This short ground wire is electrically connected to the negative terminal of the battery through the car chassis. You can run both positive and negative wires directly to the battery terminals, but its just a waste of wire.

At the coupler on the trailer, there is a matching plug that connects to the plug at the car's hitch. The wires on this plug go into the tongue box to two bolts that are through a piece of wood - one bolt for positive, one bolt for negative. These two bolts take the place of the terminals of a battery that I will eventually install.

Then I have a fuse block that is wired to these bolts. Everything that gets power is then connected to the terminals of the fuse block, and a common ground (which is the negative bolt).

Regarding charging the trailer battery while towing.... since the batteries will be connected in parallel (positive to positive, negative to negative) there should be no need to worry about overcharging. Just make sure both batteries have inline fuses near their positive terminals (within a foot or so).

Check out this thread from 2 years ago, about charging while towing.

http://tnttt.com/viewto ... ile+towing

[absolutsnwbrdr]

So could I get a new deep cycle battery for my subaru and then run the power and ground wires from that back to the trailer? Or does that still have the problem of discharging the battery to the point of my car not starting in the morning. I'm just thinking that talking the wife into me needing a new battery for my car will be much easier than buying a whole new battery just for the trailer. Are Optima batteries deep cycle? I'm gonna go look them up.

A car battery and RV battery are two different types: starter and deep cycle. A starter battery will give you massive amounts of electricity in a short burst, such as needed when starting a car. A deep cycle battery is designed to give more constant power over an extended period of time, and cannot produce that initial boost to start a vehicle.

Heres a good article about that...

http://solarcost.org/deep-cycle-battery.html

[Robbie]

Zach that is the perfect answer to what I was inquiring about!!! Thanks a bunch man!

I think I will follow in your footsteps with the wire setup. I made an aftermarket grounding kit for my Outback so I'm sure grounding to the hitch bolt will be plenty. I think my battery is going to be mounted at the rear of my trailer in the storage compartment. I don't have a galley but rather a flip down tailgate that is a rear storage area and creates a small shelf at your feet inside. I guess I'll just need some longer wire. Or I'll mess around with the wiring and try to get it all coming from the front. The extra storage in the rear would be nice! And thanks for the battery info. I had no idea.

[absolutsnwbrdr]

No problem! Glad I could help! Heres a picture of my setup, using the bolts as power-poles.



Just be sure to cover those bolts so something metallic can't bridge them. Mine are covered up with duct tape right now, and I'm just careful that whatever gets thrown on top of where they are isnt metal.

Just a word of caution... people have suggested not to put your battery in the sleeping area, because they do emit small amounts of gas that can be harmful. If you do decide to keep it in the teardrop, build, or buy, a small box around it, and vent it to the outside.

[Robbie]

Just a word of caution... people have suggested not to put your battery in the sleeping area, because they do emit small amounts of gas that can be harmful. If you do decide to keep it in the teardrop, build, or buy, a small box around it, and vent it to the outside.

It is not in the sleeping area of the teardrop. I have a seperated compartment that is accessible from the outside only with a small tailgate setup. I would post a cross section of my design but photobucket is blocked at my work. So it is completely seperated from the sleeping cabin. I do plan on putting 2 of those circular ~3" vents on the side of this comparment to help vent any gases. One at the top and one at the bottom. I'll try and get a pic posted of what I mean today. But thanks for the heads up!