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12-16-2008, 07:42 AM   #16
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Do not run a low voltage circuit that far (with the transformer back at the house). The effects of voltage drop on 12 or 24 volts are much more severe compared with on 120 or 240 volts.

For a given number of amperes and a given piece of wire you lose the same number of volts, not the same percentage of voltage!

(Voltage drop within the cable equals number of amperes times resistance of the cable, remember it's a round trip.)

Last edited by AllanJ; 12-16-2008 at 07:44 AM.

 12-16-2008, 08:15 AM #17 Electrical Contractor     Join Date: Jun 2004 Location: Newnan GA Posts: 7,027 Rewards Points: 650 Battery, inverter, and a solar charger is what I would use. Or just use the battery and charger to power some 12 volt lights. __________________ "The problem isn't that Hillary Clinton lies. We all know she lies. The problem is that her supporters don't seem to care"
 12-16-2008, 08:53 AM #18 Member   Join Date: Jul 2008 Location: NW of D.C. Posts: 5,990 Rewards Points: 2,000 If it's for intermittent use, you can run skinny wires out there that would charge batteries, and then the batteries would run a DC-120vac invertor, or just run your stuff on 12vdc. 400w for 8 hrs = 3200 w-h of energy = 270 A-h of charge, at 12v. For the energy you put into the battery you'll get about 5/8ths back out again. You charge for 16 hours and then discharge for 8 hr. The batteries need about 14v at the terminals to charge properly. The voltage drop in the wires isn't important in this case because they are only carrying charging current and this is sort-of a constant current charging, but for safety I wouldn't have more than 60vdc at the sending end (the house). Depending on the charger you get, you may have to run the two leads to carry charging current and two very skinny sense leads http://digital.ni.com/public.nsf/all...2571D800712302 that monitor the battery voltage at the terminals. If you have a spreadsheet you can run the cost and energy budget numbers and see if there is a clear winner over running line voltage out there. Prolly there is no NEC involvement with the battery arrangement. Last edited by Yoyizit; 12-16-2008 at 09:37 AM.

 12-16-2008, 11:32 AM #19 Member   Join Date: Jun 2007 Posts: 3,793 Rewards Points: 246 As said above you must install a breaker in your main panel or another panel inside your house. From this breaker you can run UF cable underground to the tree house. Keep in mind you must protect the UF cable when it comes up out of the ground and you MUST have a disconnecting means at the tree house. It must be GFCI protected. A simple snap switch will be just fine. Calculating a 5 amp load you would need #4 at 750 feet. #8 at 3 amps load will work too. This is at 3% max voltage drop. Note: If you are not familiar with any of my statements you really should call a professional electrician.
 12-16-2008, 12:05 PM #20 Member   Join Date: Jul 2007 Posts: 2,045 Rewards Points: 1,910 Hardwiring 120volts is going to set you back a grand at least -maybe quite a bit more. Now let's get realistic. This is for use mainly in the summer. When is sunset? 8:30 to 9PM? Just how late is Mom going to need those kids in the tree? You probably need an hour of light. Get a small solar panel and battery and low voltage lights. Save a lot of money and make Al Gore proud.
12-16-2008, 01:10 PM   #21
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## options

Charger-cable-battery-invertor
120vac-cable-120vac
240vac-cable-step down xformer
solar

One minimizes fixed costs, another recurring costs, another payback period.

 12-16-2008, 01:11 PM #22 Member   Join Date: Nov 2007 Location: Nashua, NH, USA Posts: 7,971 Rewards Points: 1,548 Running low battery-charging-only voltage from a battery charger back at the house is not going to work well except for very feeble trickle chargers. Otherwise as the battery charges up, the current draw will vary enough to make the voltage applied to the battery vary all over the map. Last edited by AllanJ; 12-16-2008 at 04:35 PM.
12-16-2008, 01:34 PM   #23
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Quote:
 Originally Posted by AllanJ Running low battery-charging-only voltage from a battery charger back at the house is not going to work well except for very feeble trickle chargers. Otherwise as the battery charges up, the current draw will vary enough to make the voltage vary all over the map.
I think you're right, for somewhat different reasons.

3200 w-h for 16 hours is 200w, which, at 12v or so, is high current over long wires, which defeats the purpose of going to a low-duty-cycle battery system.
And, a constant current charger is not going to work over about 4Adc because of what the batteries can tolerate. 4A over 16 hrs. is not enough A·h of charge for this application.

For the required amount of energy and peak power to be delivered I guess I'd go with 120vac or higher to minimize copper loss and wire size.

BTW, you might get 6w per sq. ft. of solar panel when the sun is shining, so this would be a panel about 8' on a side.

Last edited by Yoyizit; 12-16-2008 at 01:57 PM.

 12-16-2008, 01:52 PM #24 DIY'er     Join Date: Sep 2008 Location: Neenah, Wisconsin, USA Posts: 2,044 Rewards Points: 1,024 Blog Entries: 2 I think this is beyond what the OP is willing to do, but can you run a Buck/boost to compensate for voltage drop? i.e. send out 140v ac on a line and with voltage drop it ends up being 115ac when it gets there? Isn't this how the power co transmits power over long distances, higher voltage, using something like 17K-34K until it hits the transformer by your home then it is stepped down? Jamie __________________ Jamie Dolan - Neenah, WI Jamie Dolan Paw Dogs Need Help Uploading Photos? Click here.
12-16-2008, 02:03 PM   #25
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Quote:
 Originally Posted by jamiedolan I think this is beyond what the OP is willing to do, but can you run a Buck/boost to compensate for voltage drop? i.e. send out 140v ac on a line and with voltage drop it ends up being 115ac when it gets there? Isn't this how the power co transmits power over long distances, higher voltage, using something like 17K-34K until it hits the transformer by your home then it is stepped down? Jamie
You're kidding, right? A buck/boost transformer? Let's all get real here. Put a solar light in the thing and call it a day.

12-16-2008, 02:10 PM   #26
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Quote:
 Originally Posted by jerryh3 You're kidding, right? A buck/boost transformer? Let's all get real here. Put a solar light in the thing and call it a day.
I was asking because I was curious if it would work. I was under the impression they are not that expensive. I saw a bunch of used buck boot units for \$50.

I agree simple is the best solution. If they are willing to do solar or battery, go for it.

If the guy is thinking about spending the \$ on 750 of 8 gage wire, he must be prepared to put some money into the project. My thought was a run of 12 gage romex for direct burial, connected to a buck/boost right next to his panel. The cost difference between 12 and 8 would probably pay for the transformer and a electrican to install it. I just don't know if it could compensate enough for the voltage drop to make the power useable.

Jamie
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 12-16-2008, 02:49 PM #27 Newbie   Join Date: Dec 2008 Posts: 8 Rewards Points: 10 great help everybody! I think I will talk to a local electrician about everything since I definitely do not want to get hurt doing this. About the solar panels as a few people have mentioned, they seem to be more expensive then doing this project. How much would a battery, inverter, and solar charger cost? And how much juice could I get from it?
12-16-2008, 03:00 PM   #28
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Quote:
 Originally Posted by needshelp great help everybody! I think I will talk to a local electrician about everything since I definitely do not want to get hurt doing this. About the solar panels as a few people have mentioned, they seem to be more expensive then doing this project. How much would a battery, inverter, and solar charger cost? And how much juice could I get from it?
I have a 400 watt inverter(cost about \$50), a trolling motor battery(\$80),
and a trickle charge soler charger(\$30) and that powers my battery chargers, a radio, and a small fan most of the day.
If you go this route, you need a deep cell battery.

You may have to deep charge the battery every month or so.
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12-16-2008, 03:13 PM   #29
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Quote:
 Originally Posted by jbfan I have a 400 watt inverter(cost about \$50), a trolling motor battery(\$80), and a trickle charge soler charger(\$30) and that powers my battery chargers, a radio, and a small fan most of the day. If you go this route, you need a deep cell battery. You may have to deep charge the battery every month or so.
That all sounds great. What about the solar panel? where can I buy all the items you mentioned? I'm assuming Home Depot does not carry such items....

12-16-2008, 03:20 PM   #30
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Quote:
 Originally Posted by needshelp That all sounds great. What about the solar panel? where can I buy all the items you mentioned? I'm assuming Home Depot does not carry such items....
Harborfreight has some solar panels, I don't know much about them. They have some inverters as well.

Jamie

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