12v for the Minimalist Weekender

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Re: 12v for the Minimalist Weekender

Postby tony.latham » Sat Oct 05, 2019 9:22 am

This makes perfect sense. Instinct tells me you cant run a fan all night on a battery.


Where are you planning on camping? I've never had my fan run for more than an hour. And that was for a nap during the heat of the day in Montana.

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Re: 12v for the Minimalist Weekender

Postby Tom&Shelly » Sat Oct 05, 2019 9:56 am

MtnDon wrote:
tony.latham wrote:....When you get your fan and probably the lights, black is positive and white is ground......


Actually, to me, that makes total sense, comparing house wiring where black is the hot wire and white is called the neutral. (There is also a ground that is bare or green when insulated.) Looking at it that way, the AC wiring black wire corresponds to the DC system positive, also thought of as a hot wire. The AC system white then corresponds to the DC system white, which I call the negative wire. Some folks call it a ground wire, but it really the negative as it is connected to the negative battery terminal. :)


That is a good way to look at it, but it reminds me of a story. (At my age, everything reminds me of a story! :roll:) Back in the mid-1980's, as a US Air Force 2nd lieutenant, I was stationed at a communications site in England. The British 240 v/50 Hz wiring system is brown = line, blue = neutral, and green/yellow = ground. But they had updated their code at some point after World War II, and their pre-war wiring system was red = line, black = neutral. Many of our buildings (lent to us by the RAF) still had the old wiring.

Now, occasionally, US communications systems were shipped along with US Romex for installation at the site. So what do the British electricians know of black = line, white = neutral? (The green = ground they could guess.) Often they assumed our black was the same as their old black, ie, neutral. Shocking as that may seem (and sometimes was!) :shock:

As I work on the wiring for our teardrop, slowly, in between non-teardrop related projects, I have some things that use white/black, some that use black/red, some zip cord that has one or more stripes on one side, and speaker wire with silver/copper color. Particularly with my memory and the gaps between work, I decided to put red = +12/black = neutral heat shrink at the intersections of the wires. Hopefully, that will prevent blowing a fuse or worse. I even went out and bought a bunch of colors of heat shrink for the trailer/TV wiring, to try and keep that straight.

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Re: 12v for the Minimalist Weekender

Postby twisted lines » Sat Oct 05, 2019 10:08 am

Tukanu wrote:This is good stuff,
Based on my rudimentary schematic:
Thanks for your input.


:thumbsup:
Nothing rude about it. But this may be?
Since your drawing is Very close to where I am heading if I may.

Power (110 AC) is already Inside, If one is wanting to add One outlet inside for a ceramic heater;
GFCI or NO; and would/should it be Grounded to the chassis.
Last edited by twisted lines on Sat Oct 05, 2019 10:52 am, edited 1 time in total.
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Re: 12v for the Minimalist Weekender

Postby tony.latham » Sat Oct 05, 2019 10:28 am

Power is already Inside If one is wanting to add One outlet inside for a ceramic heater;


A small 1500 watt ceramic heater will drain a battery fast. Minutes, depending on battery size. :frightened:

My first teardrop was commercially made. It had one of those little 150-watt dash-board heaters in it that I think was installed for marketing purposes. It put out close to zero heat and sucked 11 amps/hours. Ouch.

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Re: 12v for the Minimalist Weekender

Postby twisted lines » Sat Oct 05, 2019 10:53 am

tony.latham wrote:
Power is already Inside If one is wanting to add One outlet inside for a ceramic heater;


A small 1500 watt ceramic heater will drain a battery fast. Minutes, depending on battery size. :frightened:

My first teardrop was commercially made. It had one of those little 150-watt dash-board heaters in it that I think was installed for marketing purposes. It put out close to zero heat and sucked 11 amps/hours. Ouch.

Tony

Sorry tony fixed it, as the OPs map the power is in for the charger.
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Re: 12v for the Minimalist Weekender

Postby Tukanu » Sat Oct 05, 2019 11:04 am

You guys have got me rethinking my whole electrical plan. I think I am going to go with pre WW2 British 220 and move the electrical panel to the galley.
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Re: 12v for the Minimalist Weekender

Postby RJ Howell » Sat Oct 05, 2019 2:09 pm

[quote="tony.latham"]

Now... I modified the fan with a 4-ohm resistor to slow it down. The first number is the amp draw with the modification and the second without so that 3 amps is close.

Now that's probably beyond the OP, but I like! I didn't mis-state your a smart dude (also willing to experiment a bit). Me, I start with a potenciometer and dial in from there. Yet that's you and I.. :thumbsup:

If you drop the voltage below 12, you're damaging the battery as RJ said. This voltage needs to be read after at least a half-hour (better an hour) with no draw on it. (If it's indicating 12.6 volts and you turn the fan on, it may read something like 11.8. Ignore that. It needs to be read after the battery is at rest.)

To this I will disagree, yet within an hour you can see where it's headed. Standard is 24 hours for true reading. 12 hours (or overnight) gets you real close. To me the longer you let it rest the better the reading. I do believe best is to buy a meter like what I showed you and read the output. Then there's no guessing in this, you know!

Image


Several charts for SOC voltage out there. Mine and yours are slightly different, yet still keeps the battery within levels of performace.

/quote]
Last edited by RJ Howell on Sun Oct 06, 2019 6:34 am, edited 1 time in total.
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Re: 12v for the Minimalist Weekender

Postby Tom&Shelly » Sat Oct 05, 2019 3:26 pm

Tukanu wrote:You guys have got me rethinking my whole electrical plan. I think I am going to go with pre WW2 British 220 and move the electrical panel to the galley.


LOL! :lol: (But how did you get a picture of one of our electrical boxes?)
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Re: 12v for the Minimalist Weekender

Postby MtnDon » Sat Oct 05, 2019 4:10 pm

tony.latham wrote:Don: You've got me on that one. Maybe it was just me looking for an excuse to bash the RV industry. :?

Tony


Don't need an excuse for doing that :lol:
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Re: 12v for the Minimalist Weekender

Postby H.A. » Sun Oct 06, 2019 4:35 pm

black is positive and white is ground. That's the RV world being goofy. Go figure.
Thats goofy NEC requirement for grounded conductors.
Especially so for mixed systems.

The RV world is not goofy. Its far worse than that.
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Re: 12v for the Minimalist Weekender

Postby Shadow Catcher » Sun Oct 06, 2019 5:56 pm

The two things I will add, substitute a couple of 120 mm Antec three speed computer case fans, much less current draw. 79656
Plan on far more than you think you want, it is amazing how many outlets you can use and get a good size battery.
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Re: 12v for the Minimalist Weekender

Postby tony.latham » Sun Oct 06, 2019 5:58 pm

...goofy NEC requirement for grounded conductors.
I had no idea the NEC covered RVs. Or at least teardrops with a 12V system.


:thinking:

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Re: 12v for the Minimalist Weekender

Postby Az Pete » Sun Oct 06, 2019 6:56 pm

Tukanu wrote:Thanks. I looked at that one, but wasn't sure what it is telling me. When the volts drops to certain level, does it mean there isn't much juice left? What is the critical level?
I could go to 55 AH without much more cost.


I would go for a larger battery, just to have the reserve power. As batteries age, they loose capacity. Your demand is pretty low, but if you draw the battery down too much, it will likely kill it.
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Re: 12v for the Minimalist Weekender

Postby MtnDon » Sun Oct 06, 2019 7:41 pm

tony.latham wrote:
...goofy NEC requirement for grounded conductors.
I had no idea the NEC covered RVs. Or at least teardrops with a 12V system.


:thinking:

Tony

Article 551 defines (of the NEC) "recreational vehicle" as a vehicle-type unit used as temporary living quarters for recreational, camping, or travel use. The four basic entities are travel trailer, camping trailer, truck camper, and motor home [551.2].

Basically, the NEC does include all the AC wiring inside an RV. But it makes no mention of the DC apparatus. The RVIA has some rules too but IIRC it mostly copies from the NEC for all the AC stuff.

And I don't think there are any goofy aspects to the NEC, if one really looks at the NEC and thinks about what a "dumass" DIY might inflict on themselves and others. Mostly it is about safety and doing things one way so everybody should be on the same page. Makes service easier and safer "down the road" a few years.
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Re: 12v for the Minimalist Weekender

Postby tony.latham » Sun Oct 06, 2019 8:39 pm

And I don't think there are any goofy aspects to the NEC


I agree. Except for the 30 amp disconnect, I was just told the inspector was going to need to see on the side of my new garage. But that's a different story. :frightened:

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