plans and questions

Anything electric, AC or DC

plans and questions

Postby mariannf » Wed Mar 16, 2016 11:39 am

Hi all, I have been reading about and planning for the electrical system. Here are my initial thoughts and some resources I have found helpful. My intent is to keep this as simple as possible. i have some questions embedded and hope some of you won't mind giving advice. here is the link to my build journal: http://tnttt.com/viewtopic.php?f=50&t=64888

1. I anticipate having few AC 110-120 V needs. so all i am installing is an RV cable hatch. I will get a heavy duty outdoor extension cord. I got this one: http://www.ebay.com/itm/like/2313760559 ... noapp=true

i don't think it gets much simpler than this.

2. for the 12 volt DC system, i will have three loads:
- a cabin light (1 amp) http://www.ebay.com/itm/1-NEW-RV-LED-12 ... 1731836311
- a fantastic vent fan (less than 4 amps on high)
- a dual 12 volt usb port (3.1 amps): http://www.amazon.com/Waterproof-Motorc ... ge_o01_s00


For the 12 volt Dc system i will mount a deep cycle battery in a battery box in the tongue box. The fuse block and ground block will also be in the tongue box. I have read that if the fuse block is close in proximity to the battery then a master fuse is not needed. Do you agree or think this is true? If i get a bunch of different answers i will probably go with installing one.

The wire length for any of the three loads will be approximately 15-20 feet. as such i believe the wire gauge needed from each load to the fuse block is 14 gauge (see this thread viewtopic.php?t=11316&highlight= ), but to be on the safe side i will use 12 gauge. Do you see any problem with this?

Grounding the battery. i have seen a lot of differing opinions on this. However, with safety in mind it sounds like grounding to the trailer frame is advisable, so that's what I plan. I have question: if i ground the battery to the frame, i also have to have a negative wire running between the battery and the ground block for the loads correct?

I will buy a battery tender to charge the battery. if there is one you like please let me know.

Finally, because i haven't done this before I plan to have an electrician look at my work. i have kids going in this thing!

Here are some links to resources i found useful in learning about 12 volt.

12 volt in general;
http://www.backwoodshome.com/installing ... ar-system/
http://www.marxrv.com/12volt/12volt.htm
http://www.truckcampermagazine.com/camp ... -the-wire/
http://www.cheaprvliving.com/blog/basic ... t-fixture/
https://www.youtube.com/watch?v=jHjmOJIlcdc

Example of wiring plan:
This is Joanne's...she has a thread in the all thing electrical forum here as well:
http://www.asolidfoundation.com/dd_electrical_1.shtml
http://tnttt.com/viewtopic.php?t=1317

a little about everything:
viewtopic.php?t=11272
Last edited by mariannf on Wed May 25, 2016 4:28 pm, edited 1 time in total.
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Re: plans and questions

Postby H.A. » Wed Mar 16, 2016 12:39 pm

I.
Last edited by H.A. on Sat May 14, 2016 5:26 pm, edited 1 time in total.
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Re: plans and questions

Postby MtnDon » Wed Mar 16, 2016 1:17 pm

Some will think I'm being too picky, but I believe that fuses and breakers do not belong in the same physical air space as non-sealed lead acid batteries. Given the right, or wrong, situation a fuse blowing or a breaker tripping can produce a spark which could ignite hydrogen gas.
Our 6x12 deep vee nose cargo trailer camper conversion... viewtopic.php?f=42&t=58336

We have a small off grid cabin we built ourselves in the NM mountains; small PV solar system; 624 watts PV, Outback CC & inverter/charger ... http://countryplans.com/smf/index.php?topic=2335.0
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Re: plans and questions

Postby troubleScottie » Wed Mar 16, 2016 2:58 pm

A master switch is always a good idea. It allows for disconnecting the battery from everything while in storage or traveling assuming nothing needs to be on. A big fuse on the battery (positive terminal) is also a good plan.

The battery tender may not be the best choice. You might want to consider a better multi-stage charger. Also, the charger needs AC. You need a way to get power to and into the tongue box. You can run wires from the cabin into the tongue box through roof or under the floor/outside the trailer. You can of course have two inlets -- one in the trailer and one in the tongue box.

I am not sure how many appropriate outlets a typical power pedestal has. Most likely you would be plugging into the same 15A wall socket. Not sure if that is good given the charger and whatever draws the AC is.

You might want to consider more lights -- just an led light is a bit spartan. Many people have overhead cabin light, two reading lights, two porch lights and a galley light. From a draw point of view, not a lot more draw because generally only one or two are on at the same time.

The only other consideration is switches to control them. Many light fixtures have a switch at the base, so another switch is not required. However a switch just inside the (either/both) door(s) or lower in the galley may be easier to reach.
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Re: plans and questions

Postby H.A. » Wed Mar 16, 2016 3:06 pm

What ?
Folks trapping explosive gasses inside a non ventilated enclosure ? Not using ignition protected OCPDs ?
SAE J1171 and ISO 8846 is known and understood by virtually everybody. I dunno...
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Re: plans and questions

Postby mariannf » Wed Mar 16, 2016 4:20 pm

MtnDon wrote:Some will think I'm being too picky, but I believe that fuses and breakers do not belong in the same physical air space as non-sealed lead acid batteries. Given the right, or wrong, situation a fuse blowing or a breaker tripping can produce a spark which could ignite hydrogen gas.


MtnDon, I am thinking of a sealed gel battery. does that address your concern?
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Re: plans and questions

Postby mariannf » Wed Mar 16, 2016 4:25 pm

H.A. wrote:If your distribution fuseblock is within the same enclosure, short distance to battery & minimal risk of something shortcircuiting to the battery, its fairly safe to omit a mainfuse.
Said that, a mainfuse or circuitbreaker still makes a handy method of main disconnect.

Grounded negative,
I think its good practice, really dont need to if all negative conductors are otherwise connected to the battery negative.


Hi there,
I want to make sure I get it; if i have all of the load negatives going to a ground block AND the battery negative is also attached to that ground block then there isn't a strong need to ground the battery to the frame?
Note...i probably will anyway but just want to get clear.

One more question; if i don't have a main fuse do I have to disconnect my battery from the loads when not in use so that it doesn't drain?
Thanks!
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Re: plans and questions

Postby H.A. » Wed Mar 16, 2016 5:35 pm

mariannf wrote:Hi there,
I want to make sure I get it; if i have all of the load negatives going to a ground block AND the battery negative is also attached to that ground block then there isn't a strong need to ground the battery to the frame?
Note...i probably will anyway but just want to get clear.

One more question; if i don't have a main fuse do I have to disconnect my battery from the loads when not in use so that it doesn't drain?
Thanks!


Yes you understand correctly.
Might add, If you plan to battery charge from the car, dont forget the grounding conductor of the trailer plug needs to connect to the battery as well. (The trailer plug positive charging conductor connects to your battery positive... [obvious] )

You dont have to disconnect your battery provided nothing in your trailer constantly draws power.
Some things what do constantly draw power are USB outlets, digital clocks, etc.
In general, even without these 'hidden loads', its not a bad idea to disconnect anyway.
Just be sure if you are using a battery maintainer/trickle charger, it remains connected.
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Re: plans and questions

Postby mariannf » Wed Mar 16, 2016 5:56 pm

Yes you understand correctly.
Might add, If you plan to battery charge from the car, dont forget the grounding conductor of the trailer plug needs to connect to the battery as well. (The trailer plug positive charging conductor connects to your battery positive... [obvious] )

You dont have to disconnect your battery provided nothing in your trailer constantly draws power.
Some things what do constantly draw power are USB outlets, digital clocks, etc.
In general, even without these 'hidden loads', its not a bad idea to disconnect anyway.
Just be sure if you are using a battery maintainer/trickle charger, it remains connected.[/quote]

Thanks H.A.
I was going to get a combo 12 volt outlet/usb outlet. maybe I won't. it isn't real important for me to have this. I mostly just want to be bale to charge a cell phone, and can do that through a 12v outlet (cigarette lighter) since i already have an adapter.

How do you diconnect a battery if you don't have a main shutoff?
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Re: plans and questions

Postby troubleScottie » Wed Mar 16, 2016 9:00 pm

You undo the wires from the battery. Technically either would work. Mostly people do the positive.

The big issue is reaching the battery. Depending on where it is, coverings, other equipment around it, accessing the bolt securing the battery cable can be a chore. Repeating the process to reattach can be a chore, especially if you remember as you arrive late at night on a rainy night.

In addition, a lot of battery posts will wear with repeated attaching/detaching (from my less affluent years with a poorly functioning car battery/charger system ).
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Re: plans and questions

Postby H.A. » Wed Mar 16, 2016 10:01 pm

Removing negative is safer as far as using wrench or whatever tool upon a battery terminal.
Fwiw,
Ojop makes a neat tool-less quickrelease battery connector. Fits post type battery terminals. Fairly inexpensive too...
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Re: plans and questions

Postby capnTelescope » Wed Mar 16, 2016 11:41 pm

I'll just comment on wire size, since no one else has. 12 ga is way more than enough. The only problem is expense. That said, 14 ga feels about right for the fantastic fan. 18 ga will work just fine for the lights.

Hey, it's only money.

:beer:
I'll burn that bridge when I come to it.

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Re: plans and questions

Postby mariannf » Thu Mar 17, 2016 10:42 am

Thanks you all, I really appreciate the advice!
Capn' I'll go with the 14 gauge on all.

H.A. thanks for the info on battery disconnect.
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