Electrial Pros - Please review my schematic.

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Electrial Pros - Please review my schematic.

Postby Capt. Home Slice » Sat Nov 21, 2009 11:38 am

As a relative novice to wiring, :? I've used the dissussions here to put together a proposed plan for my CT conversion. I'm sure there are some things that need adjusting so I'm looking for some guidance (which is much appreciated!) :bowdown:

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Postby Dale M. » Sat Nov 21, 2009 12:30 pm

Only issues I see is VOLTMETER..... It would appear you are running the voltage through it as same as same as ammeter..... A VOLT meter is wired across (bridging) the 12 volt line and ground..... Technically nothing goes through it....

Image

The above sketch is for a "automotive' (engine) application but the same "concepts" of wiring apply to your voltmeter circuit... Also you may want to put a push button or toggle switch in volt meter circuit so its not live all the time, although the "drain" from meter is minute, over a long time with trailer just sitting it will drain battery if trailer is not hooked to shore power and charger operational. And the is no need for it to be live when nobody is looking at it...

Also it appears that you have unlabeled fuses in ground circuit between "external power" and battery ... Schematic does not need this representation.....

Also for clarity, you may want to show "master buss bars" for 12 volts and ground, with fuses directly off them instead of taking the 3 battery(12volt) /ground circuits into battery box.... It really does not matter, because electrically its all the same......

Also a little magic with a relay could replace the rocker switch from manual control of battery charger (shore power) and TV charging.... But then again you may not want that feature automated...

Incidentally the Chev uses a 40 AMP fuse on the line going from fuse in engine compartment to trailer connector....

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Postby ARKPAT » Sat Nov 21, 2009 3:15 pm

As Dale said about some mods would make things automatic on plugging into shore power for charging the battery and inverter override ( depending on charger size rating ). Here below is a PAINT redraw of your circuit with the Volt Meter in the correct place.
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:thumbsup:

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Postby Capt. Home Slice » Sun Nov 22, 2009 9:45 am

Thank you for the replies. I understand how the voltmeter should be wired now. I'll make these changes as noted though I'm not sure I want to get into relays untill I've got the rest sorted in my head.. :crazy:

I have an additional question or two.. Let's take the charging ciruits out of the equasion for the time being and assume that for a 30A circuit a 10ga wire is needed.

After reviewing the power drawn from the inverter (if everything was in use) it adds up to 31A, so would I need an 8ga/50A wire/fuse in that circuit?

The wiring shown in the 4 bank fuse panel has power to an outlet, three lights and a Fantastic fan. The fuse #'s add up to 65A, but realistically it would be more like 20A for the power outlet, (using the max because this is a variable) and 6.8 for the lights and fan, for a total of 26.8A. At this time, this goes into one 10 ga/30A wire/fuse.

Assuming an 8ga/50A wire/fuse carrying 31A from the inverter to the master buss bars, and 26.8A from the power outlet, lights and fan to the master buss bars. If everyting was on at once, (a total of 57.8A) which probable won't happen though I want to play it safe, I'm not sure how to determine the size of the wire/master fuse that would go between the battery and the master buss bars.

It appears as though I would need a 60A master fuse using a 6ga wire from the battery to the master buss bars. Is this correct or do I have myself spun around?

I should also note that the distance from the battery to the location of the master buss bars will be about 7-10 feet.

Here is the visual to what I'm saying...
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Postby Dale M. » Sun Nov 22, 2009 10:55 am

New drawing looks pretty good....

Keep in mind advertises loads for devices are not always what unit actually draws. Usually they are less....

Keep in mind you will not be drawing maximum current to all devices all the time ....

As for wire gauge, except for main buss leads (battery to buss bars) you probably don't need anything larger than a 10 gauge...

Image

According to this chart, you can draw up to 50 amps a distance of 20 feet on a 10 gauge wire....

Keep in mind you can end up with "heavier" wire (weight wise) and more expensive wire (gauge) that application requires...

Its ok to over engineer, in fact in my work world before retirement the saying was "when doubt, go next size larger".... But the are limits to that thinking also....

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Postby Capt. Home Slice » Sun Nov 22, 2009 11:11 am

Thank you for the information, :applause: looks like I'm over engineering it a bit. :thinking: I'll redo the schematic, with wire length in mind (and a bit of a safety margin) using the chart as a guide.

Now, bringing the charging circuit back into play, is it ok to run that into the same fuse panel/ground bus as the other circuit? Would it be ok (and I think I read a thread on this subject but I don't remember..) to charge via either the TV or the battery charger while I'm drawing power from the battery?
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Postby Dale M. » Sun Nov 22, 2009 4:19 pm

Yes its ok to bring "charging circuits" to the buss bars (ground bar and fuse panel) shown on second sketches... Its just a common point where everything connects.... Its no different than taking charge leads direct to battery except it will go through the 60 amp fuse and amp meter..

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Looks OK in theory!

Postby eamarquardt » Sun Nov 22, 2009 6:37 pm

It's clear that you've put a lot of thought into planning your wiring. That, IMHO, is where a lot of the fun of doing it "your way" is! Enjoy the mental excercise. I know I do.

Here is a string I think you ought to read:

http://tnttt.com/viewto ... highlight=

Here is a primer on battery discharge:

http://www.batteryuniversity.com/print-partone-16.htm

Here is another good site:

http://www.schumacherproducts.com/applications/?id=0011

Based upon what I see, you are planning on drawing over 30 amps from your battery for extended periods (more than a few minutes at a time). I don't have any numbers to support my thoughts but in general you can only draw down half of the capacity of a battery before you need to recharge it. So, you have two hours max battery life at your expected draw. Not much, again IMHO. Drawing 30 amps from a 120 amp battery is too much to sustain for long and you won't even get the "rule of thumb" 50% of capacity due to the heat generated. In addition, the inverter isn't 100% efficient and effeciency varies with load. Finally, drawing your battery down frequently will greatly reduce its service life.

Following the guidelines on the Schumacher site it will take a long time to replace the energy you expect to draw from your battery. So, you'll need a lot of power, somehow (via ac charger, tow vehicle, or solar panels), to recharge your battery. More complications.

Why use an inverter at all. Going through multiple voltage conversions is not efficient. Why not use a 12 volt power supply for your computer, a 12 volt fan, a portable radio with 12V input, and a 12 volt charger for your phone. 12 volt doodads are usually designed to use less power (yeah they're not as powerful as 120 volt doodads but they can get the job done).

The "trick" to running on battery power is to minimize loads. No need for a gazillion watt stereo for some light casual listening in a campground (after all do your neighbors want to listen to your choice of programming). Use a small DC powered radio. Do you really need a fan? I leave my cell phone plugged into my car most of the time I'm out and about and have never even dented the car battery. Don't go through multiple conversions for the computer.


If you have commercial AC available, use it directly without going through the battery and inverter. Saves wear and tear on the battery and inverter. If you don't have AC available, work to minimize your DC load.

In short, keep it simple and minimize load. Crusing sailors have learned that doing without AC is much easier in the long run when away from the dock. When at the dock, use the AC as it comes from the plug, not AC to DC, and then DC back to AC.

Hope this helps. There you have it again, the world according to Gus.

Cheers,

Gus
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Postby Capt. Home Slice » Tue Nov 24, 2009 9:59 am

Hmmm.. another line of thought.. Thanks for the response, now you've got me thinking. ;)
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Postby Prem » Thu Dec 03, 2009 3:31 pm

Captain, and all,

I used to wire my big RVs for everything. Now I'm a Keep-It-Super-Simple minimalist.

West of the Rockies I don't need AC for an air conditioner (nights are cool, days are pleasantly hot at 2,500 - 6,000 ft.). I don't need to run a hairdryer, an inverter, a microwave oven or a TV / DVD player when camping. But if it's cold and I'm where I can plug in, there's an old-style, single plug, weather-proof electrical cover by the trailer tongue that lifts up exposing a hole a the wall that I can just slide an extension cord through. On the inside is the standard, RV, white plastic, exterior 120VAC access cover. I'll occasionally plug in a little electrical heater or hook my battery up to a charger.

All the interior is wired 12VDC with minimal draw LED lights. The battery is kept charged by panels when the sun shines. The system is basic. All four lines lead directly to the screw posts on the battery and each line has an inline fuse. The lines run in an exposed black plastic split tube. One goes up to the ceiling where it disappears to the solar panels on the roof and where one branches off to interior lights under paneling. I gave up on glamor and higher tech in favor of simplicity, ease of maintenance and low cost. I don't want DVDs, or satellite TV and Internet in the woods. Fishing and hiking are better. And Dutch ovens replace microwaves. Only inconsistency: I have a CC Radio with an external ferrite antenna that pulls in AM stations from a thousand miles away...and a CD player...both battery powered.

In my former teardrop, I put a power strip loose on the floor of the rear shelf and ran the male plug out just a little way through a hole in the corner of the wheel well. I caulked the hole and the cord with silicone, then cut a female plug off an old extension cord and used it as a cover to protect the male plug from road grime, sand and rocks. Worked great.

For my next teardrop build, I'm going even simpler. I have a heavy duty cigarette lighter (male) with heavy wire that branches to three female cigarette lighter plugs. I'll cut each of the three lines and put on inline fuses. Everything 12V will have a male cigarette lighter plug, even the ceiling lights. (I've spent too much time in Mexico.)

:coffee: Prem
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Postby kludge » Fri Dec 11, 2009 2:40 pm

ARKPAT wrote:Image



picture by Pat


1. On the charging circuit... the on-off-on switch, I assume that this will be wired so that only one charging source is connected at a time, right?

2. Also on the charging circuit... you can tie the two together on the other side of the 30A fuse and save yourself a fuse.

3. The way you have the amp meter wired, it won't see the current going to the inverter. Also do you want to see charge current or just discharge current?

4. I would prefer to see one cable going to each battery post from terminal blocks... i.e. all the 10GA wires go to terminal blocks, then one 4GA cable (or whatever size is appropriate) from the teminal blocks to the battery terminals. Makes for easier troublshooting, and connecting and disconnecting the battery.

5. 30A * 12V = 360Watts, not enough for a 400W inverter.
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Re: Schematic

Postby eamarquardt » Sun Jan 24, 2010 10:08 am

ronaldito wrote:You might want to take a look at my wiring, for some more Ideas


His schematic looks KISS (keep it simple stupid) and functional. Good work!

Cheers,

Gus
The opinions in this post are my own. My comments are directed to those that might like an alternative approach to those already espoused.There is the right way,the wrong way,the USMC way, your way, my way, and the highway.
"I'm impatient with stupidity. My people have learned to live without it." Klaatu-"The Day the Earth Stood Still"
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Fuses!

Postby eamarquardt » Sun Jan 24, 2010 11:05 pm

I got a bunch of 10 amp dc circuit breakers years ago at a place called C and H Sales. I plan on using them rather than fuses. You might consider checking around on the net for some and replace the fuses. If they are the lever type they can also serve as a switch. Not really designed for that but a friend has been using them for years on his Marine projects (he runs a business) and as Klatu said: "I find it works well enough to get me from one planet to another". If it works for years, it's good enough!

Just a thought.

Cheers,

Gus
The opinions in this post are my own. My comments are directed to those that might like an alternative approach to those already espoused.There is the right way,the wrong way,the USMC way, your way, my way, and the highway.
"I'm impatient with stupidity. My people have learned to live without it." Klaatu-"The Day the Earth Stood Still"
"You can't handle the truth!"-Jack Nicholson "A Few Good Men"
"Some people spend an entire lifetime wondering if they made a difference in the world. The Marines don't have that problem"-Ronald Reagan
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Postby Capt. Home Slice » Mon Jan 25, 2010 6:36 am

Thanks for all of the feedback and ideas folks. Once I finish tiling my bathroom (emergency project - ugh) :x I'm going to dig into the trailer stuff. :dancing
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