Learning and rethinking my cabin power system

Posted by Thomas Allen Schmidt on August 09, 2008, 02:40:41 PM

Re: Learning and rethinking my cabin power system (Reply #5)
If I may interject?
Did you know that the first electric lighting used in the White House was in 1891, during the Harrison administration? We all marvel at the Pyramids of ancient Egypt. More recently, at how this American nation gained its independence from Great Britain. All without utilizing the electricity we take for granted today.
Living "on grid," I think that we all would get accustom to using electricity how and when we feel like it, with no concerns as to, how much we use at one time. Living "off grid" can be like this, but at a great financial cost. In some ways I feel fortunate that I was able to live "off grid" with no electricity, what so ever, for a period of 20 years.
The very first item was electric lighting with 12 vdc 50 watt incandescent bulbs. Each evening when I got home, I would plug up the house to a cord hanging from the grill of my truck that was wired to its cranking battery. It took a while, about half year, but I eventually got a feel for how much and for how long I could "burn" lights and not have to push start my truck in the morning. This was in 1996 I think. Prior to that, I was reading the Mother Earth News by kerosene lamps, all the way back to 1975. I graduated high school in 1981. Prior to 1975, I was living the same "rubber stamp" life that millions of other kids my age where living. The change, for me, was like I had fallen off the edge of the Earth, and not just because of the lack of electricity.

Once again, fortune must have been smiling at me because the area I moved to, was then, a rural farming area and there was quite a few elderly people there that had spent their early childhood without electricity. I begged them to tell  me stories of how they grew up with out (before) electricity. For them, it was simple. They didn't know any other way.
 There is an old house at the end of my path, its abandoned now, but it still has the remnants of the original 30 amp 120 vac electric utilities service clinging onto it. A peek inside revealed 1 receptacle, and 1 light in each room. A flue pipe in the kitchen and a pitcher pump at the back door. The oughthouse had long since fallen back into the Earth where now is a large growth of Honeysuckle vines. The man that built this house as a young adult was one of those "kids" that I begged a story of his childhood from. He passed away about 18 years ago, at the age of 98. May he rest in peace.
This all brings me to a fact that a lot of people are not aware of. Electricity, as we know it today, is only about 100 years old. For well over 7,000 years there was no electricity for mankind to utilize. We people today are a living testament, to the fact that, mankind does not need the electricity we take for granted today, in order live out our time on the planet Earth. We merely want it.
So, I guess the advice I am trying to convey is re-evaluate your wants and needs where electricity is concerned, and you might find out, you could live with a lot less electricity than you think. Best wishes to you.
http://www.kountrylife.com/content/mem18.htm
« Last Edit: August 09, 2008, 02:48:48 PM by Thomas Allen Schmidt »
 

Posted by Thomas Allen Schmidt on August 09, 2008, 03:01:12 PM

Re: Learning and rethinking my cabin power system (Reply #6)
If, by chance, you havent laughed yourself silly at my notions, and are considering them, do a search, type in < life before electricity > and you can find a lot of pros and cons and just plain old enertaining stories. Such as,
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2005/06/19/RVG18D8F3E1.DTL&type=books
 

Posted by Ken Hall on August 09, 2008, 08:15:40 PM

Re: Learning and rethinking my cabin power system (Reply #7)
Jerry:

A single Xantrex C series controller is designed to function as a charge controller with PV Panels.  When you connect it to a wind or hydro generator, you set it to function as a diversion controller.  Attempting to use it as a charge controller from some other power supply usually will result in damaging one or more of the power supply, charge controller, or batteries.

I think you should use the Prosine regardless of the battery size and loads. If there is a difference in efficiency, it is only 1-2 percent while running. Your load estimate will have a larger error than that. They are essentially identical in standby, which is where they will be 90 plus percent of the time. The added features of the Prosine make it worth the small difference, if it exists.

The battery charging efficiency of the Prosine also needs to be considered. It was designed to be as efficient as possible on 15 amps input.  Many of the larger battery chargers out there, are less efficient if limited to a 15 amp input.

My bet would be that your total system efficiency (generator run time, power into batteries, and power out) will be better with the Prosine. For a MorningStar based system to come close, you are probably looking at a $400-$500 battery charger. 

You are right about installing the PV system before fall, if you leave the batteries at the cabin.  As long as you are making regular trips in for construction and fully charging the batteries before you leave, not having the PV should not hurt the batteries.  But if you find your time interval between trips starts stretching out, or you find that time before you leave doesn’t allow the full charge, that would also be signal to start hauling them home, until the PV is installed.

But meanwhile, I think you need to backup and re-think what you are doing here.  You started with the idea of a solar system.  You have the inverter/charger and a generator. You need the charge controller, PV panels, and batteries.

The price of the batteries to support a large microwave/toaster scared you. You are downsizing the solar. Meanwhile, the costs of an ac system that you did not originally mention are growing.

Your 3500 watt generator is going to be good for about 30 amps. Normally, this is phase A and phase B, good for 15 amps each. If one phase goes to charge the batteries, you are still limited to 15 amps for the kitchen. That will not run the microwave and toaster at the same time.  If you take both phases for large load use, you have to perform some type of switching, to bring the battery charger into play.  This will happen whether you build in a cabin wiring system, or if you just use two extension cords.

To support the battery charging, microwave and toaster at the same time, you will be buying a 4500-5000 watt remote start generator (or larger).  What do you think that will cost? What about the duplicate wiring, switch panels, etc., that you will need ?
I don’t think you have been looking at the costs of that.

I would toss the toaster. Use a non-electric stove top toaster. They are still available.  I would really give some thought to the microwave.  Just how much is it worth to you ??  Whether you put it on the solar system or an ac system, it is still costing you money.  The only way you can run it inexpensively is with the generator you have.  If your family really “needs” the microwave, electric toaster, hairdryers, etc, make them run an extension cord in the window, and pull the cord on the generator. They won’t get used nearly as much that way.

The way to get out least expensively is size your battery system for the lights, fan, tv.  Use the inverter that you already have.   Save a lot of dollars by not having two ac systems. Put a few of the dollars that you are saving into your battery bank/PV panels. If you size it at 450AH, it will support additional small loads easily.  Conversely, if your lighting/tv/fan estimate turns out to be on the low side, you may already be in trouble.  You will find it far easier to live within the 450 AH rather than the 225AH.


Ken
 

Posted by Jerry Wenzel on August 10, 2008, 10:23:43 PM

Re: Learning and rethinking my cabin power system (Reply #8)
Ken,

Thank you for your on-going support.  The Prosine does have a good charger, it is a fairly efficient inverter and I already have it, so should probably use it. It also has a "shore power" current limiting feature.  It monitors generator power consumption and backs off charging current if other loads, connected through the inverters transfer relay, need the power.

I never planned on running 2 appliances at once.  I just didn't want anything to get damaged if it did happen.  The Prosine can provide 2kW continuous and 4.5kW surge.  Now that I'm planning on using it, I was thinking about putting either a 10 to 15A breaker on the AC output of the inverter to limit it to providing 1200 or 1800 Watts.

Leaving the technical aspects and looking some more at why I'm putting in a system that could handle an appliance.  Our new cabin is going up next to a multi-family cabin that has its only electric light in the outhouse and no running water. 

Its clean but primitive.  I don't much mind it and can identify with your and Thomas Allen Schmidt's comments on simplicity.  However, the rest of my family, particularly my wife and daughters, like being at camp, but don't like the outhouse, lack of running water, inflexible gas lights etc.  Along with building the new cabin for more room for our family, another reason was to give it some more conveniences without going overboard.  I enjoyed this area as a kid and I'm trying to strike a balance in creating something my kids and grand kids will enjoy.

In using the Prosine, I'll need the beefed up DC power system.  But once its in, with the exception of a bigger battery bank, I should be set for the future.  A friend has some 350 MCM cable for me.  I need to see if I can get lugs crimped on the 350 MCM or look at buying prelugged 4/0 cables.  I'd like to post my DC cabling and protection for review once I come up with a design.

My first question regards to the DC system.

If I'm committed to limiting the inverter output to 15A or 176A DC ((15A*120VAC)/12VDC/0.85 eff) should I use a 200A fuse even if the inverter and DC cabling can handle 300A?

If I use a fuse instead of a breaker, do I need a disconnect and if so are there any suggestions on disconnect types.
 

Posted by Ken Hall on August 12, 2008, 11:36:44 AM

Re: Learning and rethinking my cabin power system (Reply #9)
Jerry:

Unless you plan on down sizing the wiring, I do not see any advantage to downsizing the fuse.

You need to use some type of disconnect upstream of the DC fuse.  The disconnect is located as close as reasonable to the positive battery post.  What that disconnect looks like probably depends on who is inspecting your work.  In many cases I’ve used a marine type battery switch.
http://store.altenergystore.com/Enclosures-Electrical-and-Safety/Miscellaneous-Electrical-Parts/Switches/DC-Switches/Blue-Seas-OnOff-Battery-Switch-300-Amp/p250/

I’ve also had  “Nervous Nellie Inspectors” insist on Industrial grade DC load break disconnects.  That gets a bit more expensive.

Ken
 
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