Mostly off-grid shed with AC safety net

[Oranjoose]

I couldn't decide whether to put this in the on grid or off grid sub forum, so let me know if this isn't in the right place. Figured the off-gridders have had to get a bit more resourceful .

To get to the crux of the question, I would like to have a system where there's a battery charger on AC hooked up to the batteries 24/7, but only keep the batteries at 80%. The solar panels would be responsible for pushing the charge above 80%. Therefore, the AC wouldn't kick in until the batteries dipped down to 80%.

The smart chargers available seem to be configured to keep the batteries topped off to the brim continuously (rather than the desired 80%). Does anyone know of an existing solution/equipment or clever DIY that I can deploy to achieve this? While there is intended to be a computer running 24/7 in this shed, I would like to avoid using computer controlled relays soldered onto existing meters/chargers to program this behavior.

A tiny more background is that I have the luxury of running AC to the shed 24/7, but I want to have solar contribute to the energy source. The shed is not supposed to use much power, but even so, I've calculated that going securely off the grid will be pricey. But going mostly off the grid, where AC can kick in on those stretches of cloudy days etc is significantly cheaper.

So my thought for doing this would be to have the solar panels connected to the battery bank with the charge controller as usual, and to simultaneously have the bank connected to the AC battery charger set to keep the batteries no lower than 80%. The computer electronics/lights would also be continuously drawing from the bank through an inverter.

Any ideas?

Thank you.

[Amy@altE]

Not sure what your budget is, but the Schneider SW inverter gives you a lot of programmable capability, including setting priority of PV over grid for charging the battery. Then you don't need a standalone AC charger. The Conext SW 2524 is under $1300.

[inetdog]

What I do not understand is why you have the batteries in the first place? Is the grid power so unreliable that you need the battery and inverter for regular use?

If you are normally operating all of the powered equipment in the shed off the inverter you are paying far more per kWh for your energy than if you just ran everything off the gird and configured your battery and inverter as a standby UPS instead.

More details please.....

[Bucho]

Is there a reason you don't want to use the power grid as your battery bank? I mean it's hard to beat a battery bank that's perfectly efficient and lasts forever.

[sdold]

Is there a reason you don't want to use the power grid as your battery bank? I mean it's hard to beat a battery bank that's perfectly efficient and lasts forever.

And costs 1/10th the money for power and is more environmentally-friendly

[Sunking]

One of the most silly things I have heard here. Last thing you would ever do let a Pb battery sit at 80% or every use battery power if you have commercial AC power available.

[organic farmer]

Where I live, the grid goes down at least once a month. Some months we lose power 3 or 4 times, for 2 or 3 days long each time. But most times the power is down for only 4 to 8 hours. Been here 9 years so far, so far no month has gone by without power lose.

We are going with Solar Power, as a method of hopefully getting access to reliable power. Meaning power every day, all month long, every month.

I want my 'off-grid' or grid-assist system to fully use solar power as much as possible, and at night to take a small charge from the grid [when the utility company manages to keep the grid up].

I hope that our battery-bank will be able to avoid cycling, and therefore to last longer.


In our town, most homesteads do not have access to the grid. We have one paved road going through town, power lines run alongside the road, but only for a part of the road, not all of it. 'Rural Electrification' in the 1970s did wonders for the Tennessee Valley, but they never got around to doing rural Maine.

The majority of towns in Maine, do not have grid power. When I was shopping for a home here, for most of the homes I looked at, the nearest power was 10+ miles away.

[organic farmer]

And costs 1/10th the money for power ...

The grid may be cheaper, but the grid only works on the days that the utility company decides the grid should be up. Otherwise, duh.

One of the most silly things I have heard here. Last thing you would ever do let a Pb battery sit at 80% or every use battery power if you have commercial AC power available.

It is silly to want power? Maybe it depends on how many days each month commercial power is available.



I think it is silly to make fun of people who want to be power for their homes.

[Oranjoose]

One of the most silly things I have heard here. Last thing you would ever do let a Pb battery sit at 80% or every use battery power if you have commercial AC power available.

I think it is silly to make fun of people who want to be power for their homes.

As I have been lurking, I have seen quite a bit of condescending the sunpeasants around here, actually. Maybe the hostility is coming from dealing with a new wave of hipsters, charlatans, and opportunists. I can see where spite would rise out of that.

More details please.....

Sure. I manage the shed as an on-site accessory to a group of people who need to access it. The shed has a couple led lights, very basic computer equipment to run a multi-camera surveillance system and a couple other sundry tasks, and air conditioning to keep the air around 50-60 F to properly store this type of equipment and supplies. The shed is insulated and approximately 6ft x 7f x 4ft in size. I live in Indiana.

The interest in solar emerges from a tenuous relationship between the landowner, from whom the electricity is drawn, and those who access the shed. I don't want to get into the details there, but we have a solid understanding that if we "supplement" the shed's power draws from solar, even if mostly superficial, the landowner will feel comfortable with our power arrangements (don't bother asking about just paying our share of the bill, fronting the cost we'd spend in solar toward the bill, or the like).

Based on what a couple of you have already said, I'm thinking that perhaps I could hook up the solar to take the computer and lights off the grid, and hook the cooling unit to the AC. I'm even considering alternative ways that I could cool the shed without using either solar or AC, but this is something I have yet to investigate.

The key here though, is that I want the shed's power needs to be as automated as possible, where I can check on it remotely or in person but once or twice a week, hence why I'm interested in some system that kicks in alternative power once the battery bank has hit a threshold. Amy@altE's suggestion sent me on a lead that resulted in finding something at least somewhat like this in order to set up such a system of backup power: http://www.solar-electric.com/schnei...tor-start.html .

Any other suggestions on this project are more than welcome. Thank you for the support!

[SunEagle]

The grid may be cheaper, but the grid only works on the days that the utility company decides the grid should be up. Otherwise, duh.





It is silly to want power? Maybe it depends on how many days each month commercial power is available.



I think it is silly to make fun of people who want to be power for their homes.

What I find a little disturbing is that this is the 21st century and that there are a lot of places in the US that does not have grid power.

If that is where you want to live then I would think whatever it costs to generate your own power is worth it to you.

[Bucho]

The grid may be cheaper, but the grid only works on the days that the utility company decides the grid should be up. Otherwise, duh.

Well that would be a reason, what your asking about is called a hybrid inverter: http://en.wikipedia.org/wiki/Intelli...ybrid_inverter

Amy already suggested one to you: http://www.altestore.com/store/Inver...Fdg8gQodzpsAUA

[organic farmer]

What I find a little disturbing is that this is the 21st century and that there are a lot of places in the US that does not have grid power.

If that is where you want to live then I would think whatever it costs to generate your own power is worth it to you.

If every square-mile of land in the USA were drawn on a map. I suspect that the overwhelming majority of them are uninhabited.

Most of the USA is rural [meaning less then 10 people per square-mile].

My town has a cellphone repeater, because the interstate goes through our town. But towns to our East and West do not. Most towns in this state do not have cellphone towers. Cellphones generally only work along the interstate, or else in cities.

It is not profitable to setup towers and infrastructure for zero customers.

That is why my town does not have any cable company, when homes are over a mile apart, you would need to string a lot of cable before you got 10 customers.

The economics work different in a city. When you can have 100,000 customers all within a single square-mile, then you can make lots of profit from stuff like that.

The power line in our town, goes through another 30 towns after. 92% of this state of forest. That is a lot of power line on poles shorter than the forest that over-shadows on both sides on the road. When one tree blows down in a storm, you lose power to 30 towns [or more].

Due to government subsidy the utility companies stay in business. But only because of the government subsidy.



I like rural. I moved here after I retired. It is peaceful. I can shoot a rifle in any direction from my house, and it is safe. Deer, bear, turkey are all harvested from on my land every year. Some years a moose is also harvested. We harvest more deer in a year, in our town, then we have residents.

Land prices are low, home prices are low, taxes are low, Cost-Of-Living is low.

Some of us like it this way.

[organic farmer]

Well that would be a reason, what your asking about is called a hybrid inverter: http://en.wikipedia.org/wiki/Intelli...ybrid_inverter

Amy already suggested one to you: http://www.altestore.com/store/Inver...Fdg8gQodzpsAUA

???

I am not asking for anything.

[J.P.M.]

What I find a little disturbing is that this is the 21st century and that there are a lot of places in the US that does not have grid power.

If that is where you want to live then I would think whatever it costs to generate your own power is worth it to you.

Yea, I thought that's what the Rural Electrification Program started in the '30's was all about. I guess the TVA/Grand Coolee/etc. lessons didn't get to some parts of the country.

[peakbagger]

If you look at night sky shots of northern New England, there is a distinct lack of lighting along a swath of the US Canadian Border from Lake Champlain east to Fort Kent Maine and then south along the border down to the Atlantic ocean. There are a few towns at key border crossings but its mostly farming in VT and treefarming east of that. About 1/4 of maine, the northwest quadrant is industrial timberland with some wilderness parcels. There literally are no public roads to the access the area. There is a large private road system to access the area but access is up to the owners. There is also another large block of timber and conservation land east of a line running from Acadia National Park roughly north to I95 in Millinocket. Much of the land was never populated and the townships have no names and are referred to by township number (T4 R5 WELS). Thus there is no reason to run power into the regions. There are some private inholdings at the fringe of the timberland and it is popular for homesteading and those who want to get away from the crowds. I 95 was built as a defense highway to service air force bases in Limestone and Bangor Me and also as way of trying to tie the state together. It has a very low volume of traffic but allows someone to be able to live out in the woods while still accessing services. Many folks routinely drive 60 miles one way to go shopping. For every homesteader that buys a place in rural Maine there are probably 10 who tried and went back home. The winters are long and summers are short. Power is significant issue in the winter.

OTG in rural maine sounds cool but the reality is there can be week long periods in the winter where there are no clear days. These stretches can last 4 to 8 weeks generally from November to January. Some try small wind as usually the wind is blowing when the sun is not out but small wind is notorious for poor reliability. I drive by many dead wind turbines while roaming the back woods. Even if there is power, the utilities maintain the lines to a bare minimum and when there is a weather event if may be days before power is restored. Thus if someone choses to live in the backwoods in northern new England, their thinking will be quite foreign to most folks. There are various books about moving to the backwoods and there is usually a chapter on the trade off between cheap land and the lack of power. Generally most authors admit that any savings in land cost is substantially offset by the cost to supply power on a year round basis. Not many homesteading folks have the 30 to 50 K that reasonably may be needed to provide a robust system, so many of the OTG systems are built up out of orphan parts over the years. This works if the owner has the smarts to do it right but many systems are an accident waiting to happen and if the original assembler of the system is out of the picture due to death, divorce or just plain giving up, the systems rarely survive another owner and end up in Uncle Henry's ( a local newsprint based craigslist) to get recycled again into some other kludged up system.

The other key point to consider is that many of the homesteaders are contrary by nature and don't take advice well. They are used to doing it their own way. An extreme example are the doomsday preppers on TV, no matter how suspect their theories of disaster are, they have made up their mind and are merrily heading off on their own path and hopefully no one gets in their way.