off grid cabin/ home

wellbuilt · May 2014

Hi all , this is my first post !
Im starting a cabin/ house build to day .
I have grid power 1500 feet down on the road but don't really have money for blasting holes for poles running wire etc.
the cost is 35000 dollars +- .
Most of the time I run a generator to work , but we will need to live on site 3 days a week .

This will be a weekend getaway when finished , but I will move there in 10 years +- .
so I was thinking that battery / inverter power charged with a generator could be a option.
I was thinking I need to run 2 tools at @ time 1300 watts for 3 hours a day 4200watts + radio and 12 volt battery chargers lite .
If I need more power I could run the generator .

I was thinking (8x) interstate L16 @ 48 volts
magnum inverter 4448 or out back 3648 or what ever you guys think would be better .
The equipment would be used at the house as back when finished.
I will use wood heat , propane stove/ water heater/ frig.
I think the house will also end up being solar power one day since it seem like we are all heading in that direction.

Soooooooooooooooo If you could help me with a design plan for that all so .
The cabin will be 1300 sq feet with a 2 car garage The 2nd floor will be unfinished for now .
My roof points south and is 45o no shade we are @ 3200 feet at the top .
What size generator is needed to charge thru the inverter ?
what in the best place to buy equipment ?
Thank for the help in advance .

Cariboocoot · May 2014

Re: off grid cabin/ home

Welcome to the forum.

Well if grid install is going to cost $35,000 then off-grid looks quite attractive!

You've got a generator. Now you need a Kill-A-Watt meter. You put the two together and measure the loads you use while living there. This gives you an accurate number for power consumption. You need that before you buy any solar equipment. Otherwise you're guessing and spending money unwisely.

Planning the system to run two 1300 Watt tools at one time is probably a big mistake. You need to look at what you run on a regular day-to-day basis and consistently. The gen can do for the tools on an as-needed basis. Perhaps even a smaller, more efficient gen; it could be cheaper than investing in solar for occasional tool use.

A couple of years ago I reroofed my place. This involved using power tools including an air compressor for the nailer. The system was not design to power such, but by bulking the batteries early with the gen the panels could then take over and keep everything running 'til day was done. Much more economical than putting in another 1500 Watts capacity.

Forget about what you're thinking about until you figure out what you need. The things that matter are maximum Watts and daily Watt hours; that's what you'll be trying to supply.

mike95490 · May 2014

Re: off grid cabin/ home

Well if grid install is going to cost $35,000 then off-grid looks quite attractive!

If I could have put in power poles for $35K, I'd have done it in a heart beat. Starting from raw land, built generator shed, battery shed, pole mount PV array, batteries, inverter, was way over $35K (even before my new batteries)

Get the meter, find out your loads, and then price it out.

BB. · May 2014

Re: off grid cabin/ home

Just to give you some ideas:

500-1,000 Watt*Hours per day (0.5 to 1.0 kWH) is a "small" system (lights, laptop, small fan, LCD TV, small water pump)
3,300 WH per day (3.3 kWH) will support an Energy Star refrigerator, clothes washing machine, well pump--Near normal electric home--albeit very conservation minded
10 kWH per day (big system)--Typical very efficient north American home
33 kWH per day (bigger system than most people can afford for off grid)--Average north American home, no conservation (~1,000 kWH per month)
100 kWH per day (don't bother with pure off grid solar)--Living in Texas with full A/C, electric stove, hot water, etc.

And while utility power may cost around $0.10 to $0.20 per kWH, off grid power will cost you around $1 - $2+ per kWH. There are a few folks here that are towards $0.50 per kWH--But that is probably not the norm.

Running a genset, you will be spending around $1-$2+ per kWH just on fuel (generators will really suck fuel at less than 50% of rated load--Gasoline gensets will draw around 50% of rated fuel flow at 0-50% of rated load... The inverter-gensets from Honda and Yamaha are a bit more efficient at lighter loads, and a lot quieter).

So--If your electric bill was ~10x your present electrical bill "today"--What would you do different.

You can do much of what you want with a smaller off grid power system and small Honda/Yamaha for backup. And get a "cheap" / loud genset that you fire up when you are running your larger tools/air compressor.

It is certainly possible to run your major tools off solar power--But if it is short term/seasonal, typically a generator is going to be more cost effective.

Solar is better for "full time" loads (~9 months or more usage).

For example, weekend living would point to propane fridge as being a good deal. However, if you are running the fridge 9+ months a year, then an Energy Star rated refrigerator + a large enough solar power system to run it (3.3 kWH per day, around 1,600 watt array + 1,200 to 1,500 watt minimum AC inverter) will do very nicely. And a good quality backup genset+AC battery charger for the dark and stormy winter days (when needed). And such a system would probably run your skill saw (and smaller) hand tools very nicely.

-Bill

mike95490 · May 2014

Re: off grid cabin/ home

I would not trust generator as prime power unless it was Honda, or a commercial grade genset. Gotta cost over $150 per KW or you are buying disposable junk.

While building, you can do a lot of things. Tweak the roof for solar harvest. put in heavy rafters to carry weight of PV and Water heater panels. Add the plumbing inside out of the weather.....

And you can always install a couple panels for "camping use", and flesh out the full system later. (Unless you think you want them all there now)
Batteries age and die, in use or not. Maybe a very small bank, use it hard 20 x a year, and just replace cheap batteries 2x before you move in. Size the inverter/charger for your final loads. Consider inverter/charger with Generator Support (not the same thing as generator controls). Evaluate an auto-start generator. I'm tired of having to babysit the manual genset.

Have you mentioned water ? Well ? pumping ? what size motor ?

And if it's still under construction, I heartily endorse Masonry Heaters. http://www.mha-net.org/documents/what-is-a-masonry-heater

BB. · May 2014

Re: off grid cabin/ home

A Honda eu2000i costs around $1,000 on the Internet (delivered--a few years ago, may be more now).

A Honda em4000sx (make sure "sx", not "s" or similar--SX has full electronic engine control module, including mixture control for hacking into auto-start). Probably north of $2,000.

-Bill

jonr · May 2014

Re: off grid cabin/ home

Some solar is fine, but instead of a generator, how about a couple of small trailers loaded with batteries? Alternate which one is left down by the power pole for a nice complete charge.

Cariboocoot · May 2014

Re: off grid cabin/ home

jonr wrote: »

Some solar is fine, but instead of a generator, how about a couple of small trailers loaded with batteries? Alternate which one is left down by the power pole for a nice complete charge.

The utility and/or AHJ may not allow a 'remote' power installation even with a shed.
Or the lines in question may be on public land where a private meter would not be allowed (i.e. he needs to run these lines to his property first and there's the $35,000 cost).

wellbuilt · May 2014

Re: off grid cabin/ home

Thanks for the reply
Caribo , I would like to flood the net with a bunch of facts , spec, and , # but My cabin dosent exist yet .
I have no clue what equipment will be needed and don't have any thing to test on .
Based on my reading im thinking 3/4000 watts a day could work for my needs now and later .
The l 16 battery bank was picked because they are available to me, and they give me around 4500 watt hr per day discharge , with one days worth of power for back up .
My budget is tight if I spend on grid power now I will not have moneys to get the roof on this year .
I would like to be closed in by thanksgiving .
Im getting older and can still do a good days work , I have my sons to help me (now ).
I could just run a generator 16 hrs a day 50hr a week when we are working there but that would get old .
I did like the magnem inverter with generator support I think its 4000watt 24 volt I could run a 2 string bank.
I have a travel trailer in the works and it will be 12v Buuuuuuut it dosent help me if we have no power .
I could keep the inverter and battery bank in the trailer for now .
I will frame up the garage first and mount the equipment in side .
I need to make living there easy, so we can get more work done.
I wont know about the well pump till I have a well drilled , maybe next week, some wells are drilled 900 feet deep and have water 5' down some are 4/500 feet and the pumps are down 200' ?
I would say the pump would be 1 hp 240v ?
If my battery bank was a little large , or my inverter was a bit large , or there are a few more solar panels would it be a total was of money .

If we show up to work and there is no power we would have spent 250 dollars in fuel , would have bought breakfast on the way there, lunch on the way back , or I would be hunting for a new generator at lowes.
There must be something I can do .
You guys are the best thanks .

Plowman · May 2014

Re: off grid cabin/ home

wellbuilt wrote: »

so I was thinking that battery / inverter power charged with a generator could be a option.
I was thinking I need to run 2 tools at @ time 1300 watts for 3 hours a day 4200watts + radio and 12 volt battery chargers lite .
If I need more power I could run the generator .

I'm living in an off-grid RV, just 2 Trojan batts and 1 158W panel (soon to be 4 hopefully). Done a lot of small projects, framing an outhouse, building a water barrel rack, building a small deck, etc. Having to fire up the generator every time I wanted to drill a screw in got old so I recently got a cordless tool kit (Porter Cable). The cordless drill is great, the cordless circular saw and reciprocating saw are almost useless unless you just need to make a couple cuts or are cutting thin plywood. I use lithium ion Dewalt cordless drills at work and they are fantastic, long battery life, quick recharge, lots of power, but very expensive. I recharge my cordless tool batteries via my solar/battery system.

My 15-amp corded circular saw draws 1800W, more than I'd want to draw from my batts, plus inverters in that size get pricey real quick (not to mention having to have tree trunk sized wires to connect them to the battery). When I need to do a lot of cuts I just use the generator (Honda EB3500). I preplan and measure all the cuts I want to make so I'm not futzing around while the generator is running. I also usually charge my Trojans while the generator is running since my power tools only use about half the generator's capacity---either that or I keep it in Ecothrottle mode so it's not running full bore all the time.

I lived all winter just on my generator and a big AGM, running the generator for hours at a time got real old real fast, not to mention expensive. Which is why I'm expanding my solar electric system.

Sizing the generator really depends on how big your battery bank is. My EB3500 charges my two Trojan T-105s no problem. I use an Iota IQ4 45-amp battery charger. I suspect an EU1000 would probably work fine for my little system---they're ~$1000.

Eight L-16s @ 48V I have no idea, but I assume it's the same as 12V. 10-13% charge rate is what Trojan recommends, though I think (probably erroneously) that slightly more when charging from a generator makes sense. My Iota charges at 20% of my bank capacity.

wellbuilt · May 2014

Re: off grid cabin/ home

wow ,
plow man , you are living the dream .
sounds like a good time.
In communist ny we have all kinds of rules and regulations to live by .
I will end up with a Honda 3500watt generator soon .
my well guy is drilling the water well next week , I will start soon .
thanks for the reply .

Thom · May 2014

Re: off grid cabin/ home

I would not use a propane refrigerator cheaper to go 120v.

Thom

wellbuilt · May 2014

Re: off grid cabin/ home

Thanks for the reply thom ,
What cost more Running the frig on propane or buying the unit it self ?
Im still trying to get a handle on the watt hour usage and how I will use the system it self .
I mite just build a small system for lite at night and radio .
I will need to keep reading and asking questions .
thanks much

mike95490 · May 2014

Re: off grid cabin/ home

I think another thread hashed out that if you use a fridge more than 9 months a year, 120VAC with efficient gear & PV was less in the long run than filling LP tanks.

Plowman · May 2014

Re: off grid cabin/ home

wellbuilt wrote: »

wow ,
plow man , you are living the dream .
sounds like a good time.
In communist ny we have all kinds of rules and regulations to live by .

I don't know about living the dream, but it's definitely been fun experimenting with off-grid living, something I've been thinking about for almost ten years and now I'm finally doing it. Next step is to build a "tiny cabin" on wheels, one with a woodstove so I can put my propane heaters away for good. I live/work on a tree farm and have no way of burning wood for heat indoors. Silly.

Re. refrigeration, I use an RV propane fridge, works quite well despite being 18 years old. I only started using it on propane a month or so ago, still figuring out exactly how much propane it burns, but the last tank I measured I was using almost exactly 0.25 gals/day to run the fridge and the stove. Not sure how much propane each appliance is using since they're on the same tank.

The 12V draw of the fridge is minimal, it draws 0.3 amps, but not continuously. Roughly 4.5 amp-hours per day. I measured how much it draws when plugged into grid power last year, it's crazy inefficient when run on AC (147.3kWh/month).

If I didn't have the propane fridge I'd try converting a small chest freezer to a fridge using a Johnson controller. I believe these may draw even less power than my RV fridge, and no propane required---I've seen figures between 200 Wh/day and 450 Wh/day.

For lighting I mostly use a regular AC lamp with a 7W LED bulb in it. Draws 0.58 amps @ 12V (accounting for inverter draw). I tested an RV-type fixture with an 1141 LED, it only draws 0.13 amps, and no inverter required. Unfortunately my panel/battery system is 100 feet away, so I can't use 12V lights/appliances anymore. Also use some AA/AAA lanterns and puck lights, but only one I like is the Energizer puck light.

My computers draw the most power, my little netbook with my smart phone tethered to it draws 2.68 amps @ 12V.

vtmaps · May 2014

Re: off grid cabin/ home

wellbuilt wrote: »

I wont know about the well pump till I have a well drilled , maybe next week, some wells are drilled 900 feet deep and have water 5' down some are 4/500 feet and the pumps are down 200' ?
I would say the pump would be 1 hp 240v ?
<snip>
I would be hunting for a new generator at lowes.

First, I agree with the others... don't burn propane for refrigeration.

Regarding the well pump... For many off-gridders the well pump is the defining load about which the system is designed. If you are faced with "super-sizing" your entire system just to pump water, then you should look into a more expensive, but much more solar-friendly water pump. Lots of threads on this forum about that.

There is no Lowes near where I live, but if it is anything like HomeDepot, I would not buy a generator there... Lots of cheap generators and you get what you pay for (or even a little less).

I like your plan to put the batteries & inverter in the garage... is the garage detached or connected to the house? What are the temperatures likely to be in the garage?

Where will your array be mounted (roof, pole, ground mount)? Where are you located (snow? desert?).

--vtMaps

Plowman · May 2014

Re: off grid cabin/ home

Plowman wrote: »

If I didn't have the propane fridge I'd try converting a small chest freezer to a fridge using a Johnson controller. I believe these may draw even less power than my RV fridge, and no propane required---I've seen figures between 200 Wh/day and 450 Wh/day.

Whoops, I just realized I miscalculated, confusing 12V with 120V (not the first time). A 300Wh/day fridge @ 120V would draw 25 ah/day @ 12V. Compared to the 4.5 ah @ 12V my propane fridge's controller draws.

Long-term cost-benefit might still tilt towards the converted chest freezer since propane ain't getting any cheaper.

vtmaps · May 2014

Re: off grid cabin/ home

Plowman wrote: »

Long-term cost-benefit might still tilt towards the converted chest freezer since propane ain't getting any cheaper.

Actually, the price of propane has dropped considerably in the past 5 months.

One of the best reasons to avoid propane fridge is the exhaust. In RVs with propane fridges, the exhaust is vented. Vermont's residential energy code prohibits the use of unvented propane refrigerators in a home.

If the power requirements of an electric fridge cause you to run your generator a few more hours per year, that's not so bad... I would rather burn a bit of fossil fuel outdoors in my generator than indoors in my fridge.

--vtMaps

Plowman · May 2014

Re: off grid cabin/ home

vtmaps wrote: »

Actually, the price of propane has dropped considerably in the past 5 months.

That's just seasonal differences in cost, it'll go back up next winter. There's been a large increase in exports of propane in recent years, which is great for propane producers, not so much for domestic propane consumers. This played into the shortages some regions experienced over the winter.

One of the best reasons to avoid propane fridge is the exhaust. In RVs with propane fridges, the exhaust is vented. Vermont's residential energy code prohibits the use of unvented propane refrigerators in a home.

Mine is in an RV and is vented outside. I haven't noticed any venting issues, no smell and the CO meter I have mounted a couple feet from it hasn't registered anything. I certainly wouldn't keep one of these indoors without some sort of vent to the outside.

If the power requirements of an electric fridge cause you to run your generator a few more hours per year, that's not so bad... I would rather burn a bit of fossil fuel outdoors in my generator than indoors in my fridge.

25 ah/day for a converted freezer is nothing to sneeze at, I wouldn't want to rely on a generator to recharge batteries for this application. That'd get expensive real fast.

Assuming half the 0.25 gals/day of propane I'm using for my fridge and stove are for the former (total guestimate), I'd need 45.6 gals of propane a year to run the fridge. At current local retail prices that's $136/yr, or $11.37/mo. Not great, but not terrible. Two 100lb tanks would power my fridge for a year.

AuricTech · May 2014

Re: off grid cabin/ home

One thing for non-RV off-grid folks to remember is that, for an RV-based system, rooftop space is a scarce resource. As such, running a fridge on propane may well be a better solution than relying on a generator to provide overdraft protection for the battery bank.

One thing for RV off-grid folks to remember is that, for a cabin/home system, rooftop space is unlikely to be the limiting resource. As such, designing a PV system with the intent to use electricity to run the fridge may well be a better solution than dealing with the issues of running a fridge on propane, even if it means running a generator on rare occasions.

Have I adequately split the baby? :roll:

Plowman · May 2014

Re: off grid cabin/ home

AuricTech wrote: »

One thing for non-RV off-grid folks to remember is that, for an RV-based system, rooftop space is a scarce resource. As such, running a fridge on propane may well be a better solution than relying on a generator to provide overdraft protection for the battery bank.

True enough, I only have room for 4 panels on a little cargo trailer. None on the RV itself since it's situated in full shade to avoid having to run AC in summer.

There's also the fact that most RVs come with propane fridges, so no reason for cheapskates like myself to buy an electric fridge

I'm not a big fan of propane, and would prefer a solar-electric fridge, but gotta go with what I got. If I was starting from scratch I doubt very much I'd buy a propane fridge, for several reasons, not the least of which is that they're rather spendy, even if purchased used.

wellbuilt · May 2014

Re: off grid cabin/ home

Plow man ,
I love burning wood , Ive really never had a house with real heat .
We have burnt wood for 20 years .
I have not even tried to lite the nat/ gas boiler since 06
Thing have gotten real good the last few years, my sons cut/ split the wood and the girls stack it and drag the logs in the house . I have 10 kids , of fire wood age .
Wiffey keeps it burning all day .
We heat 4500 sq feet most of the year, with one large stove in the center .

My main reason for the propane frige was to get the beer cold fast .
I could just buy the frig and drop a tank next to it and the beer is cold .
We mite even buy the frig get it running and build the shed around it.
I do have space for a chest size frig in the kitchen that sounds good .
VT
If the water in the well is close to the top I mite start off with a home made gulper air lift pump .
That fills a large tank (500 gallons ) in the corner of the garage .
I can pump the air with a small air pump and raise the water in to the tank .

Its cold here and I get a lot of snow, Im on a peak at 3000' in ny Very windy with lots of sideways rain and snow .
Im trying to get a friend to sell me his D4 track loader to push snow, every one uses a wheel loader now .

There is not many places to buy generator here if I need a genny in a pinch ,on the weekend HD or lowes is the only place.
I would like to order a genny from Central Main diesel , but what to get?
I get free diesel heating oil all the time so a diesel would be nice .

I was thinking of drilling a well casing in to the stone to mount 8/ 10 solar panels and making it so I can spin it to the sun east to west .
My main roof will be built dead south and framed at 42o to mount the panels to the roof 39' long .
The pole mount mite be good for now .
The roof would be easy to mount harder to clean snow .

The garage is attached, The battery bank can be mounted in the garage, it will be cold with no heat.
The house is on rock with a concrete slab and radiant heat I will loop some tube under the battery bank and on the floor where I mite need to sit and work .
I like a dv hi out put propane boiler as back up and wood boiler in the utility room next to the garage .
If we are not there in the winter there will be no heat.

A friend gave me a old 26' air stream trailer to day it been closed up for 6 years and the door was left open some time ago
, its kinda rough in side, but workable . It looks good for 40+ years old .
It has 4 bunks and good storage .
Do you think I should go 24 or 48volt system ?
Who makes a inverter with generator assist ? thanks john

mike95490 · May 2014

Re: off grid cabin/ home

wellbuilt wrote: »

..

A friend gave me a old 26' air stream trailer to day it been closed up for 6 years and the door was left open some time ago
, its kinda rough in side, but workable . It looks good for 40+ years old .
It has 4 bunks and good storage .
Do you think I should go 24 or 48volt system ?
Who makes a inverter with generator assist ? thanks john

I've heard Airstreams are hard to properly insulate.

48v systems have less copper loss than 24v, but the inverters are generally larger, and may have more self-consumption than small loads.

What's your weather like - will you need lots of generator run time, or just a bit weekly in the winter ? 900 & 1800 RPM gensets have longer life, but are usually giant machines. What's your cold weather starting requirements - will a diesel need a electric preheater ? special cold weather oil? Is it too cold for propane genset?

wellbuilt · May 2014

Re: off grid cabin/ home

I think the trailer should only be needed for 2 winters at most, Then we could move inside maybe pitch a tent on the second floor to have a clean warm place to sleep or insulate and sheet rock the garage and use a small stove there .
Building permits are good for 18 months here after that they want to fine you .
Im on a three year plan soooooooo we will see what happens , I mite have to sweet talk the inspector .

Mike its 2014 now, diesels are really pretty good about starting .
All my trucks start good down to 0 and the excavators, track hoes, skidsteer will start as long as the fuel runs .
If its real cold I use a propane torch in the intake and just warm the air , or a small jet heater .

I don't think a propane injected Honda will last long the valves don't get any lube .
They burn lots of fuel .
I would need a large propane tank and I don't think I could burry it because of the rock .
I was thinking 5 100lb tanks would last me from thanksgiving to Easter for a frig, water heater, stove, laundry
If I need more fuel i could run to town for a bottle .
The propane truck is never getting to me , If the gas company delivers the gas its almost twice the price .
At my old price 400 lbs @$ 140 vs 400lb at $279 delivered . Plus they want to you to pay rental on the tank.

As far as my power usage I have no clue . If im watching a 42" Samsung led tv with direct tv box , charging a cell phone , using 2 led lite Cooling some beers in a chest frig With wiffey running the water pump and running a lap top who knows how many watt that is , (1500 watts at one time maybe ?) I don't have the equipment to test . ? If i double the size of the inverter and go with a 3000 watt unit . Would that be good ?
It seem like a 1000 watt magnum inverter uses the same power on stand by as a 4000 watt magnum inverter.
I like the 4000 watt magnum inverter with generator support .
are there inverters like this with less wattage ?
John

mike95490 · May 2014

Re: off grid cabin/ home

2014 diesel generators are still compression ignition engines. My replica 1930 diesel hand cranks easier and down to 0F, the new electric start Robin/Subaru/Hatz needs preheat assistance at 34F What a pain! I lost ground, but at least it's CARB certified. Larger engines sometimes have glow plugs, some have intake grid heaters, or the propane torch. Just something to be aware of. Maybe Chris will chime in with his cold weather engine experience.

Only YOU can develop the power plan. What size is the water pump ? 240V or 120V? Inverter has to be large enough to start the pump when some of your baseline loads are on. (Fridge or washer)

Do you want 2, 3 or 4 days of autonomy before you need to start the genset ? Larger battery banks need larger arrays to keep them going. 2 days autonomy and some generator runtime is lots less investment than 4 days autonomy

vtmaps · May 2014

Re: off grid cabin/ home

mike95490 wrote: »

Do you want 2, 3 or 4 days of autonomy before you need to start the genset ? Larger battery banks need larger arrays to keep them going. 2 days autonomy and some generator runtime is lots less investment than 4 days autonomy

My advice: go for 2 day autonomy. If you have 4 days autonomy it means that when you have multiple sunny days your overnight discharge will be very shallow. That is not good for most types of batteries. Some controllers have the ability to NOT charge the batteries on days when the SOC starts out too high. Of course, if it skips charging today.... it will probably rain tomorrow.

One thing (other than buying more days of battery autonomy) that can help reduce generator run time is a few extra solar panels. That gives you the ability to charge the batteries on more of those marginal days.

--vtMaps

Cariboocoot · May 2014

Re: off grid cabin/ home

vtmaps wrote: »

My advice: go for 2 day autonomy. If you have 4 days autonomy it means that when you have multiple sunny days your overnight discharge will be very shallow. That is not good for most types of batteries. Some controllers have the ability to NOT charge the batteries on days when the SOC starts out too high. Of course, if it skips charging today.... it will probably rain tomorrow.

One thing (other than buying more days of battery autonomy) that can help reduce generator run time is a few extra solar panels. That gives you the ability to charge the batteries on more of those marginal days.

--vtMaps

I concur. More than 2 days capacity leads to a system that is oversized for the majority of the time, and as such is waste of money.

If you know you have several 'slightly cloudy' days you can push the array size up to increase the peak charge rate (staying within the batteries' limits) to compensate at least partially.

Right now I am experiencing rainfall so heavy the satellite connection is slow. The panels will produce such a small fraction of their normal output as to be useless. Making the array 10 times the size would barely increase the current output under these conditions but would cost a lot of money. Instead I will start the generator and run it for a couple of hours. I will also turn on the water pumps and make full use of the gen run time. Most of the time the generator is not used. Much cheaper than a whole lot of panels that can't guarantee output in bad weather.

South Africa · May 2014

Re: off grid cabin/ home

Same here, I fall back onto the grid for rainy cloudy days. Cheaper than a huge battery bank and array to charge it.

BB. · May 2014

Re: off grid cabin/ home

And if you mess up and kill the battery bank by accident, it will only cost you half as much to replace the bank.

Accidents do happen (also known as teenagers).

-Bill

wellbuilt · May 2014

Re: off grid cabin/ home

Well ,OK
I think 2 days worth of power seems workable
You guys , VT , caribo, have a similar size battery bank @ 24volts
Mike running 800 ah at 48volts seems very large .
What is the cut off point between 24v vs 48v system .

Say I stick with eight L 16 battery@ 380 ah on a 48 volt system that would give me 380ahs @ 48v
I could get the same type battery in ( 4)12volt 200ah @ 48volt
I would have twice the capacity with the L16 but could go with a 48 volt system .
On the other hand I could go with a 24 volt system and run 2 string of (4) L 16 @ 24volts

If I use 4 L 16 @ 380 ah / 95 ahs x 24volts=2280watt hrs for 25% sod one days power .
If I double the size of the bank 8 l16s that would bring me up to 4500 watt hrs +
It seems to me I would need somewhere around 3000/ 3800 watts just looking at generic #
I have a watt meter coming from amazon and I can check the power usage on some things around the house to get a power usage idea .
Most of the inverter / chargers burn about the same watt hrs in stand by mode .
john

Cariboocoot · May 2014

Re: off grid cabin/ home

wellbuilt wrote: »

Well ,OK
I think 2 days worth of power seems workable
You guys , VT , caribo, have a similar size battery bank @ 24volts
Mike running 800 ah at 48volts seems very large .
What is the cut off point between 24v vs 48v system .

Say I stick with eight L 16 battery@ 380 ah on a 48 volt system that would give me 380ahs @ 48v
I could get the same type battery in ( 4)12volt 200ah @ 48volt
I would have twice the capacity with the L16 but could go with a 48 volt system .
On the other hand I could go with a 24 volt system and run 2 string of (4) L 16 @ 24volts

If I use 4 L 16 @ 380 ah / 95 ahs x 24volts=2280watt hrs for 25% sod one days power .
If I double the size of the bank 8 l16s that would bring me up to 4500 watt hrs +
It seems to me I would need somewhere around 3000/ 3800 watts just looking at generic #
I have a watt meter coming from amazon and I can check the power usage on some things around the house to get a power usage idea .
Most of the inverter / chargers burn about the same watt hrs in stand by mode .
john

I can think of no better example of why it's important to work out how many Watt hours you need before planning a system.

System Voltage basics: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power

The short differences are: number of parallel battery strings required to get the power you want, as in try not to go beyond two if at all possible; try to keep it to one charge controller, which essentially puts an 800 Amp hour cap on any system Voltage. Surprisingly these simple rules-of-thumb work out well in most cases. Of course there are always exceptions.

off grid cabin/ home

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