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Small Cabin Forum / Off-Grid Living / Solar for 12x20 cabin
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Murph
Member
# Posted: 23 Sep 2020 12:04
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Hey guys, new here and new to solar power. I have a recreational cabin in the woods off the grid. Currently we use a lot of batteries and small solar lights for the nights. Looking at putting in a solar kit. Want to run 6 led style lights, charge some electronics, run a kureg coffee machine, basic fan for hot nights. Have a wood stove for heat and gravity water tower for water.

Was thinking of 400 watt solar panel kit, 4 golf cart batteries, 1500 watt invertor and a charging regulator. We spend mostly weekends here and the odd week here and there. Would this be enough? Overkill? I have a generator for backup
Thanks

jhp
Member
# Posted: 23 Sep 2020 13:07
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Is the Keurig a deal breaker for you? By far that is going to be the biggest energy hog based on what you listed. Depending on the model you have, that inverter might not even be big enough when the brew cycle kicks in.

If you have to have it, I'd probably look for the "dumbest" K-cup compatible brewer you can find that isn't drawing electricity all the time.

Even at "idle" 60 watts x 24 hours a day is 12ah.
Depending on the size of the batteries you're looking at, that might be 10% of your capacity just to have a coffee maker on standby.

To size the rest of it, I'd list out all the electronics you plan on using, figure out their individual consumption per hour and per day, then run it through a sizing calculator that will help you figure the size of the battery bank and panels to give you whatever amount of storage (in days worth of electricity) you are looking for.

From Keurig's site:

Keurig® home brewers use the most power during their initial startup. When heating for the first time after being off, peak usage is 1,500 watts. If the power is kept on, the brewer will keep the internal tank up to temperature using between 200 – 400 watts when heating. While idle and not maintaining heat, the brewer will use the average electricity of a 60 watt light bulb.

Nobadays
Member
# Posted: 23 Sep 2020 13:39
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+1 on jhp.... That Keurig at 1500 watts will likely stress, if not shut down a 1500 watt inverter unless it is a higher dollar unit with the ability to supply a start up load for an extended period. A "dumb" K-cup machine, as jhp suggests would be best if you aren't using a pure sine wave inverter. Some, not all, electronics just don't like modified sine wave power.... most motors don't like it at all.

Pour overs make the best coffee with fresh ground beans! A little pulse style coffee grinder (they will work on modified sine wave), a Melitta style pour over, filters and a kettle on the stove will make good coffee and your solar planning easier and cheaper.

NorthRick
Member
# Posted: 23 Sep 2020 13:42
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I'd run the coffee maker off the generator. Fire it up, make your coffee, turn it back off. Your proposed solar setup should run the rest of the stuff.

Murph
Member
# Posted: 23 Sep 2020 14:23
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Ok. Appreciate the advice. If the coffee maker is running on genny, or I decide on a percolator, would it be best to keep things at 12 volts then? I can get lights, fans, switches and phone chargers pretty easily. Or is it better just to plug into the invertor. I am just trying to keep it simple, and even use the generator to charge up the batteries on those crappy days

jhp
Member
# Posted: 23 Sep 2020 14:36 - Edited by: jhp
Reply 


I ran a small solar setup before I had grid power, and I tried to keep as much 12v as I could. LED lights, chargers, and even a boombox radio (or car stereo) you can run right off the 12v and not waste by having to run the inverter and convert it to AC. If you check the draw on your inverter, that too just running is eating up more watts than you think.

I only ran a TV (again a modern LED), media box, and things like drill chargers off the AC.

For some perspective, at night on my system running a couple lights, a TV and media box i was drawing between 40 and 50 watts total. That's less than the Keurig on idle.

If you plan ahead carefully you can size the system right and save money in the long run.

Murph
Member
# Posted: 23 Sep 2020 14:46
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Did you wire up to a fuse box or panel?

jhp
Member
# Posted: 23 Sep 2020 15:24 - Edited by: jhp
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I did, it was pretty easy.

I got a 5 gang switch panel on Amazon (the kind you'd find in a boat) and then wired that up to an automotive style fuse block. That fuse block had 12 slots (I think) I used for each circuit and a common bus for the negative.

I then wired a couple of meters between my battery and load center, and between my panels and battery so I could check the state of incoming and outgoing power usage without guessing.

I think it was maybe $50 for both the switch panel and fuse block. Each of the power meters was $15.

My loads were very simple so I felt pretty good running boat/automotive style setup. If you wanted to bring the generator into the picture and step up the power running through you might want to consider a real fuse panel.

Murph
Member
# Posted: 23 Sep 2020 15:35
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That sounds perfect. I would probably just charge the batteries direct from the generator to the batteries using a good quality battery charger. I would use a battery disconnect switch mounted just after the batteries so I can shut the power off to cabin

Murph
Member
# Posted: 23 Sep 2020 15:37
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Maybe I should look for 12 volt batteries instead of 6 volt.

jhp
Member
# Posted: 23 Sep 2020 15:43 - Edited by: jhp
Reply 


That's exactly what I did. I actually only had one 100ah battery, if it had gone a couple days without sun I'd just use a battery charger on a low setting and run things right from the generator for the day.

Most days though with my overall low power draw by lunch my batteries were topped off and I could run whatever power I wanted without the batteries coming off of float voltage. Then after the sun went down I'd have about 12-14 hours of runtime (if I wanted) before hitting 50% discharge. Most nights I never even came close to using that.

There are lots of reasons to go 6 vs 12 vs whatever for your system. I wanted to keep it simple as possible and at the time a decent 100ah AGM battery was about $150 (ish) on Amazon.

Murph
Member
# Posted: 23 Sep 2020 17:35
Reply 


Thanks, appreciate the advice. Take out coffee maker and I think we are set. I’ll double check my needs and go from there

Brettny
Member
# Posted: 23 Sep 2020 19:24
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Really alot depends on your solar exposure. I have the system you want to build and run a 4.3cuft mini fridge and have no special 12v anything. We have 100ft of string lights outside and about 50w of lights Inside. But really the fridge is a big energy hog.


Our system is 470w of solar, 40a EP ever CC, 4 6v golf cart batteries, 30a RV charger, 1kw sportsman inverter generator and a 1200w xantrex inverter. All that along with a 4.3 cut mini fridge I have less than $1200 into it. Generally I run the generator about 2-4hrs a day because I'm still getting use to the system but also haven't seen it below 70%. I'm also only getting 3hrs of direct sun on my pannels. This last trip I even used a small shop vac for about 15min with no generator running. I did only run the generator for 2hrs this trip.

The good thing about a weekend place is if your sun exposure or solar isnt enough...just add more batteries. By the time you come back they will be fully charged. I found that the 6v flooded batteries even brought down to 50% should last us nearly a decade in cycles.

Murph
Member
# Posted: 23 Sep 2020 21:55
Reply 


Thanks Brettny. All things to consider. A little fridge would be nice...lol. Always looking for good ideas and advice. It is possible I may want to expand in the future

AKfisher
Member
# Posted: 25 Sep 2020 12:58
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Quoting: Murph
Was thinking of 400 watt solar panel kit, 4 golf cart batteries, 1500 watt invertor and a charging regulator. We spend mostly weekends here and the odd week here and there. Would this be enough? Overkill? I have a generator for backup
Thanks


Do you have everything picked out that you will buy? I am in the same boat as you, just need solar and batteries for lights, but need an inverter so I can charge. It has been tough getting my brain wrapped around the electical department of the building.

Brettny
Member
# Posted: 25 Sep 2020 13:09
Reply 


Inverter/chargers are very expensive. Look at an inverter and use a RV onboard charger. My Iota 30a charger was nearly new and $100 shipped. My xantrex 1200w pure sine wave inverter was new but missing a few covers, $140 shipped. Both off ebay. You can do alot of work with 1200w esp when it's a good inverter and the starting watts is 2x the rated and it will take 2400w for 20sec.

Steve961
Member
# Posted: 25 Sep 2020 14:09 - Edited by: Steve961
Reply 


My first suggestion would be to eliminate the Kureg and find another way to make your coffee - maybe on a propane stove. This alone will allow you to have a more reasonably priced solar system. I would also recommend using, and wiring the cabin for, 120 VAC for most lighting, chargers, small appliances. Whatever money you save by not having an inverter will be spent on the extra cost for 12 VDC bulbs and appliances. It's also nice for when my friends come to the cabin they can use most of their chargers and other accessories.

A great small inverter is the Morningstar SureSine (300 watts continuous, 600 watts surge), and is only $266 on Amazon. Very clean power that will not fry even the most sensitive electronics. I run lights, a TV, small vacuum cleaner, tool and battery chargers, and even a small rice cooker off of mine. I do use 12 VDC for my Coleman Sterling cooler and water pump though.

I also agree with Brettny to get a separate inverter and charger. The SureSine and Iota charger will be cheaper and more reliable than most integrated units. My power center below has a 128 watt roof array, 190 watt removable ground array (which I almost never use), 110 AH AGM battery, SureSine inverter, Iota 30A charger, and an Iota automatic transfer switch for a generator - which I haven't used for 7 years or so. I do plan on upgrading to a 220+ AH battery this fall to give me a bit more flexibility during the colder months.

.
PowerCenter_Small.pn.png
PowerCenter_Small.pn.png


toofewweekends
Member
# Posted: 25 Sep 2020 20:39
Reply 


We have a very similar set up for our place north of Anchorage. From mid-February to October, there is plenty of 120v power for lights, watching dvd's, a microwave, charging phones, etc. I've run an ice maker for an hour or more when the panels are getting good sun, a vacuum occasionally, etc. for coffee, we boil water on a propane stove. We use a modified sine wave inverter that we've had for a long time; haven't fried anything yet. In mid-winter, we'll run off batteries, then top them off with a generator and Iota charger. If I need to run tools, and have a bunch of stuff going at once, I just shift to the generator.

Heymirth
Member
# Posted: 26 Sep 2020 08:17
Reply 


Great Thread.
I am just starting to plan a “weekend shed/one room” camp. I enjoy learning from here and YouTube

Thanks for all the knowledge

mj1angier
Member
# Posted: 26 Sep 2020 11:01 - Edited by: mj1angier
Reply 


I guess I am different than some folks, I try to oversize my system to meet futer need vs. having to rebuy to upgrade. I went with inverter/ charger and lith. battery. I hard wired it all in in our 12x20 "shed" cabin. I have solar and run the genny in evenings if we need extra power for tv- but it will last for 2 days just off battery. Photo of my system as I was putting it in.
power.jpg
power.jpg


Murph
Member
# Posted: 27 Sep 2020 08:29
Reply 


Quoting: AKfisher

Do you have everything picked out that you will buy? I am in the same boat as you, just need solar and batteries for lights, but need an inverter so I can charge. It has been tough getting my brain wrapped around the electical department of the building.


I don’t have anything picked out yet. Reading,learning and trying to wrap my head around it all. Lol. Some of the info here has given me a bit more to think about. I can get batteries from work at a good price. We don’t live there, and is a recreation property, so we just want some basics. We did decide on a percolator coffee maker so that makes things a bit easier.

Steve_S
Member
# Posted: 27 Sep 2020 14:56
Reply 


@Murph.

I'm 100% offgrid solar powered. Using 24V 910AH Lifepo4 & 856AH of Heavy Lead Rolls Surretes. (being phased out).

I NEED my coffee and am serious about my morning Joe.. Kids, Critters, stay away from me till Mugga One is IN HAND ! Coffee makers are all Energy Pigs BUT I puchased an OSTER unit that has a Thermal Carafe, it only run 6 minutes to brew 10 cups and them nothing as there is no warmer. It also only uses about 900W so it's not a hard hit on the system.

LINK: https://www.oster.ca/en_CA/coffee-and-kettles/coffee/oster-10-cup-optimal-brew-therma l-programmable-coffeemaker-stainless-steel/BVSTPSTX95-033.html#start=4

Please head THIS ADVICE:
Do NOT buy anything till you have a plan, know what is needed and what the result will be in the end. With a proper plan, you can even build your system in stages as you decide to expand IF that's part of the equation.

There IS planning required because it's not just "plug & play" as it were. (that does exist but at huge $$$$) KISS is often the best solution, especially for smaller projects.

It does take a certain amount of panel to charge batteries and that depends on the amount of battery there is to charge. Depending on Chemistry chosen, this can change too. For example, Lead Acid versus LiFEpo4, li-Ion, LTO and so on. The SCC (Solar Charge Controller) has to be suitable for the amount of panel & size of battery bank as well.

Over the past 5 years a LOT has changed and grown up within the Renewable Energy Sector. Many people looking for a Good Solid Stable and not overly complicated setup, go for the AIO's (All In One) units such as MPP-Solar or Growatt. These have the Solar Controller, Inverter & Charger all built in (they are modular components and repairable / replaceable) which really simplify a lot of installation issues.

LINKS:
https://usamppsolar.com/
https://www.growatt-america.com/

NOTES:
- Some equipment is UL/ETL/CSA certified which does put the price up a bit.
- They offer LF & HF models. LF = Low Frequency, HF = High Frequency. HF is the way to go !
- They all support Lead Acid to Lithium Variants.

REF LINK:
https://www.magnum-dimensions.com/knowledge/high-vs-low-frequency-inverters/inversion -methods-explained-high-frequency-vs-low

There are many options, considerations and options available to consider. We also have many experiences & connections with Manufacturers, Wholesalers & Resellers. If you check out https://diysolarforum.com/index.php you'll find me there as Steve_S as well. That site is oriented specificall at the DIY Solar Crowd, there are manuals, guides, instructions and much more all there for you to access. Many of us, help folks plan out systems in detail as well.

Hope it helps, Good Luck
Steve

Murph
Member
# Posted: 27 Sep 2020 17:41 - Edited by: Murph
Reply 


Thanks Steve. I still think I’m the end I will want to keep it simple. Just having a basic power source to supply lights would be a huge improvement. But this thread definitely has me thinking of what I want vs what I need. Lol
Any link to a page where I can calculate the amount of power needed? Thanks

Steve961
Member
# Posted: 28 Sep 2020 00:03 - Edited by: Steve961
Reply 


If you do end up going with an inverter and 120 VAC, you should get a "Kill A Watt" meter. This will tell you exactly how many watts of power a device actually uses. Add up the watts for each device and how many hours each will run to get your total watt hours for the day. You can also estimate how many devices might run at the same time to calculate peak running watts for sizing your inverter. I know that I can't run every device that I have at the same time without overpowering my inverter (Morningstar SureSine), but it has never been a problem for me.

Kill A Watt Meter

Brettny
Member
# Posted: 28 Sep 2020 07:12
Reply 


My killAwatt meter is so inaccurate I have to calculate how much it's off in amps to figure out how much time its actualy ran...for a fridge.


A killAwatt only shows you 120v used. Theres losses involved with making 120v and what you really care about is battery condition.
https://www.amazon.com/gp/product/B07FGFFHC6/ref=ox_sc_saved_title_9?smid=A3JXNUUKLAS GK0&psc=1.

A Keurig should run fine on a battery bank the size you want to build. Yes they are power hogs and prob run near 15a if memory serves me right. But then only run for 2min. This is also why I have a rv charger. Something really pulls the system down, just use the charger.

We got our first real cloudy day useing our system running outdoor string lights, the fridge and we now have lights in the kitchen. I also used the 7amp shop vac for about 10min. I ran the rv charger for about 4hrs in 2 days. The 1kw sportsman inverter charger run a 30a RV charger real well and you almost cant hear them at the end of a 100ft cord.


Someone said just to run everything in 120v and there right. By the time to run wire and buy special bulbs your not saving a whole lot and your now tied to a system voltage. I built my system with as many 12/24v components as I could so i can change if i wanted.

Also dont put your inverter in the area you sleep. They make noise and no one wants that in the silence of the woods.

jhp
Member
# Posted: 28 Sep 2020 08:34
Reply 


Quoting: Murph
Any link to a page where I can calculate the amount of power needed?


Here's a couple you can try

https://www.wholesalesolar.com/solar-information/offgrid-calculator

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https://www.altestore.com/store/calculators/load_calculator/

https://www.altestore.com/store/calculators/off_grid_calculator/?dwhrs=0

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