diy solar

diy solar

Looking for input/advice for off-grid Cabin.

IrishViking505

IrishViking505

New Member
Joined
Jan 10, 2021
Messages
5
Location
New Mexico Territory
Hello all!

I am new to this site and new to the world of solar power.
I have done some research, but figured I could obtain a clearer picture by asking my questions here.

My wife and I are about to move into our off-grid cabin. Our plan is to live there for approximately 2 years.
The cabin currently has a single panel 12V system that consists of a simple screw-post hub, battery meter and 4 deep cycle batteries that have been fully discharged who knows how many times. This system has most likely been part of the cabin since it was built back in 2006.
We purchased the cabin last year.
Currently, it powers 3 lights, and some old cigarette lighter style wall plugs that we use to charge phones and tablets.


I am needing to install a new system that will be powerful enough to run everything we need...and this is where my questions come in.

This is a list of everything that we will need to run on the new system:

-Two (2) laptop computers - up to 10 hours per day continuous (+charging) for work.
-Internet modem - on all day.
-Dish Hopper Satellite Receiver with DVR - on all day.
-Two (2) 24" Flat screen TVs (only one on at a time) - on for up to 8 hours per day.
-Three (3) small 12V water pumps for outdoor shower, kitchen sink, and a back-up (all coming from 500 gallon rainwater tank). These will be used as needed, intermittently throughout the day.
-Capability to charge three (3) cell phones each day.
-Capability to charge two (2) Amazon Fire Tablets each day.

*My plan would be to install three (3) 120V AC electrical outlets, and also keep the current 12V lighting system that is in place.
We get over 300 days of full sunlight each year.

I need to power all the above with wiggle-room for additional power if needed.

I am not savvy on solar, but I am intelligent, educated, and capable. This will be all DIY install.
Wondering what would be a good option for a complete system to handle the above?
I know there are Cadillac systems, and Yugo systems. I am looking for something low to mid range that will last a few years but not break the bank.

Appreciate your inputs and assistance on the size of the system and components I would need to succeed here.

Thank you so much!

Liam
 
What are your plans for refrigerator, freezer?, water heating system?
We have a Bosch on demand water heater (LPG) that I installed from HDep about 12 years ago. It luckily does not need electricity. It has a standing (small) pilot light (pizo igniter - like a BBQ) and as soon as we turn on the faucet it sense volume and fires. Been pretty darn good.
We are not off-grid but try to conserve. Wood stove heat take care of 960 square feet.
Lastly I was skilled in LPG and somewhat proficient with electrical but there are many nuances to Solar....Been following this forum for quite awhile, lots of very sharp folks contribute. I would just say read reviews of equipment that others have purchased to avoid being misled as to what a particular item will do.

We are getting 68%-75% productivity from our modules that are Jinko 72 cell premium 320w. You'll never get full charge but still have to do the math to be safe....That's one thing I never knew when beginning this last summer (I am a noob)
 
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Regarding tankless water heaters. I've had both the manual (3 knob) LPG on-demand water heater that uses a battery for ignition and the electronic (digital control) units that allow you to set an exact temp and leave it but they need 300W or so in operation (fans + electronics)... several of each. The manual one is ok if your water temp stays the same all year long, but if it varies so will your temperature where the electronic one maintains its set temp and has anti-freezing protection too. I'll pony up the 300W in a heartbeat! The manual one is nice in that where you didn't have hot water now you do without external power, but the electronic one is more of what you expect when you turn the shower on. I've had way too many too hot, and too cold showers.

Edit: Only 300W when using hot water, 18W (or so) in standby.
 
I had this discussion with the neighbor across the road some months ago, and I can outline what we talked about for your benefit. What you want is something that works now, but is incrementally expandable for your future needs. Here's what we discussed....

Start with a system voltage higher than 12V. The serious off-grid solar starts at 24V and reaches 48V. I have both. A good rule of thumb is if load never exceeds 1000W, then 12V is OK. If loads reach 2000W, then go with 24V. If loads exceed 2000W go with 48V. It looks like what you have now most likely won't reach 2000W, but might in the future.

You can start out with a smallish 24V system that won't cost too much. I'll throw in some math so you can update the numbers with your real-world findings.

You could start with a 24V battery bank made of four 6V golf-cart batteries. Assuming you don't want to deplete more than 25% per day, and gives you a day of autonomy before dropping to 50%, then you get.... 225AH X 24V X .25X = 1350Wh or 1.35 kWh.

Assuming you have 225Ah batteries you want to charge them at about 1/10 or 1/8C. So, 225Ah X 0.1C X 26V charging X 1.25 loss factor = 731W of panels. I can get 260W grid-tie panels for about 60$ each, so that would be 180$ for 780W.

You'll need a 24V charge controller that can handle that much power, which would be documented in amps. It works out to be....
(780W/26V) charging X 0.8 loss factor =24A. An Epever 40A would be fine. They cost ~135$ right now.

Lastly, you need an inverter. I'd say go with at least 1500W, because I've heard of people complaining that their 1000W unit couldn't start their frig. Look at this Samlex.... https://ressupply.com/inverters/samlex-pst-1500-24-pure-sine-wave-inverter
It has NEMA plugs, but it can be hard-wired into an electrical panel.

If you want to keep the 12V lighting, you can get 24V to 12V converters cheaply.
www.ebay.com

24V to 12V 20A DC DC Converter 20AMP 240 Watt Voltage Step Down Module | eBay

This converter can not be connected to solar panels or wind turbine directly. DC-DC Converter. Over temperature shutdown, Short circuit protection, Output reverse polarity protection. GOLF ADAPTER. 100% full stable output Current.
www.ebay.com

Keep in mind that this is MY idea of a starter system. If you want to power a frig, it might work, but you'll want to invest in bigger batteries and more panels before you get one. Eventually you will want bigger batteries, more panels, and a bigger inverter. These though can be added in 1 by one. Add propane heat for hot water, and either propane or wood to heat the home, and you will be quite independent.
 
Last edited:
road glide said:
What are your plans for refrigerator, freezer?, water heating system?
We have a Bosch on demand water heater (LPG) that I installed from HDep about 12 years ago. It luckily does not need electricity. It has a standing (small) pilot light (pizo igniter - like a BBQ) and as soon as we turn on the faucet it sense volume and fires. Been pretty darn good.
We are not off-grid but try to conserve. Wood stove heat take care of 960 square feet.
Lastly I was skilled in LPG and somewhat proficient with electrical but there are many nuances to Solar....Been following this forum for quite awhile, lots of very sharp folks contribute. I would just say read reviews of equipment that others have purchased to avoid being misled as to what a particular item will do.

We are getting 68%-75% productivity from our modules that are Jinko 72 cell premium 320w. You'll never get full charge but still have to do the math to be safe....That's one thing I never knew when beginning this last summer (I am a noob)
Click to expand...

Hi,

Thanks for the input. For now, just heating water on the wood burning stove. No fridge or freezer plans at all.
I will be doing the on demand shower though.
 
MichaelK said:
I had this discussion with the neighbor across the road some months ago, and I can outline what we talked about for your benefit. What you want is something that works now, but is incrementally expandable for your future needs. Here's what we discussed....

Start with a system voltage higher than 12V. The serious off-grid solar starts at 24V and reaches 48V. I have both. A good rule of thumb is if load never exceeds 1000W, then 12V is OK. If loads reach 2000W, then go with 24V. If loads exceed 2000W go with 48V. It looks like what you have now most likely won't reach 2000W, but might in the future.

You can start out with a smallish 24V system that won't cost too much. I'll throw in some math so you can update the numbers with your real-world findings.

You could start with a 24V battery bank made of four 6V golf-cart batteries. Assuming you don't want to deplete more than 25% per day, and gives you a day of autonomy before dropping to 50%, then you get.... 225AH X 24V X .25X = 1350Wh or 1.35 kWh.

Assuming you have 225Ah batteries you want to charge them at about 1/10 or 1/8C. So, 225Ah X 0.1C X 26V charging X 1.25 loss factor = 731W of panels. I can get 260W grid-tie panels for about 60$ each, so that would be 180$ for 780W.

You'll need a 24V charge controller that can handle that much power, which would be documented in amps. It works out to be....
(780W/26V) charging X 0.8 loss factor =24A. An Epever 40A would be fine. They cost ~135$ right now.

Lastly, you need an inverter. I'd say go with at least 1500W, because I've heard of people complaining that their 1000W unit couldn't start their frig. Look at this Samlex.... https://ressupply.com/inverters/samlex-pst-1500-24-pure-sine-wave-inverter
It has NEMA plugs, but it can be hard-wired into an electrical panel.

If you want to keep the 12V lighting, you can get 24V to 12V converters cheaply.
www.ebay.com

24V to 12V 20A DC DC Converter 20AMP 240 Watt Voltage Step Down Module | eBay

This converter can not be connected to solar panels or wind turbine directly. DC-DC Converter. Over temperature shutdown, Short circuit protection, Output reverse polarity protection. GOLF ADAPTER. 100% full stable output Current.
www.ebay.com

Keep in mind that this is MY idea of a starter system. If you want to power a frig, it might work, but you'll want to invest in bigger batteries and more panels before you get one. Eventually you will want bigger batteries, more panels, and a bigger inverter. These though can be added in 1 by one. Add propane heat for hot water, and either propane or wood to heat the home, and you will be quite independent.
Click to expand...
Good info.
Thank you very much!
 
IrishViking505 said:
Hi,

There is already lighting installed in the cabin - 12V.
Looking to stay below $2K.

Thanks
Click to expand...

That is probably doable but you are going to have to do most of what you listed while the sun is up and you are generating power from the sun. Once you switch to batteries, it will be tough to run all that stuff on battery power. Might work with a small generator.
 
Steps to calculate a solar system:
1. Calculate the electricity consumption per day
2. Calculate the system capacity
3. Find the right parts.

1. Electric consumption:

EquipmentTypical WattHourswatt hour/day
-Two (2) laptop computers - up to 10 hours per day continuous (+charging) for work.70w
Macbook Pro		201400
-Internet modem - on all day.6w
2-20wa, average 6		24144
-Dish Hopper Satellite Receiver with DVR - on all day.30w
According to this, the Hopper with Sling consumes about 22 watts with the Joey at 6.9 watts for a total of 28.9 watts.Feb 19, 2014		24720
-Two (2) 24" Flat screen TVs (only one on at a time) - on for up to 8 hours per day.35w24840
-Three (3) small 12V water pumps for outdoor shower, kitchen sink, and a back-up (all coming from 500 gallon rainwater tank). These will be used as needed, intermittently throughout the day.180w0.590
-Capability to charge three (3) cell phones each day.10w3x5=15150
-Capability to charge two (2) Amazon Fire Tablets each day.10w10100
Total:341w3,444= 3.44kwh

Purchase some smart plug to track your REAL electric consumption to have more accurate kwh data.

2. System capacity
Usable capacity:
For a typical solar system, you will expect 2 cloudy day between sunny day, thus your electric capacity should be 3.4wh x 3 = 11.2kwh

Battery Capacity:
AGM (Golf cart battery) usable capacity is 50%, never discharged lead acid battery lower than 50%. So you need a 22.4kwh battery bank. Suppose you will use 200A 6V battery, it's 1.2kwh/each, 22.4/1.2=19pcs
Lithium battery best cycle is between 20%~90%, which is 70% usable capacity, 11.2kwh / 70%= 16kwh, it's 13pcs of 100Ah 12v battery (13K USD) or 3 pcs of tesla battery ($3K USD)

Solar panel & Charger:
The solar panel should charge the battery from full discharge to full charged in one sunny day. Since we need 11.3kwh/per day, a 2kw solar panel will match the battery bank above. Try to grab some second hand one from craigslist at 4w/$, $500
Victron is great but epever is cheaper.

Inverter:
Above table shows the peak electric consumption is 356w, so a 500w inverter is a good choice. Remember, larger inverter will consume more electricity itself.

3. Parts
Seems $5K USD is a more reasonable budget..... The most expensive parts are the battery bank.
 
Irish...Check out the "About My System" link in my signature.
My system is almost set up to be exactly what you need.
The whole thing costs less than $1200

We also use a tankless on demand water heater that only ran $130 and has no need for power from the solar set-up.
Just needs D batteries and a 20lb LP tank.

Don't hesitate to let me know if you have any questions.
 
HARG Hunter said:
Irish...Check out the "About My System" link in my signature.
My system is almost set up to be exactly what you need.
The whole thing costs less than $1200

We also use a tankless on demand water heater that only ran $130 and has no need for power from the solar set-up.
Just needs D batteries and a 20lb LP tank.

Don't hesitate to let me know if you have any questions.
Click to expand...
very cool - thank you!

Liam
 
I’m interested to see what your progress is.

The ‘existing 12v lighting’ from 2006 has nothing on today’s LEDs btw. If you stay 12V, there’s a million things available for low cost low consumption lighting.

Your desire to stay under $2000 and the two year intentions you plan for makes lead acid batteries at 12V work for you- the dollars saved can buy many more panels and it appears daytime loads are important to you for work. So having less batteries than you might have ‘normally’ for 24/7 use could be used, and the extra panels will provide the work-hours power you need.

Sure a 24V system has advantages, but in accomplishing your goal as stated? At minimum an mppt charge controller and a dependable true sine inverter with battery cables will be $600-$700. Ten 100W panels ~$800. Cabling and fuses $100 or so. Six
deep cycle Group 27s at walmartha about $450. Run the laptops on DC (automotive) chargers to minimize inverter inefficiency loss.
That’s spending your $2000 but the expected loads might not be supported 100% by that system. In practice you might make it work, however. How many cloudy days you have can impact that negatively as well.

Run the panels at 24V with a charge controller that can take that input and charge 12V batteries. (Use a 12V-3V converter to power the water heater.) One $80 RV water pump will do all your requirements bt
Use as many 12V devices as possible so at night the inverter can be powered down.

I’m interested to know how far along you’ve come for your project! Or if you’ve increased your budget. Or if you’ve got something running successfully now and how you did it.
-thanks
 
Trukinbear said:
The manual one is nice in that where you didn't have hot water now you do without external power, but the electronic one is more of what you expect when you turn the shower on. I've had way too many too hot, and too cold showers.
Click to expand...
To get around that, I hooked up a Servo to the gas control, and a temp probe that reads once a second. The logic reads the output temp and adjusts the gas to compensate. Works pretty well. Also doubles as temp control like a real shower. Some like it hot, some don't.

The temp probe also operates as a freeze protection. It kicks on for a few seconds when temps get too low. Learned that one the hard way a few winters ago.

All that is to say, I should have paid a bit more and got a more fancy one, but I made it work.

/hijack over
 
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