DIY off-grid solar power + outdoor living + EV car charging.

[Ripple4]

Hi, i'm new to the forum, but have been reading MMM for a year now. I try save money so I don’t have to work my entire life. I like learning and doing cool projects too. getting these two facets of my personality to work in tandem instead of tension is a struggle, but in this project i succeeded i think.

One of the ways I want save money is with my DIY installed, hybrid solar power system. its hybrid because it can run off-grid in that it is using a large lithium battery as storage, and its hybrid because it can also use the grid, or a natural gas generator for power when the battery is flat. I’ve wanted an electric car and solar panels since i was a teenager, but it was out of reach in the 1990s when I started driving and evens 2000’s, only when one of my family members got a used Nissan leaf did I realize that it was now possible to do this. Then reading MMM I found he already figured that out and did the solar too. my system has elements of resilience built in so maybe in light of recent hurricane and wild fire electrical disruption issues, the OFF-grid/hybrid solar system is a ripe idea and ready for prime time. Google ‘solar plus storage’ and have a read for yourself.

The key parts of my solar setup are 1) used utility-grade solar panels for ~$.25/watt delivered. 2) Cheap and used lithium iron phosphate batteries. 3) Manual emergency power transfer switch. 4) high quality USA made inverter 5) Nissan leaf.

I could spill gallons of ink typing all the details out so I’ll only type the high points, but for the visual learners I made videos to document the build and function of the project. I have so few youtube views I’m 100 miles from monetization, I’m sharing only altruistically, so others can learn from all my mistakes.

https://www.youtube.com/channel/UC4vzgP4BO11aw8KBOuMHF4w

The design is taking advantage of the fact that ground mount solar panels have great usable space below them. So I put my screen porch under there. The size of the porch is great for entertaining at 12’x26’. The 16x solar panels are 295 watts each, and since they are used they should not be used for a grid-tied system, since they would not be approved by the utility, which requires only new equipment be used. In fact many decisions I made about this project are based around principals of independence instead of ease.

the flow of the system from panels to car are as follows: The direct current solar energy goes into a battery charger that is rated to a maximum of 7500w input, and 48v 100amp output, so the modest 4700wp (watt power max) I have does not slow it down. the program for lithium batteries is different from lead, so lots of hours of research are built into that. The battery is made up of ~14KWH worth of 26650 and 32700 LIFEPO4 lithium batteries, 1200 of them in total so far. These batteries do not have the risk of fire that LI-ION or LI-PO batteries have, so they are safer to have in the house.

The direct current power is then channeled to a magnum 4400w continuous split-phase inverter. This unit makes 120v and 240v power, good for running house loads and charging my electric Nissan leaf. The output of the inverter is sent to the garage to charge the car, but also to a 10 circuit emergency transfer switch that connecting into my homes' load panel. I had to select 10 120v circuits that can either have grid power or solar power. Things like my furnace, fridge, lights, garage outlets, sump pump etc. the inverter is 95% efficient taking solar power and turning it into AC power, but if it goes to the battery and then out to AC power, is only about 85% efficient. Which is still good for a round trip in a battery and converting from DC to AC. i have it cleverly wired up so that it acts like huge UPS (uninterruptible power supply) that prefers to use the battery, but when the battery is exhausted, it seamlessly switches to grid power, the lights don't even flicker.


To date, I’ve generated >1MWh of energy in three months and look forward to an annual production of 6-7MWh, that’s about $900 worth of power a year, or about ½ my electric bill. The simple payback is good enough to warrant it calling this a good investment. All in, I have $11,500 in both my 2012 M/Y Nissan leaf and the entire solar power system (the power of DIY!) The paid-off electric car saves me $4600/year (gasoline and car payment) and the solar energy $900/year. The $4600/year is based on a non-mustachian 60mile-60minute/day commute at 30MPG. So I figure the simple payback is less than 3 years. And since most of the payback is the car, and I’ve already had that for 16 months, I only have 13 months to break even in December 2020. there will be a party. In terms of ROI, that’s harder, as the Nissan leaf has battery degradation issues and also used solar panels will not last as long as new ones. So including a new Nissan leaf battery every ten years, in 20 more years, I’ll have banked $88K. But even if I buy another Leaf or perhaps a used Tesla Model S in 2 years, they will be down in price enough that I can still be in the black quickly.

focusing on the outdoor living side of it I am working now on making a concrete patio table that can seat 10 people with a gas fireplace in the center, reducing the weight is paramount. I am also seeing if i can get some solar-thermal benefits of the existing solar-electric panels to maybe get a craigslist hot-tub up to temperature. its going to be exciting trying!

Thanks for reading! GO SOLAR!

[Jon Bon]

Wow very impressive!

So in reading this you have a 5 KW system from 16 panels? Also you said your panels were used, so it is safe to expect production would be a bit higher using new pannels?

Lastly can you post your generation by month? I have found lots of this online but yours looks like a legit real world example.

Again impressive build, I am very tempted to do this myself in the next year.

[Dancin'Dog]

I'm glad you posted this.  I've been wanting to learn more about solar.  :)

[Wrenchturner]

Wow, looks like you did this for CHEAP!  Must be nice to feel 50% independent, anyway.  I'd love to feel 100% independent!

[zolotiyeruki]

That's a great story, and I love the idea of using the solar panels to shade the patio--it eliminates all the worry that comes from a roof-mounted system.  How much of the $11,500 was the Leaf, and how much was the solar system?  Where did you source the used panels and batteries?

[Ripple4]

Today was this posts day to shine!

Thank you for your story. I will take as an example for my family budget. I have installed the solar panels in my house and bought new tesla model S.

please also share your story. the more people that talk about how solar works for them the better.

Wow very impressive!

So in reading this you have a 5 KW system from 16 panels? Also you said your panels were used, so it is safe to expect production would be a bit higher using new pannels?

Lastly can you post your generation by month? I have found lots of this online but yours looks like a legit real world example.

Again impressive build, I am very tempted to do this myself in the next year.

I've read that panel yield degrades 1.5% per year. however I've seen a peak output of 4620watts on 4720wattpower of panels, not even in June either.

here is the solar output breakdown by calendar month, but my billing is mid-month so its not quite 1:1. but it shows the savings in magnitude. my number of $75/month is based on the average of summer and winter production and I only have the late fall and winter in these data. also in September my battery was smaller and the power would start to curtail at 11:30am once the battery was full so the energy readings are less than they could have been.

Wow, looks like you did this for CHEAP!  Must be nice to feel 50% independent, anyway.  I'd love to feel 100% independent!

I would not want 100% independence in this way. the 80/20 rule will come into play, that last 20 percent will take so much more effort and cost. however, I do have a new solar panel design I'm working on that will glue down to my driveway, provide 11.5kwp, and also melt snow with built in heaters. I have prototypes in process.

That's a great story, and I love the idea of using the solar panels to shade the patio--it eliminates all the worry that comes from a roof-mounted system.  How much of the $11,500 was the Leaf, and how much was the solar system?  Where did you source the used panels and batteries?

roof mounted system also need rapid shutdown (edit bad info out). the net cost of the 2012 Nissan leaf after I sold my old car (10 battery health bar) was $4900 (7900-3000). the solar panels have a 30% tax credit this year and I took that into that cost and the first year of savings, so to be direct, the cost to install the solar in cash outlay was $10,200. next year the solar tax credit is 26%.

For the used 26650 cells search eBay seller recyclagelra, ask for “low use” packs. I didn’t ask and got really degraded packs the first time.
For new 32650 cells look for Varicore or Liiokala 12 packs on aliexpress for <$38/12 pack, but be aware they overestimate the capacity by 30% a 6500mah is really 5000mah.
For the solar panels search eBay seller santansolar

Update:
The main addition to the solar install since my 11/22 post is that I am working on getting my whole house, “3-ton” central AC to run on it in preparation for a hot summer. I had initially planned to buy a mini-split system and run that on solar. But I found a way to modify my furnace and outdoor condensing unit with energy efficiency ECM motors replacing the old PSC motors to use 33% less power, total, so that it will work with my <5kw inverter. The trick is to reduce the starting surge current of the refrigerant compressor with a 240v soft starter and a tuned power factor correction capacitor.

[Dancin'Dog]

I subscribed to your You Tube channel and will check it out. 


We have a really nice large balcony with a concrete stamped floor that gets so hot in the summer that we can't use it.  I've been thinking about some kind of awning or shade cloth for it, but solar panels would be great.  Our HVAC is a hungry beast, and I'd love to start feeding it sunshine. 


GO SOLAR!  :)

[Ripple4]

I subscribed to your You Tube channel and will check it out. 


We have a really nice large balcony with a concrete stamped floor that gets so hot in the summer that we can't use it.  I've been thinking about some kind of awning or shade cloth for it, but solar panels would be great.  Our HVAC is a hungry beast, and I'd love to start feeding it sunshine. 


GO SOLAR!  :)

this system with batteries may not be right for everyone. If you read the most popular solarpaneltalk forum they really disparage battery systems even in the solar-battery subforum. but I also point to the secondlifestorage forum where people start with repurposed computer UPS boxes to learn and scale up from there. the UPS based system is nice because you could power a fridge or something in a power outage, and will reduce the utility bill right away. also people in RV circles do a lot with these same electronic parts, but they don't have the option of grid power when boondocking.

[Jon Bon]

Wow thanks for posting your honest to god real world numbers. That is the trouble I have with all of this so many calculators and such give you 100% best case scenarios which you might get 1 day a year.

Looks like running PVwatts calculator overshoots quite a bit to your actual numbers. Id be pretty angry if I installed based on their numbers and only got 50% of projected.

I attached the data from PVwatts 5kw system in Toledo Ohio. Looks like you are under approximately 25% or so of what they projected. Any ideas as to why?

 

[Ripple4]

Wow thanks for posting your honest to god real world numbers. That is the trouble I have with all of this so many calculators and such give you 100% best case scenarios which you might get 1 day a year.

Looks like running PVwatts calculator overshoots quite a bit to your actual numbers. Id be pretty angry if I installed based on their numbers and only got 50% of projected.

I attached the data from PVwatts 5kw system in Toledo Ohio. Looks like you are under approximately 25% or so of what they projected. Any ideas as to why?

 

That's all true. I sized this PV system to provide around 300KWH in December, which is what is needed for me to drive to work ~20 times and it made 253KWh, so its not as bad as the 50% number, more like 85%. not that big of a miss for my first install. Further, its a fundamental limitation of a battery based solar power system that not all the power will be converted into something useful. In fact its desirable that there is some waste because lithium batteries take a constant current / constant voltage (CC/CV) charge profile, and during the constant voltage part of charging the MPPT charge controller will curtail the power output in order to finish the CV portion of the charging without over charging. This is exactly what occurred in my data in September, the battery at the time was 7.5KWh (since upgraded to over 14KWh) and it was charged to 100% by noon or so, and I was not able to use it all for home loads, so it curtailed the power from the solar panels and all that sweet afternoon sun was 'wasted', left up on the panels and turned into heat. I'm not angry about it, I'm learning and improving the design. The power input in June, July and August 2020 will be colossal, and if I don't 'sink' it to the air conditioner it will be likewise wasted. I've already installed a second 10 circuit transfer switch and now run almost my whole house on solar when its available. Using timers and delay features on my washing machine I can have high load appliances turn on at 11am-1pm right when its needed to prevent power curtailment.

This is the advantage of a grid-tie system, the power is sent out the grid and used by someone else and the solar power system owner get their net metered value for that supply. However, that approach has its own limitations, like that I would need a 10 year contract with the power company I've got, and it fails to work in a power outage. In this project I'm highlighting a different way to do it that certainly may not be right for everyone, but one this is economical if done well.

[Jon Bon]

Again this is great information to have and I am really glad your being up front about posting it.

I am only interested in a grid tied system, as batteries look to add complexity and cost that I am unwilling to tackle (for now).

So it sounds like you are still in the process of fine tuning the system. I would love to see your spring/summer numbers when your panels can really shine!

[Syonyk]

How did you manage to get this to be NEC compliant?  Or does your jurisdiction not care/did you ignore that?  I can't imagine any DIY lithium bank meeting the (admittedly absurd) NEC requirements, or at least that an inspector would accept a list of technical documents as opposed to just a listing document.

If everything storage/solar/inverter related is portable, with the transfer switch having a plug, you should be fine - it's just not clear from the text how you accomplished that particular aspect.  I've abandoned my plans for a battery backed system, because the state "plans review" person has their own interpretations of NEC, and (from talking to people who do it for a living) regularly picks fights with if certain devices are "really NEC compliant" and will argue with professional engineers (NEC has the "or as calculated by a professional engineer" exemption clause almost everywhere).

roof mounted system also need rapid shutdown and trap heat on the roof.

Rapid shutdown, yes.  Trap heat on the roof, no.  In almost every sane install, you reduce thermal flux through the roof rather significantly as the roof is now shaded and, if you have a halfway decent gap under the panels, is cooled by convective airflow under the panels.  So instead of a roof being 130-140F on a 90F day, the roof (under the panels) is closer to 90-95F.  You have some radiative re-transfer from the panels, but the roof will be far cooler than it would be in the sun in almost every case.

Thank you for your story. I will take as an example for my family budget. I have installed the solar panels in my house and bought new tesla model S.

You... spent half a lifetime's worth of power on a car, and this is supposed to be budget friendly?  M'kay...  good luck with that.  $100k buys me about 70 years of power before I do a single thing with solar.

[Ripple4]

How did you manage to get this to be NEC compliant?  Or does your jurisdiction not care/did you ignore that?  I can't imagine any DIY lithium bank meeting the (admittedly absurd) NEC requirements, or at least that an inspector would accept a list of technical documents as opposed to just a listing document.

…

Rapid shutdown, yes.  Trap heat on the roof, no.  In almost every sane install, you reduce thermal flux through the roof rather significantly as the roof is now shaded and, if you have a halfway decent gap under the panels, is cooled by convective airflow under the panels.  So instead of a roof being 130-140F on a 90F day, the roof (under the panels) is closer to 90-95F.  You have some radiative re-transfer from the panels, but the roof will be far cooler than it would be in the sun in almost every case.

I did not have any problems. if your locality has draconian application of building codes there's not a lot you can do. we may say we 'own' our houses, but really its just a lease from the government and bank (if its mortgaged.) I've tried to be clear this is not for everyone. I did want to understand your point and looked into the NFPA rules and looks like they are provisional rules as of last fall and seem to cover batteries >20KWH.

I had a incorrect understanding of how rooftop solar installs work, I see there is good evidence that roof mounted solar reduces attic temps by a lot, and in fact are a major savings point due to reduced HVAC load, Thank you for correcting me.

[Ripple4]

In the original post it only got one sentence, a big part of this project was the outdoor living area that is created under the solar porch and the concrete patio table I wanted to put under it. this is an update on that part.

i've been developing the concrete casting technique since last november and its close to perfected. I wanted a 2" thick concrete patio table 10' long and 4' wide, which would have weighed 1300+ pounds if it was solid. So i created an each half of the table in an inverted mold with a technique were i cast the "table top" and sides with 60lbs of motar mix to create a solid skin and sides. i used the concrete thinning additive pouch to get it to flow like water.  Next I put in a steel driveway mesh panel to strengthen in. then i mixed 120lbs of mortar mix with 3 cubic foot of moisended shredded styrofoam and cast the 1.5" thick middle in 'foam-crete,' then another 60lb solid skin on the bottom. 2" thick, 5' long 4' wide and weights about 250lbs.

I originally stained the concrete 'desert rose' which is like a terra cotta color, but that was unpopular. so i trimmed in some grey concrete dye on the eating surface and then two coats of sealers.

the legs are 4x4 pressure treated wood with enough angle brackets and lag screws to hold up the 4x the weight. the wood is oil-painted brown with caster leveling feet. also the legs are in a "+" shape under the table instead of the normal "H" shape. it makes it so a person cannot knock their knee on anything. the tall back chairs are swivel rockers i bought on clearance last fall for $30/each. other special features are a fiber-optically illuminated glass checker board and under lighting, also a pop-up power strip with USB chargers. also i made adaptor to mount a 10" pizza oven to the fire table insert. we made some nice neapolitan style pizzas and they cooked fast, i made 12 personalized pizzas in an hour. so taking turns, a table-full of people can make customs slices and enjoy the company while it all cooks, pulling the chef into the party. check it out!

[BDWW]

this system with batteries may not be right for everyone. If you read the most popular solarpaneltalk forum they really disparage battery systems even in the solar-battery subforum. but I also point to the secondlifestorage forum where people start with repurposed computer UPS boxes to learn and scale up from there. the UPS based system is nice because you could power a fridge or something in a power outage, and will reduce the utility bill right away. also people in RV circles do a lot with these same electronic parts, but they don't have the option of grid power when boondocking.

Just found this thread. I just built a lifepo battery system for my camp trailer this spring. 4x180ah prismatic cells. I changed the wiring to run directly to the hybrid inverter(easun), and power the whole camper via the inverter or pass-through when plugged into shore power. Currently only have 200w of solar on the roof, but thinking of adding 2 more panels for a total of 400w.

In retrospect the biggest regret is not building a 24v battery/inverter system and just using a step-down for the 12v system. Oh well live and learn.

[bigblock440]

this system with batteries may not be right for everyone. If you read the most popular solarpaneltalk forum they really disparage battery systems even in the solar-battery subforum. but I also point to the secondlifestorage forum where people start with repurposed computer UPS boxes to learn and scale up from there. the UPS based system is nice because you could power a fridge or something in a power outage, and will reduce the utility bill right away. also people in RV circles do a lot with these same electronic parts, but they don't have the option of grid power when boondocking.

Just found this thread. I just built a lifepo battery system for my camp trailer this spring. 4x180ah prismatic cells. I changed the wiring to run directly to the hybrid inverter(easun), and power the whole camper via the inverter or pass-through when plugged into shore power. Currently only have 200w of solar on the roof, but thinking of adding 2 more panels for a total of 400w.

In retrospect the biggest regret is not building a 24v battery/inverter system and just using a step-down for the 12v system. Oh well live and learn.

Can you elaborate why you regret not doing 24v?  I'm waffling between 12 and 24 for a backup power source right now for a fridge and chest freezer.  I want to do 24v, but I'm only shooting for around a 1000 watt inverter and am having a bit of a time finding a 24v that small, or even 2000w.  Also, thoughts on using an inverter/ATS/charger combination vs all 3 components separately?

[BDWW]

It's just so much easier and ultimately cheaper. Almost all parts of the system are current limited. So 24v would allow for twice the power with the ~same component pricing.

The inverter I'm using is 1000w, so right now my camper is limited to that. I could get a standalone inverter that's larger, but then would lose most of the benefits of the hybrid inverter/charger. Shore/battery prioritizing, cutoff voltages, etc. Of course you could do everything piecemeal, but a big part of the appeal was having everything contained in one unit.

The BMS for the battery system is 120A max, realistically you don't want to pull more then 2/3 or 3/4 power through it if you want them to last. so 90A*12v (or 13.2 really) = 1080 (1188) watts max continuous pull from the battery. Same size BMS for 24v is virtually identical in cost, but 90A*24v =2160watts.  or 120*24 = 2880watts peak.

Same story for the inverter, roughly equal price for twice the power output/capacity. Also, because of the power capacity, the mppt is generally larger so you can run a more powerful solar array.

Cabling cost also lightens up significantly, as -again it's current limited - you can push twice as much power through the same size cabling or cut your cable size in half.

[BDWW]

As to the piecemeal approach it's certainly doable, but you end up with a smorgasboard of components. I originally was running deep-cycle lead acids of course, and had a pwm solar charger. It worked, but then adding an inverter, and a low voltage cutoff (in addition to the existing pwm controller, hall effect ammeter, shore charger and circuit breaker) and it starting to turn into a mess IMO.

The hybrid charger/inverter is an all in one unit, shore charging, shore passthrough, solar charging, inverter, and programmable profiles for prioritization, charging voltages and disconnects. So much cleaner.

[bigblock440]

Thank you, kind of what I was expecting.  My thoughts on the charger/inverter vs 3 components is reliability and ease of repair, I'd think it'd be easier and cheaper to replace one part if it failed than have to replace the inverter/charger or try to find parts for it, but I don't know if that's realistically a concern.  It would definitely be easier and cleaner to just use the hybrid inverter (same cost too), but I guess any way I go about it is going to have advantages and disadvantages and there will be things I wish I did differently.  I think I'm glad I didn't just jump into a 12v even though it'll be a smaller system, I think expanding it was on the back of my mind too, which I think would have pushed some current limits with 12v.  Thanks for confirming my assumptions.  I almost wanted to do a 48v system, but I don't think I need to go that big.

[Ripple4]

Can you elaborate why you regret not doing 24v?  I'm waffling between 12 and 24 for a backup power source right now for a fridge and chest freezer.  I want to do 24v, but I'm only shooting for around a 1000 watt inverter and am having a bit of a time finding a 24v that small, or even 2000w.  Also, thoughts on using an inverter/ATS/charger combination vs all 3 components separately?

I'd advocate for future plumbing, go 24v, with as high quality divorced components as you can buy.  its true that the actual solar panels are typically less than half the installed cost. you're right that 48V will narrow your equipment choices. The reason I say to go bigger right away is that is because doing some solar makes me want more solar, all solar. I find it rewarding to track the progress of my projects. Even with the heat bubble, my July-August power bill will be less than $70. May-June was $37. And knowing this, measuring that progress leads me to want more, a PHEV for my second car, when my furnace and water tank die they will be solar thermal or at least eletric. and if things go well, every east-south-west facing flat roof surface on my house will be covered with that beautiful black glass.

food for thought:
https://makezine.com/2020/07/09/fix-our-planet-electrify-everything/
https://makezine.com/2020/07/10/fix-the-planet-part-2-decarbonization-begins-at-home/
https://makezine.com/2020/07/15/fix-the-planet-part-3-new-power-nation/