Solar-Battery Home Power – Part 1, by Jeff M.

So to begin with I must say that my move to a solar/battery system was rather supernatural. I had been pondering for a long time as to installing a generator for our home, or use the large portable I already own and can connect manually, or do nothing. I was constantly worrying about two things:  1. Where will I get fuel in a long term, serious societal event? 2. All generators make noise, most of them a lot, including mine.

I was trapped in a vicious circle of worry, especially with events of the past six years. I truly believe God put the idea in my head with a “stop-dawdling” message on repeat. That was August 25, 2021.

Getting all the disclaimers and such out of the way, I am a retired commercial electrician. I knew very little about PV solar power, actually nothing once I began educating myself and I realized how much I did not know and how many things that I had heard about solar and battery storage that were just not accurate. I also must say that I previously was not a “solar guy” My electrical background told me the scale needed to actually have enough power to be realistic in a home and that reality kept me away. Additionally, I realized the tremendous amounts of energy required to mine raw materials, transport, and then manufacture solar panels and lithium batteries. These calculations, if done honestly with current technologies, negate any lessening of our environmental impacts.

But, with that being said, I learned this on my own and believe it to be an incredible option as an emergency generator for your home. Your local codes and requirements will dictate what you may or may not do. I have electric utility service at my home, but my solar array is not “grid tie” with my utility provider. I do not have a commercially advertised solar system with grid tie capabilities. In other words, I did not build this to “sell back” electricity to the grid. That is not what this is. This system is a solar array with a large battery storage, 2 inverters and all the associated parts. Essentially “off grid” with utility backup. While we are blessed with a great life, the expense of a whole house generator (automatic) seemed unacceptable & unrealistic. I did not budget my project but I did price the main components before I began. I’ll total my costs at the end.

After getting out of bed with this new task implanted in my head I began reading, filtering out ads, promotions and marketers. I found two different young men on YouTube that I deemed reliable and knowledgeable. I also found many suppliers to buy different system components. Some readers will already know much of what my experience revealed, most won’t I think. The first thing I learned is there is a difference between “Grid-Tie” and “Off-Grid” systems. Many solar panels & other equipment, I found, are specially configured to shunt or shutdown electric current when the grid goes down in your home. The polar opposite of what I wanted to do. This is a safety feature so as to prevent backfeeding electricity into the local system, say after a storm where workers are repairing electrical lines. In a nutshell, your solar panels are still generating electricity and this would feed into the utility lines when their power is off without this feature.

The next thing I learned is that “real” solar panels are very large. I had only seen small 100 watt panels, generally in a small kit with cables and an inverter. So I bought 440 watt panels, 10 was the minimum order. I assumed I needed at least 10 regardless. These panels are approximately 42 inches X 82 inches X 1 1⁄2 inch thick weighing about 60 lbs. each. The Texas company I purchased my panels from had a strict protocol for accepting delivery as “damage during shipping” must be a thing. Ever the optimist, I was sure I would not experience a damaged delivery. But, two panels arrived with the glass shattered, however the panels are otherwise intact. I was refunded immediately for the two damaged panels, although they both work perfectly. Though I’m sure that their lifespan will be short.

During my education process I really wanted to just get going at this. Fearful of supply chain disruption stories I ordered equipment that I believed might be the items slow to ship or maybe unavailable. I ordered an inverter, a set of batteries from a US supplier, a set of Chinese-supplied batteries, and the solar panels. I received all this equipment promptly. The Chinese battery was flown to LAX and then trucked to me.

THE BUILD

Not being a writer nor an instructor, this is difficult relating my experience properly. I’ll do my best. I have a narrow, 7-foot space along the south side of our home. This space is unused and as I did not want the solar panels on my roof this space was my choice. I did a rudimentary sun angle test with one of the many apps available. I decided this would work but I would need to raise the panels off the ground due to shading. I installed simple deck footings and built a rack to mount my panels. I compromised on an angle that I felt would be best year-round. Ideally, the angle of your panels should change from summer to winter to maximize the power output. I compromised as I was not looking to power my home all the daylight hours. I needed decent power output to charge my batteries. Anything beyond that was a bonus. And I have been pleasantly surprised at the performance.

But I truly did not know how this would function at this time in my build. This is where sizing, electrical demand, and “what do you really need to power?” all come into play. I did a lot of guessing.

After installing the solar panels I wired these panels together with cables purchased online. They are simple snap connections requiring a simple release tool to disconnect as they are weatherproof. I also bought wire, connectors, plug ends and made my own cables in specific instances. This is optional as you can purchase any length cable. I drilled through the wall into my garage next to my existing electrical panel. I rolled these cables up for later use. Next, I bought a 125 amp, 20 circuit electrical panel {$87} to use as a subpanel. The purpose of this panel is to remove certain circuits from my existing electrical panel and reroute to this subpanel so that the selected circuits can be fed from the inverter. This eliminates any possibility to back feed into the grid.

Installing and wiring a subpanel should be done professionally. In simple terms, it can be dangerous for DIYers. I relocated all my circuits to this subpanel less the electric dryer, electric range, AC & water heater. My water heater was straight electric at that time requiring a 30 amp, 4,500 watt 240-volt feed. I have since changed my water heater to a Heat Pump water heater. This unit has the ability to function as a traditional electric water heater or in heat pump mode the unit only requires 4 amps, 450 watts at 240 volt. My solar can power this unit in heat pump mode easily.

I have a simple load monitoring system installed in my electrical panel, an Emporia Energy system. This allows me to monitor live, all my electrical usage. As this was all new to me, this system allows me to fine tune my circuits. This is not required at all. It is a gadget.

Next, I installed a 5,000 watt 240 volt all in one inverter. In simple terms, this inverter takes 48 volt battery power and converts it to 120/240 volt power usable in your home. The all in one designation indicates this unit, standing alone, will charge your batteries, control the power coming from your solar panels, and automatically power your home using combinations of solar, battery, and utility power. The inverter is user programmable and this was much of my education along with batteries up next. You can program the inverter with priorities such as solar first, solar with battery help, solar with utility help, and on. Many options.

With the installation of my inverter there are several safety items that are needed when wiring in the inverter. I have a 50 amp, 240 volt utility feed to my inverter and of course this comes from a breaker in my existing home panel. If you are completely off grid, obviously this won’t apply. The solar wires must be fused and have a disconnecting means, an on-off switch. The battery banks, most importantly, must be fused and also have a disconnecting means, a switch.

Next, I wired the 120/240 volt output from my inverter to the subpanel. This will supply the power to all the circuits I chose, basically my whole house. Connected my solar wires next along with battery cables to my battery banks.

BATTERIES

When I started this project the first subject I researched were batteries. I would not use lead acid batteries as they vent gas and do not last very long. Additionally, the ability to draw down a lead acid battery is limited. I quickly discovered lithium iron phosphate batteries, known as LifePO4. The batteries I bought, 2 sets, different types, are rated for 4,000 & 9,000 full cycles respectfully, 10 year warranty. The US based battery I purchased, 4 cells of 12 volt each to get 48 volts. Note, this inverter is a 48 volt based system, so however you configure your batteries it needs to be 48 volt into this inverter. All inverters are different and you can buy 12 volt, 24 volt or 48 volt systems. These batteries have an internal battery management system {BMS} preventing overcharge, overheat, and to prevent cold & hot weather charging.

To note here, These types of batteries cannot be charged below 32 degrees F nor above 120 degrees F. Very important! Some batteries have heaters. My batteries are in an insulated garage.The temperature range in my garage is about 56-87 degrees F so not an issue. The second set of batteries I bought from China is called raw cells or build your own. These are 3.2 volt cells so I bought 16 to get my 48 volts required and you have to build the unit. There are many sources showing how to do this. I felt it was easy considering the cost. On a capacity basis I believe this battery was 35% cheaper than the aforementioned unit. Again, this is not required, it’s optional, but an easy option for some of you. Fun too. For those doing this though, there is a balancing process that must be done to get the life from the battery pack.

WARNING

As an electrician I am aware of the power and dangers of electricity. These lithium batteries contain an incredible amount of energy. My little system has 24,000 watt hours or 24 kwh of stored energy! Our home uses about 500 kwh of electricity per month, average just for comparison. Also, even at 48 volts these batteries can be dangerous to people in certain circumstances. One big risk is shorting out the terminals on the batteries like dropping a tool or the like. Mine are covered in clear plastic for this reason. (See photos.)

The solar panels I have produce about 45 volts each. When wired in series, 10 panels produce 450 volts DC. This is also very dangerous. However, the solar wiring connectors prevent you from contacting anything energized. Much of this is common sense and staying within your skillset. Get help if you are unskilled or nervous with these tasks. This is a great system, but each individual has to be realistic with his or her limitations.

(To be concluded tomorrow, in Part 2.)