This adventure begins with a windstorm after which it took crews days to repair the severely damaged power lines. At that time we had been using a pair of old end-of-life batteries rescued from a Cummins diesel pickup truck connected to a conventional marine battery charger as our backup power. We waited all day as our freezer continued operations, powered by these old batteries. Towards dusk, I finally dragged out the generator to power the rest. Surely, there was a better way. That summer, I finally made it a priority to get solar panels installed up on the roof and the batteries upgraded.
We now have choices. Some of the backup power systems available these days involve slick turn-key solutions which neatly integrate all of the main components into a single opaque package that even the less adept user can manage. Some such systems are even available with solar panels already mounted on a trailer base in case one sets up camp away from the primary residence.
While package systems are generally good and helpful to achieve a noble end, they do not facilitate understanding which would at times be most helpful. Moreover, they tend to be exceedingly high tech, expensive and highly controlled by proprietary interests. For this reason, my focus is to round out knowledge dealing with modular components, so as to nurture a fundamental understanding that will be useful in a longer-term stuff-hits-the-fan (SHTF) event.
Energy
Stepping back a bit benefits one’s perspective. Understanding the progress of humanity these past two centuries is to reflect on our ability to harness energy stores in multiplying the effectiveness of human effort. Diesel enabled agricultural productivity beyond the imagination of farmers of the previous century. With modern equipment a single farmer is able to crop thousands of acres annually. Without petroleum resources the average farm in these parts was less than 100 acres and required a small army to cultivate, plant, and harvest.
Give some thought to what life would be like without the energy resources we now take for granted. Ask yourself, what steps can we take today to improve our future if the world as we know it suddenly changed to conform with the latest globalist anti-carbon injunctive?
Our self-reliant ability to produce and store energy offers a key to illuminating the future – to weather the storm – whatever form that might take. This essay, will be narrowly focussing on the basics of an electrical backup power system.
Understanding Electrical Energy
So that we have a common understanding I will begin with a bit of a high level introduction. Ham radio folks and the electrically adept can skip to the next heading.
Electricity is an invisible phenomenon that has the potential for doing work. It has the advantage of being able to distribute that potential to the exact location where that work is required. Distribution systems are often referred to as alternating current. Grid power alternates in this part of the world sixty times each second — 60 cycles. In other parts of the world (Europe) it alternates at 50 cycles per second. This alternating current (AC) is used whenever long-distance transmission of energy is required.
This sinusoidal wave of energy is characterized with transitions that are smooth and regular, as seen on an oscilloscope. When the transitions are choppy, boxy, and noisy, it is referred to as a modified sine wave.
Most household appliances are designed to operate using AC power at 120 volts. Heavy-duty appliances, like an electric stove will use 240 volts of alternating current. Also in the category of heavy-duty consumers are: deep well pumps, electric heaters, air conditioners, and clothes dryers. Heavy-duty appliances are beyond the scope of the present discussion.
Battery power does not use alternating current. We refer to this as direct current (DC). Most of your common automotive appliances are designed to operate on 12-volt DC. Class 8 ‘semi-trucks’, on the other hand, operate on 24 volts DC. By contrast, a typical flashlight battery dry cell is 1.5 volts, although these might vary slightly depending on the specific chemistry. A typical car battery is comprised of a series of cells in a single package.
Electrical energy can be described using ‘pressure’, electromotive force (E), using volts.
Amps represent the amount of electrons available at any one time, or current (I). You might understand this as the ‘thickness’ of the pipeline.
The product of these describe the power consumed (P) in watts: P = E * I.
The current relationship between voltage and resistance in ohms (R) is, I = E/R.
Conductors enable the passing of electrons. Generally, the metals of the periodic table are conductors. Copper is a decent conductor and is what is commonly used in wires and cables. Wires that are flexible are simply comprised of bundles of strands of thin wire. Insulators do not enable the passing of electrons.
The capacity of wires to pass electrons is commonly described using the American Wire Gauge (AWG). Extremely thick wires are described using low numbers: AWG 00 is very thick. #8 is the thickness typically used for electric stoves. #12 is typically used for 20 amp circuits. #14 gauge is for normal 15 amp circuits. Light duty extension cords are usually #16 gauge. And so on. The higher the AWG, the thinner the wire, the fewer amps it can carry without becoming hot. Useful engineering tables describing the characteristics of wires based on their gauge are available on the Internet if your user manuals do not already include these. Do note that internationally, wire gauges tend to be expressed in millimeters.
What is often overlooked is that even conductors do have resistance. When current is high and distances are great, resistance can become rather significant – even when using high-quality copper wires, as I will later describe.
Another concept to be familiar with is that of power consumed over a period of time: watt-hours, or kilowatt-hours (1000 watt-hours, KWH) which is the unit of measure that typically appears on our electrical bills.
Often when stating the capacity of a battery you will see a rating in terms of amp-hours (AH), the capability of supplying said amps over a period of time. Amp-hour ratings refer to a specific test that manufactures rate their batteries by. It might be that if a battery is able to supply 100 amps over a 20 hour test period, it will be considered a 100 AH battery. This is not to be confused with supplying 100 amps each hour of the 20-hour test – it is 5 amps each hour for a 20-hour duration – you do need to read the fine print when estimating your reserve capacity.
While these relationships are useful in understanding, do not let them bog down the conversation.
Storing Electrical Energy
The key components comprising such a backup power system are centered on the DC batteries. Battery technology has come a long way in recent times. But, the least expensive of these is still the standard flooded lead acid batteries that are commonplace in the cars and trucks most of us drive. Lead acid represents the most ubiquitous, time-proven, economical, recyclable battery technology available today.
While lithium-based batteries are used to power computers, cell phones, and high-priced electric cars, these tend to be very expensive. Their main advantage lies in the fact that they are lighter in weight than lead-based batteries. Lithium batteries are also extremely fussy in terms of their charging regime, requiring dedicated computer-controlled charge and discharge cycles. Lithium can work fine for a laptop computer and portable drill, but lithium can also be a part of some spectacular fires.
For stationary applications, the best bang for the buck is still based on the common lead-acid chemistry. The least expensive of these is the 12-volt vehicle starting battery. These batteries are optimized using thin plates to deliver high currents for a short burst of time. If the power grid goes down, we might expect that these could become a primary resource for something other than that car that you can’t get fuel for.
Flooded batteries are not just used in cars and trucks, they are commonly used in industrial applications and on sports fields. For applications that require electric currents for an extended period such as golf carts and forklifts, deep-cycle batteries with thicker plates are used. Thicker plates tolerate deeper discharges and are less prone to warping. Deep cycle batteries are typically 6 volts, with common examples including the Trojan T-105 and the Crown CR-235.
Figure 1: CR-235 6-volt deep cycle batteries with their caps off, while being watered. These can be chained in series to produce a 24-volt storage system, as shown.
Flooded refers to the fact that a simple liquid electrolyte is used. As such, you might recall that traditional car batteries require periodic inspection of the liquid levels and occasional top-up with distilled water. Deep cycle batteries require similar maintenance. The frequency of top-ups is largely determined by the number of discharge-charge cycles and the depth of discharge.
The electrolyte in a fully charged battery is pure water. In a discharged battery, it is sulphuric acid. Do not get this stuff in your eyes, on your skin, or on your clothes.
(To be continued in Part 2.)