Funny how life works.
Yesterday morning, out of the blue, the power went off.
Even funnier?
I didn’t even know about it.
Until, that it, my lovely bride and brother-in-law wandered into my office and asked: “Did you know the power was off?”
I gave a gesture around the room: My super-computer (in the midst of an upgrade to an SSD) was still on. So were all four monitors that display what’s going on via the two dual HDMI video cards. The music was on. Zeus the cat was laying half up against the 750-watt electric heater *(which was on low). My halogen desk lamp was on. The scanner was still displaying blue ready for scanning. The duplex laser printer just had a page coming out of it.
“No, how would I know the power’s off?”
This, my friend, is the joy of a huge, massively over-built power system. I seem to remember there had been a single “beep” from the computer, router, and satellite uplink UPS power system a few minutes earlier. But the light hadn’t gone out.
Still, even though my office was warm and cozy while the rest of the property was getting more than 3-inches of rain, I picked up the analog old-style wired phone and called the local power company and reported the outage, although what most people may not appreciate is that while yes, Smart Power Meters may slowly morph our genetics, the Smart Meter would also stop reporting and power companies know that when blocks of meters go off-line together, there’s an outage.
Checking for Dangerous Backfeed
I turned off the halogen lighting and the heater. They’d been on since morning and I didn’t really need additional heat or light. and had Elaine follow me out to the power center.
I held up the 7-watt light in a plug-in light socket – one of those $2 parts that you can find at Lowes which is useful to see when an outlet is powered up, or not.
“Even though I don’t need to do this, I do it anyway,” I said, as the light was plugged into an outlet box labeled “Inverter 1 grid side” and then into “Inverter 2 grid side.”
As it should, the light stayed out.
“Do I need to know how to do that?” Elaine wondered.
“No, I just do it whenever we are at home to make sure the grid-interactive part of our system is still dropping the grid like it should. “ A note to the system log followed. “Tested system for no backfeed” and the date.
What’s backfeed and why does it scare the hell out of power company linemen?
Suppose you have a generator and the power goes down and you haven’t spent the money to put in a real transfer switch to physically disconnect your home from the grid in event a wire goes down somewhere down the road a ways.
People often times will plug a generator into the closest outlet in their home and if they are lucky, that leg of the 240 VAC power coming in will bring up a TV and the fridge and maybe some lights in the house.
Few bother to think about the downed line. A generator that’s plugged into house wiring will feed power back down the line to where it is broken.
It’s enough to kill an innocent lineman.
So apparently, Universe arranged our Thursday to make a major point about real back-up power systems.
NEVER NEVER EVER BACKFEED.
Now, about that Real Emergency Power System…
Hers is the shopping list I would go with for a really simple system:
Renogy 100W Mono Starter Kit: 100W Solar Panel+20′ Solar Cable+30A PWM Charge Controller+Z Bracket Mounts This will set you back $185 at Amazon. For another $150, add a second RENOGY 100 Watt 100w Monocrystalline Photovoltaic PV Solar Panel Module 12V Battery Charging as their 30-amp charge controller should handle the power of both cells.
Then you just need a good to great deep cycle battery and an inverter: Power Bright APS1000-12 Pure Sine Power Inverter 1000 Watt continuous / 2000 watt Peak 12 Volt DC To 120 Volt AC which is about $280 bucks.
Inverter School 101
There are two kinds of inverters: The cheapo kind are “modified sine wave” and the way these work, if you look at their output on a scope is it looks like those stepped pyramids in Mexico, rather than a smooth rise. It’s a stair-step kind of thing.
The pure sine wave is a better choice if you are planning to use a television, microwave, or radio gear because those “steps” may cause microwaves to hum oddly, televisions to have oddities to their pictures, and ham gear to hear “hash” on low bands.
But they are less than half the price of pure sine wave and if the batter is fully charged, you can microwave popcorn with either variety.
Battery Capacity 102
Now we need to talk about your battery capacity.
The most important thing to know is scientifically called the Peukert Exponent. Old Wilhelm (going from memory) came up with this law in the 1800’s. What he discovered was simply this: The faster you discharge a battery, the lower its effective capacity is.
For the science nerds, the details are in Wikipedia:
Manufacturers rate the capacity of a battery with reference to a discharge time. For example, a battery might be rated at 100 A·h when discharged at a rate that will fully discharge the battery in 20 hours. In this example, the discharge current would be 5 amperes. If the battery is discharged in a shorter time, with a higher current, the delivered capacity is less. Peukert’s law describes a power relationship between the discharge current (normalized to some base rated current) and delivered capacity (normalized to the rated capacity) over some specified range of discharge currents. If the exponent constant k was one, the delivered capacity would be independent of the current. For a lead–acid battery, however, the value of k is typically between 1.1 and 1.3. It generally ranges from 1.05 to 1.15 for VRSLAB AGM batteries, from 1.1 to 1.25 for gel, and from 1.2 to 1.6 for flooded batteries.[1] The Peukert constant varies according to the age of the battery, generally increasing with age. Application at low discharge rates must take into account the battery self-discharge current.
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