Solar Toby

Solar Turtle Press

Letters from "Solar Toby"
BARE KNUCKLE SOLAR

A regular feature from a Founding Father of the modern Solar Movement.

Here you will finds gobs of tips, techniques, devices and tons of wisdom, garnered over decades of work and exploration into the possibilities of Solar Power.

The Coil Noise Buster
Sun Angles
Burping the Batteries

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THE COIL NOISE BUSTER
10/25/09

Back in 1991, I was living in an unused railroad tunnel in Benson, Arizona. My entire electrical system was a 100 watt degraded solar PV panel, two Trojan 105, 220 ah, 6 volt batteries in series to make 12 volts. Along with this, I had a 250 watt Stat-Power inverter.

The inverter was a “Quasi-sine” wave design that had an output of 170 volts for one third of the cycle, then off for one sixth of the cycle, and then –170 volts for the other one third of the cycle, then off again for one sixth of the cycle. This eliminates the powerful third harmonic of the 60Hz. The inverter would run most of the loads under 250 watts, but it produced hum bars and popcorn noise on my TV and VHS tape recorder.

The problem was the fast rise and fall times of the chopped DC voltage. AM radios (that’s all you used to get in Benson) also did not like the inverter due to this switching. I needed a low pass filter like a two pole L-C circuit, but it had to be easy and cheap. After several tries, I used a 100 ft. extension cord coiled tightly in a two foot diameter circle (coil). This was tightly held together with plastic zip ties. I plugged the male end into the inverter and the other end I plugged into the TV and stuff. Presto! All the noise was gone!! The coiled extension cord acted like a transmission line, with continuous inductance and capacitance distributed throughout its coiled length.

I did write Home Power Magazine about this concept, but they never published it or contacted me back.

Yours in the sun,
SOLAR TOBY

Note: An L-C circuit combines an inductor (L) in conjunction with a capacitance (C) to form in this case a low pass filter. The longer the extension cord, the greater the effect.

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SOLAR TOBY'S SUN ANGLES

You can calculate the sun's angle for any day of the year by using the "Old Farmer's Almanac" by Robert B. Thomas, for that year.

Start by finding the latitude of the city closest to you.
Tucson's Latitude id 32°, 13 minutes and Phoenix is 33° 27 minutes.
This is the angle from the equator.

To find the minimum angle at noon, you also need the Sun's Declination Angle, found in the calendar pages for the month and day. Note that this angle can be S. (south) or N. (north) and is shown on the first and last days of the month in the "Declination" column.

This always changes in March and September, but not during any other month. The total declination is ( ) (theta).

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BURPING THE BATTERIES

Ever hear that strange “blorch” in the middle of the night coming from your lead acid batteries? That’s the sound of gas bubbles finally letting go of their positions on the lead plates of your batteries. This is not all bad. These rising bubbles stir up the electrolyte in the cells, which prevents specific gravity stratification of the electrolyte solution.

All lead acid batteries produce hydrogen and oxygen gases as the battery becomes fully charged. Before full charge, they do not outgas.

A well designed, temperature compensated, charge controller allows 10 minutes or so of gassing before the charging source is disconnected to prevent excessive water loss from the cells. “Hydro-Caps” uses a platinum catalyst to recombine these gases and drip distilled water back into the battery to prevent water loss and prevent explosive gases from escaping the batteries. (That’s a good thing.)

Unfortunately, when it comes time to add distilled water to your batteries, any bubbles present on the plates will displace the electrolyte solution, so it looks like you have more electrolyte than you really have in each cell. This is the number one cause of “sulfation” where the tops of the plates become exposed to air.

To prevent this, physically rock the batteries to knock loose the bubbles to get a good indication of how much distilled water you need to add to each cell. (I lift up four batteries at a time 1”, then drop them.) This is easy with 220 Amp-hour batteries connected together with #4 AWG stranded cables, but not so easy with the larger, heavier batteries bolted together with rigid copper tubing.

Automotive batteries do not have this problem since the vehicle’s motion (and the potholes) shake up the batteries for you.

Yours in the Sun,
SOLAR TOBY

--- More to come ---

Solar DIY, solar books, solar instructions

Child's Solar Oven
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This oven makes Natchos well, but I'm sure you can discover other uses, too.

Materials needed:

Cardboard box, around 1 cubic feet. (12' long x 12" wide x 12" high)

Enough aluminum foil to cover the inside of the box.

Elmer's Glue
Dark colored pot with lid
Large oven roasting bag with tie.

Step 1. Cut one side of the box so that the side folds out and down.

Step 2. Line the inside with foil, shiny side out, and glue in place.

Step 3. Put nachos, etc. in pot with lid in place. then put the whole pot in the roasting bag and seal it with the tie.

Step 4. Place box in sun with open side facing directly at the sun. Make sure oven bag with pot is in the center of the box.

If your pot has a glass lid, you can watch the cheese melt. If it is a solid lid, you will have to do some experimentation to see how long it takes for your solar oven to heat up hot enough to melt the cheese. You may be surprised.
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This entire article including pictures, is in my book, Solar Doghouse. You can find it on the "Publication" page.