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Copyright © 1995 Virtual Publishing Co.
Solar power or specifically, solar photovoltaic (PV) panels, have become increasingly available as a power source. Solar PV is ideal for powering Amateur radio equipment because PV panels are almost always designed to charge 12 volt battery systems. Coincidently, most Amateur radio equipment is designed to operate from 12 volt power supplies.
Many Amateurs live in areas where the commercial grid power goes out frequently, or they live in areas that are prone to natural disasters that can cut out commericial power for days at a time. Naturual diasters such as earthquakes, floods, hurricanes, tornados, severe storms and blizzards all knock out commercial power systems. Because ham radio is often used for both primary and backup and communications in times of disaster, its nice to have a reliable source of power to keep your radios running. Additionally, many hams operate their radios away from commercial power systems during camping trips, hunting expeditions, boating and of course, the annual Field Day operating event.
You should not plan to use a regular automotive starting battery, especially for high power transmitters. Starter batteries are designed to put out a huge current flow for the few seconds it takes to start your vehicle’s engine. Their overall capacity is quite low and they do not withstand repeated deep charge/discharge cycles.
To use your simple backup system, you’ll need a battery charger that is designed to charge marine/RV batteries. Most automotive battery chargers available today are switch selectable between charging starter batteries and deep cycle batteries. Some hams successfully leave their battery on the automatic charger all the time. If you do this, be sure that the battery charger is an automatic model that will stop charging the battery when fully charged. In many instances, you can also leave your radios connected directly to the battery simultaneously with the charger. This will provide you with an inexpensive, reliable and ample power source during power outages.
If you must keep your battery inside, buy a gel cell-type battery. This type of battery uses a gelled
electrolyte, and is sealed so that it will not vent hydrogen gas nor spill acid inside your house. If you can,
put your conventional lead acid deep cycle battery in the garage or in a secure, covered and dry area
outside your house (keep it above freezing, or warmer if possible).
If you need to run power cables for very
far, be sure to use #4, #6 or #8 gauge wire. Connections between multiple batteries should be made with
#0 gauge wire or thicker. The photo shows a section of a bank of six deep cycle batteries bolted together
using a 1/8" by 1" aluminum strip. (During use, the battery banks is covered to prevent accidental shorts
caused by dropping tools or other items across the terminals).
If you power a typical 25 amp drawing HF transmitter along a
20 foot run of #8 gauge wire, you will be amazed to measure up to 1.5 volt voltage drops. Low voltage to
your transmitter results in other hams telling you that your frequency is unstable and and your transmitter
sounds chirpy!
Warning! Always fuse the cables running from the battery. If you encounter a short, your cables will
vaporize from the tremendous current stored in the battery. Your battery may crack and spill acid or even
explode. Treat your battery as a powerful electrical source that contains hazardous acid and which can
explode like a bomb.
If you wish, you can add a solar PV panel to convert sunlight into electricity and charge your battery. If
you add a small capacity panel (10 watt to perhaps 50 watts), you can connect the panel directly to the
battery. Always fuse the connection from the panel to battery and provide an easy power disconnect
switch. For small capacity panels, you can leave the panel connected to the battery all the time. The
charging current is small enough that it is mostly trickle charging the battery and will not cause harm if
continously charging your battery.
More solar panels means a greater current flow. If your cable run length from the solar panels to the batteries is long, you absolutely must use a fat gauge wire. If you do not use a low enough gauge wire (#2 to #8, for example), you will experience significant voltage drop in your cable, rendering your charging system ineffective. I use #4 gauge wire to carry 18 amps of panel current about 40 feet to my charge controller and battery bank.
If you add additional solar panels, you will need to add a charge controller to your setup. If your charging
current is too high, you will overcharge the batteries and evaporate the electrolyte. To avoid over charging
your batteries, a charge controller measures the batteries voltage. When the voltage reaches a fully
charged state, the charge controller disconnects the panels from the batteries. We use the Trace
Engineering 30 amp charge controller (shown in the photo).
It is available from Alternative Energy Engineering (800-777-6609) and is extremely reliable. Other brands of
charge controllers are available from AAA Solar Service and Supply. You can
adjust the voltage cutoff point to a value appropriate for your batteries.
By the time you’ve built up this much battery capacity, you’ll probably be thinking about converting your 12 volt power to 120 volt AC. You can do this using an inverter. Inverters are advertised in many sources, including auto parts catalogs and marine supply catalogs. Generally, you get what you pay for - I’d stay away from the lowest priced models. Most modertately priced inverters produce a square wave or modified square wave output. I have powered TVs, lights and computers on modified square waves without problems. There are some devices that really want to have clean sine waves. Sine wave inverters are available but cost a lot more.
Wiring, junction boxes and switch panels can all be purchased at local hardware stores. For fat gauge cabling, you might have to find an electrician’s supply store or a major city hardware store with a well stocked electrical department.
Solar panels are available both new and used. The best place to look for panels is in Home Power Magazine. See the Resources section on our Table of Contents page for more locations.
You can read a wide collection of articles about renewable energy topics in Home Power Magazine or visit their web site. Topics on renewable energy and sustainable living are also available. Charge controllers are also advertised in Home Power Magazine (800-707-6585) and are also sold sometimes in marine supply stores. To learn more about Home Power Magazine, send a blank email message to: hp.whats@homepower.org ; for a blank subscription form, send a blank email message to: hp.sub@homepower.org.
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Copyright © 1995 Virtual Publishing Company. All Rights Reserved.