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1.
2.
Summer vs Winter sunlight
The maps above indicate the hours of summer and winter sunlight available per
average day that has sufficient intensity to enable a 12v solar panel to recharge a 12v
battery (defined as the hours of solar insolation).
Why is this important?
• Because a solar energizer with the right panel and battery size for New England
may overcharge a battery in Arizona unless it’s equipped with a voltage regulator.
Overcharging destroys batteries unless they have a regulator.
• Solar panels that are the right size for Arizona are too small for Vermont. This reduces
battery life by undercharging.
• And a solar panel sized for summer usage may be too small for winter. Putting it
simply, a solar energizer cannot fit all situations unless it has a regulator, a large
enough panel and large enough battery. To keep costs down low enough to sell “off the
shelf,” many manufacturers use too small a battery, too small a panel and no regulator.
1. Winter sunlight
—
(available per average day)
Solar Energizer Systems
2. Summer sunlight
—
(available per average day)
Location, season and angle of the
panel appear to be critical factors in
solar energizer success. Why?
The maps to the right depict the
differing hours of solar
insolation
for
a region in winter and summer.
Solar
insolation is the hours of sun available per
average day that has sufficient intensity to
enable a solar panel to charge a battery.
Three important things to note:
1. The summer insolation hours
(at
right)
for all areas are much higher
than winter hours. For southeast
Iowa it’s 6 hours in summer and less
than 3 in the winter.
2. The hours available are very
different depending on where you
live. Michigan in summer has 5
hours vs 7.5 in Arizona!
3. Ideally the solar panel should be
angled to meet the sun. That means
nearly flat in the summer and
nearly vertical in the winter—and
always face south.
So why is the identical energizer
sold in Michigan and Arizona?
It suits suppliers to keep things simple.
Yes, the panel and battery are probably
too small for Michigan (except in mid-
summer) and too large for Arizona
(except mid-winter).
That’s why many
farmstore solar energizers often fail.
And it’s the extra sunlight in the
Southwest that may damage the battery
in the summer by overcharging it.
(Premier’s PRS units are fitted with a
regulator to prevent this).
What powers a solar energizer at
night and on cloudy days?
A DC battery. All solar units have one
inside the case. The battery must be
large enough to supply the energizer for
several sunless days (we size ours for not
less than 7 sunless days).
21 sunless days from a 5 ampere-hr
battery and a 5 watt panel?
That’s what a Premier competitor
claims for their 0.5 energizer.
For the same size unit Premier offers
a 12 amp-hr battery, 10 watt panel and
suggests only 4 days. Explanation?
Few things are as misleading
.
A
normal 0.5 joule energizer consumes
50 milliamperes hr. So 21 sunless days
extracts 25 amperes from a battery.
The misleading unit with 1/5 the
battery and half the panel size reduces
pulse energy as the battery voltage
declines. In a day without sun the pulse
is only 0.25 joules, then 0.10, then 0.05,
etc. Not a pulse that will stop animals.
Why your location is important
when choosing Solar Energizers…
Location matters…
92 ENERGIZERS & SOLAR PANELS
www.premier1supplies.com• 1-800-282-6631
1. In the winter months—
A PRS should be close to vertical—to
keep it perpendicular to the sun’s rays
at 12 noon.
2. During the summer—
Should be slightly tilted toward the
south to catch available sunlight. We
prop one edge on top of the ground rod.
Winter Insolation
Summer Insolation