Drive Out
gear
gear SOLAR PANELS
Edited by MARK JOHNSTON
You’ve got the (solar) power
The technology for generating solar power in the bundu is so well-developed that
now is the time to get yourself a panel or two.
W
hen we first featured solar
charging systems for 4x4s in
2008, the concept was still
something of a novelty. At the
time, the exercise would have cost an arm
and two legs, and it was mostly the “greenies” who used it.
But those times are long gone. Solar power has become indispensable for
every­one who regularly goes to the bundu
for longer than a long weekend. Major outdoor chains now stock a variety of solar
panels and accessories. You are so spoilt
for choice that it could become confusing
and you could end up buying the wrong
equipment for your purpose.
That’s why we’re revisiting ways of harvesting the sun’s energy for your needs.
How solar power could help you
Running a fridge off a car’s starter battery,
simply doesn’t work. That’s why people
started installing dual-battery systems years
ago. In such a system, you use a second
battery (usually a deep-cycle battery) that is
also charged by the alternator to run a fridge,
camera or computer chargers and lights.
A dual-battery system with a good battery (that has been charged properly beforehand with a smart charger or a trickle charger plugged into a 220 V wall plug) is fine for
keeping your beer cold and meat frozen
for a weekend, but such a battery will also
only last about three days, after which the
chicken breasts might come crawling out of
the fridge.
The Achilles’ heel of this set-up is that
you have to drive to keep the auxiliary battery charged with the alternator. It’s no problem if you’re driving all day every day, but
what if you want to camp for a few days?
The alternator has to run at high revs to
charge the battery properly – game drives
and slow off-roading don’t cut it.
It’s here that a solar charging system can
save your bacon. Power generated by the
solar panel can be used to “top up” the auxiliary battery, which can keep your water and
lights running for days, or even indefinitely.
How do solar panels work?
When light shines onto a semiconductor
(usually silicon), it agitates the electrons so
that they start to flow and, voila, you have
a direct electric current. Repeat after me,
class: It’s the photovoltaic effect.
The brighter the sunlight, the greater the
efficiency of the solar panel. A solar charging
system is therefore more effective in Sossusvlei than in Sweden.
The time of day is also important. The
hours around noon when the sun is at its
highest is the best time, which is why it is
called the “charge window”. In Southern Africa the charge window is around 5½ hours
per day. It’s obviously shorter in winter and
when the sun is blocked by clouds.
Just remember that solar power is not a
ticket to unlimited power. If you’re unlucky
enough to get a week of rain in Vilanculos,
the Castles may become lukewarm.
Great, but where do I start?
A solar charging kit has three components.
The panel generates the electricity, the regulator is a small box that regulates the charging process and then there’s the battery,
where the power is stored. If you want to
blow-dry your cheese every day with a 220 V
hairdryer, you will also need an inverter.
The panel
Solar panels are rated according to the
amount of power they can generate, measured in watts (W). Typical sizes available to
the 4x4 market range from about 70 W up
to 200 W. Your choice is determined by how
much power you and the crew need in the
camp, and how much space you have for
a panel.
It’s not inside ... Storing your solar panel on the roof rack saves space, but don’t forget to move it out into the
sun if you park under a tree for shade.
64 DRIVE OUT november 2011
Power rating: To work out how much power your panel needs to generate, you have to
do a few basic sums.
Grab your calculator, a piece of paper and
a pen, and list all the accessories that you
want to run in the bush. We’re talking fridges,
lights, battery chargers for your camera and
cellphone, a laptop computer and maybe a
cement mixer.
Write down the power requirements of
each. It is printed on the manufacturer’s plate
on the product or in the owner’s manual. If the
power consumption is rated in amps, multiply
this number by 12 to get the hourly power
draw in watts, based on the equation Power
(watt) = voltage (volt [V]) x current (amps [A])
For a 40-litre fridge requiring 2A per hour,
the consumption is 12 (the standard voltage
for direct current camping appliances) x 2 =
24 W. Because this indicates the usage per
hour, you have to multiply by 24 (the number
of hours in a day) to get the total power
consumption per day in W, in this instance
24 W x 24 hours = 576 W per day. (Actually the consumption will be less – more like
380W for 16 hours – because the fridge’s
compressor doesn’t have to work as hard
overnight when temperatures are cooler
and little hands aren’t opening it to grab a
cream soda.)
Your fridge is by far the most power hungry accessory, although the number of lights
you use could also gobble up a big chunk
(especially if they are fluorescent lights and
not LEDs). Should you, for example, use
three 11 W fluorescent lights for four hours
every evening, you need 11 x 4 x 3 = 132 W,
not an insignificant number.
Chargers and laptops generally consume
so little power it’s almost negligible. Once
you’ve calculated the power requirement of
all your accessories, you could add it to determine the total daily power consumption:
576 W + 132 W = 708 W.
Back to the solar panel. Remember, it’s
only really effective during the “charge window”. To calculate the total power generated
by a panel per day, multiply its power rating by the number of charging hours in the
“charge window” (5.5 hours in South Africa).
An 80 W panel therefore generates 80 x 5.5 =
440 W, which is too little to keep the campsite
running indefinitely. You would ideally need a
130 W panel that delivers 715 W per day.
Panel size: It is all well and good to say you
need a 130 W panel. But will it fit into your
Jimny? Conventional solar panels made from
glass and metal can be longer than 1.5 m. One
option is to mount it under the roof rack. Or
you could buy two smaller panels rather than
one big one so it is easier to pack (two 70 W
panels, for example, deliver 140 W in total).
But there’s another alternative …
Flexible solar panels: Conventional solar panels are made from crystalline silicon
www.driveout.co.za
Wired for power. A solar power system consists of three parts: a panel (above), a regulator (middle), which
controls the charging process, and a battery (below), where the solar power is stored.
DRIVE OUT november 2011 65
gear SOLAR PANELS
Magic panel. You can roll up a flexible solar panel (above), which means it takes less space in the load bay. But
you pay a premium for flexible panels. This Steca regulator (below) uses LEDs to indicate the battery charge.
sandwiched between glass panels. Flexible
sun panels comprise a thin film of silicon
(amorphous silicon) bonded to a material
backing. Initially developed for military use,
they also offer a number of advantages for
the off-road traveller.
As it can be folded or rolled up, it takes
up less space in your 4x4. Even better, it
can’t break if you accidentally drop it or pack
it underneath the No 10 potjie.
So why, you might ask would one still buy
a standard panel?
Aha! Watt for watt, they are up to four times
more expensive than rigid panels. They’re
also not as efficient at converting sunlight into
electricity, although suppliers of flexible panels
say that the amorphous silicon still generates
electricity in low-light conditions.
The regulator
The regulator is the brain of the system. It
cuts off the power supply when the battery
is fully charged and performs the important
task of “stepping down” the current coming
from the solar panel from some 17 V to the
12 V for charging the battery.
Why is this important? If you pump 17 V
directly into a 12 V battery, you run a serious
risk of frying it or, at the very least, reducing
its lifespan.
Yet some people say you do not need
a regulator; according to them it’s a waste
of money or it wastes electricity and slows
down the charging process.
We don’t think you should risk it. Replacing a damaged deep-cycle battery will set
you back at least R1 200, while you can pick
up a decent regulator for only R300.
66 DRIVE OUT november 2011
What’s available? There are lots of brands
and types of regulators.
Most suppliers wouldn’t recommend saving a few bob on a cheap Chinese model.
Rather stick with an established and respected brand such as the German makes Steca
and Phocos.
More expensive models have an LCD
screen for displaying charging data, while
cheaper models have indicator lights to indicate whether the battery is fully charged.
Both do the same job.
The battery
As with a dual-battery system, you will need
to purchase a deep-cycle battery to store
the power generated by the panel. Such a
battery differs from a standard car battery in
that it can be totally discharged and charged
regularly. This makes them much better suited to the demands of a campsite.
Deep-cycle batteries are rated in amp
hours – the most popular sizes for off-roaders are 90 – 105 amp hours.
Obviously the greater this number the
longer the battery will be able to supply power.
Just bear in mind that the higher rated ones
are also physically bigger.
Balance the budget: Even though you have
a solar panel that delivers power, and a regulator watching over the charging process,
some battery management is still required.
Think of the battery as a bank account.
Money (electricity) flows in from the solar
panel. But the money also has to pay the
bills (power your accessories). If you want
a solar charging system that can supply
power indefinitely, you have to deposit more
money than what you withdraw.
Take an 80 W panel and a 40-litre fridge
as an example. The panel delivers 80 x 5.5 =
440 W per day. Using the formula power (W)
= voltage (V) x current (A), that means the
panel banks 440/12 = 36 A in the battery per
day. The fridge uses an average 2 A per hour
over 16 hours, a total of 32 A per day.
You therefore have a sustainable system that could run indefinitely, if the sun is
shining. If your campsite uses more than
36 A per day, it’s not the end of the world –
you will still get several more days of power
than if you didn’t have a solar panel. But
as the money coming in is less than the
bills being paid, the battery will ultimately
run flat.
Double up: It is also important to balance the
battery capacity with the amount of power
being generated. You can’t generate more
and more power and still only use one battery.
For example, if somebody wants to run
two fridges at his campsite, he has to double his solar panel capacity. But pumping
all this power into a single battery doesn’t
make sense. The battery will become the
weak link in the system, because it will have
to work extra hard to keep up with the demand from the fridges, while it lacks the capacity to bank power from the solar panel
fast enough.
The solution is to get a second deep-cycle battery. As a rule of thumb, pair up one
fridge with one battery, two fridges (or similar
load) with two batteries, and so on.
All together now
These are the building blocks of a solar
charging system. Now you have to put it all
together. But first a few things to consider ...
Wired: Most kits come supplied with wiring, but if you need to buy more, make sure
it’s good quality and thick enough (at least
4 mm2 panel flex cable) to avoid excessive
voltage drop. A frayed cable could spoil
your holiday.
Position, position: Where you install the
regulator in your solar charging system
is critical. Most kits come with a nice long
cable (10 – 20 m) so the solar panel can be
placed in the sun even while your 4x4 is
parked in the shade of a baobab.
Given that there will always be voltage
drop in the cable – and the longer the cable the greater that drop – it makes sense
to install the regulator as close to the battery as possible. Then the “prepared” current leaving the regulator only has to travel
a short distance to the battery, with minimal
voltage drop.
Off the shelf or tailor made? Armed with
the preceding information, you could safely
walk into a 4x4 or outdoor store and purchase a ready-made solar charging kit that
meets your requirements. Then it’s just a
matter of connecting all the bits when you
get to camp.
But should you get a double Christmas
bonus, you could consider a custom-built
rig for your 4x4 or trailer. It’s neater, as the
battery could be mounted out of the way in
the engine bay and all the wiring hidden from
view. A fitment centre could also ensure you
have the correct plug sockets (Hella, Brad
Harrison, etc) for your accessories.
If you want all the bells and whistles you
could get built-in inverters for 220V appliances, and even a battery monitor mounted
in the cabin so you can keep an eye on everything while on the road.
But make the appointment for your
Cruiser long before you hit the road to Selous, because installation could take forever
and a day.
Try one of these models
Panel only
PLAN MY POWER 80 W RIGID SOLAR
PANEL
Your uncle in the solar
panel business
SOLARFLEX 32 W FLEXIBLE SOLAR
PANELS
Build a puzzle
This is how to care for it
Keep it clean. Mud or dust on the surface of
your solar panel reduces the amount of light
hitting the silicon, lowering the efficiency.
Angle management: For optimum charging, your solar panel should be pointed
north and angled so that the sun’s rays
strike the surface at 90 degrees. Some panels have an adjustable leg or frame to lift it
up; alternatively, prop it up against a rock or
ammo box.
Remember fridge manners: Opening
your fridge excessively, filling it with warm
Black Labels or running it at -20 °C when
the outside temperature is 40 °C will cause
the compressor to work harder, using
more power.
Pack it right: With rigid panels the biggest
risk is that the glass gets broken, so use
common sense when transporting them.
Some people use sheets of high-density
foam for padding. If you have a rooftop tent,
you could store the panels in between the
folded mattress.
Even though flexible panels are much
tougher, you should still avoid bending it or
packing it underneath heavy objects.
www.driveout.co.za
Plan My Power have been specialising
in providing complete power solutions
for 4x4ers and campers for 15 years, so
they know what’s cutting.
What’s nice about their panel is the
fold-out leg that helps you angle the panel towards the sun. Their solar panels
are sourced from a variety of reputable
suppliers around the globe, and come
with a three-year warranty.
Price? R2 000 per panel
Contact? Plan My Power 011 678
5101; www.planmypower.co.za
Drive Out says: You could buy these
panels separately, but PMP will also
assist you in putting together the
complete package. They stock all
the components, including the superb Optima range of batteries.
Okay, 32 W will barely drive your cell­
phone, but you could link two or more
of these flexible panels to increase the
output (to 64 W, 96 W, etc).
When it comes to home time, the
panels can be stacked on top of one
other (the dimensions are 144 x 42 cm)
or roll them up like a pancake.
Price? R3 450 per panel
Contact? Safari Centre 021 595
3910; www.safaricentre.co.za
Drive Out says: They don’t come
with a storage bag, but Safari Centre can have one made up for you.
They’re also small enough to stow
inside some rooftop tents.
DRIVE OUT november 2011 67
Try one of these models
Readymade kits
BUSHPOWER 130 W SOLAR KIT
The in-your-face
solar panel
BushPower offer a range of readymade
kits, but their 130 W model is a big boy
that’s perfect for pairing with a trailer or
caravan (where the additional lights and
water pumps call for more power).
Their kits are available for different
budgets. Each system has the same
high-quality rigid solar panel, but the
prices of the accessories vary. You
could for example choose a cheaper
regulator with an LED display or a more
expensive one with an LCD screen, or a
shorter or longer cable.
Price? R4 378 – R5 244
Contact? BushPower 011 315 1400;
www.bushpower.co.za
Drive Out says: In a caravan, the bed
is the perfect place for stowing the
panel ­– preferably under the mattress
if you’re expecting a bumpy ride.
68 DRIVE OUT november 2011
SOMETHING DIFFERENT
FLEXOPOWER KALAHARI 162W 4x4
SOLAR KIT
Just call me flying carpet
Flexopower have earned the title as the
specialists in flexible solar panels. Apart
from providing solar equipment for expeditions to Mount Everest, they also supply the SA National Defence Force with
flexible solar panels. The Kalahari 162 W
and the Namib 81 W are new kits dedicated to the 4x4 market.
The Kalahari is a beast of a panel
– opened up, it is the length of a longjumping pit (295 x 45 cm), but it packs
away into a carry case the size of a
school case (45 x 35 cm).
The complete kit includes an 8 amp
Phocos regulator and a 10 m length of
4 mm2 of cable.
Price? R8 460
Contact? Flexopower 011 465 0022;
www.flexopower.com
Drive Out says: It’s the Victor Matfield
of flexible solar panels.
POWERTRAVELLER SOLARGORILLA
Ag mom!
This device is ideal for folk who don’t
own a fridge, but still want a solar panel
to charge their camera batteries or laptop. Roughly the size of an A4 exam pad
when closed, it has two solar panels.
It has two power outlets: the 19 V
socket charges most laptops (Macs,
which require 24 volts, won’t charge), and
a 5 volt USB port for cameras, cellphones
and other small electronic devices.
Two features that work well on
Power­traveller products are the rugged,
water-resistant casing (perfect for surviving bumpy off-road holidays) and the
good selection of adaptors that come
standard with each kit, ensuring that
your phone or laptop can actually be
connected to the charger.
Price? R2 200
Contact? Wintec Solutions 011 467
2360; www.wintecsolutions.co.za
Drive Out says: Not sure if it works
with your old Nokia phone or Dell
laptop? There’s a full list of available adaptors on www.powertraveller.com.