Step 1: Estimate your power needs

The first step in creating a solar power system for hiking & research expeditions, is to estimate your total power needs, and choose a solar panel to match. Following is a table of the Watt-Hours needed to fully charge various common electronic devices. Watt-Hours is a measure of a battery's capacity.

Next, decide how often you will need to charge your various devices. For example, if you want to charge your digital SLR camera while in remote wilderness, and you know that under typical use, you get 3 days from the battery before it needs charging, then your needs are 15 WHrs over 3 days = 5 WHrs/day

To complete this example, we'll add the need to charge two AA batteries each day for a GPS unit, and an iPod every other day. Total daily power needs: 12 WHrs

For portable applications like research expeditions, we like to be conservative when estimating the power production from solar panels. It is nearly impossible to get ideal exposure for a solar panel when it is simply strapped to your backpack, draped over your tent, or spread out on the ground. So, solar power production may be only about half of what a properly engineered roof-mounted system might be.
Following are reasonable estimates for the various PowerFilm rollable panels (these are the lightest flexible solar panels available). These performance numbers are for the summer months May-August...

Based on this table, we can see that the smallest panel (R15-300) would meet our needs, minimize costs, and minimize size & weight to carry. Remember that this is our power budget, and therefore we must live within this amount.

Step 2: Choose a power storage battery & conectors

Next is to choose a battery pack to store your solar power. It should be small & light so as to not add any more weight to your pack than necessary. It needs to provide the connectors you need to charge all your devices. It should also store enough solar power to get you through times when the sun isn't as bright as we hope. We like to estimate at least equal to your daily needs. In our example, this would mean a storage capacity of at least 12 Watt-Hours.

Want to work direct from the solar panel, and not carry a power storage battery pack?
We'll have to see if the devices you want to charge will be able to do this. Read on...

In our example from above, we will need the following connectors...
USB: for our smart phone
AC outlet: for our camera & AA battery charger

Wait! AC power is not an option in these small power systems. AC power inverters will not operate direct from solar panels, and the small lithium-based power storage battery packs are not able to power even a small inverter. What to do?

Fortunately, we carry a wide range of lithium camera battery chargers from Targus, and these come equipped with 12VDC car adaptors in addition to AC adaptors. We also carry AA chargers that can operate from USB or 12VDC car sockets.

So, since we can get 12VDC output direct from the solar panel, and USB via a car adaptor, at this point it appears that we could choose to charge all our devices direct from solar and not include the power storage battery pack. But, should we go solar direct?
We almost always advise using solar-direct only when the trip is short, the weather forecast is positive (& reliable), and the solar panel is really only needed to top-up your batteries when needed.
Having the power storage pack provides an important source of back-up power for times when the sun is not cooperating. It also allows your battery chargers to operate at their best rates instead of limping along at whatever the solar panel is able to get from the sun. You will also be able to capture more of the sun's energy over the course of the day.

To help you select the most appropriate power storage device for your expedition, we've put together the following matrix of products taken from our Buying Guide page as the best matches for the PowerFilm solar panels in hiking & trekking applications...

For our example, we would recommend the Voltaic Pack. It's capacity is slightly larger than our one-day needs, and it is very small & light. It also includes all the USB & 12V connector capability we would need. Although the Voltaic Pack will not support a Targus camera charger for 7.4V battery packs, this function can be obtained by connecting the camera charger direct to the panel.
If the power storage pack is needed to drive the Targus charger for 7.4v battery packs, then the best option would be to choose the Voltaic Generator unit.

Need a laptop? Or need to charge more or bigger electronics?...

From the above tables, you can see that if your laptop computer typically lasts 3 hours during normal use before needing to be recharged (and remember that it is not good for lithium batteries to get completely drained), then you would need to replace roughly 50-60 Watt-hours with your solar panel. If you need 3 hours of computer use each day, then you must start with at least the F15-1200 panel. If you plan to use only 1 hour of laptop time per day, then a panel that will provide approx 20 Watt-Hours, such as the F15-600, or R-7 would be a good choice.

The larger solar panels (20 - 55 watts) are best used with the Brunton Solo battery packs.
The Voltaic Generator power pack is great for laptop use, and offers the Apple MagSafe connector as an option, but its input power specification limits it for use with only the PowerFilm R-14, F15-600, or smaller.
The PowerFilm panels can be daisy-chained together very easily using their optional RA-6 Daisy-Chain accessory, so you can combine panels to get more power. Remember not to exceed the maximum for the battery pack (one PowerFilm 3600, or two PowerFilm 28 panels is the maximum input to the Brunton Solo packs).

If you need to operate multiple computers, &/or have a variety of gear to keep charged, and need more than 55W of solar panel power, then you should look into the Outpost Power packs. These use the SLA battery technology, which makes them heavier, but also makes them the best solution for the largest portable needs. They are fully regulated, and can be connected to as much as 110 Watts of solar power.
The SLA batteries are also common to most parts of the world, and therefore are the best option for expeditions to Africa, Central America, Australia, etc., especially when camps are set-up for days or even weeks at a time, and a luggable battery pack is not a huge hardship.

See our complete solar laptop application note.

For most hiking & camping expeditions, one of the most common needs we hear about is AA battery charging for things like GPS receivers & radios. We advise customers to consider two scenarios...
1. Direct solar charging of AA batteries
2. Using an intermediate power storage battery

In the first option, the solar panel is connected directly to a DC-input AA battery charger.
We recommend the following equipment pair...
PowerFilm F15-300 or PowerFilm R-7
Targus Mini 12V DC AA Charger

The charger will operate any time the daylight gets bright enough, and will charge at the maximum rate of the solar panel in the light conditions. For example, this 5 Watt solar panel will charge at least 2 batteries per day from late spring through early fall. Most people will create a "battery rotation" whereby pairs of batteries are in the charger, charged & ready, in the device, & waiting to be charged. Every day, the batteries are changed & moved up the rotation. This way, charged batteries are never mixed with partially charged batteries in your device.
If you want faster performance, and more batteries per day, upgrade to the 10W or 14W PowerFilm panel. These will charge as many as 8 AA batteries in a summer day.

The second option allows you to store solar power during the day, and draw power when you need it, even at night. Besides having access to power anytime, an important advantage of using an intermediate battey is being able to operate the battery chargers at their peak rate, and not just at the present rate of the solar panel.
We recommend the following equipment...
PowerFilm F15-300 or PowerFilm R-7
ZAP! R07-PL2 Battery Pack
Targus USB AA Battery Charger

Or, for more power, combine the 10W panel with the Voltaic Battery Pack and the Targus USB AA Battery Charger.

NOTE: It is imperative that all batteries have ample airspace and be vented somewhat while they are being charged. If using a dry bag, be sure to leave an airspace, and preferably do not completely seal the bag.

Canon, Sony, Nikon, Olympus, Epson & others love to innovate and find ways to pack smaller batteries into their cameras while extending their operating time. Lithium Polymer & Lithium Ion batteries pack a lot of power into a small package, but they do have their drawbacks. Perhaps the most difficult is the lack of DC charging options. Each manufacturer provides a specific charger that only covers a certain number of their products, and are almost always designed for home use.

Fortunately, we have teamed with Merkury Innovations & Targus Digital to bring you a great range of AC/DC chargers for brand-name cameras. Click here to see the Universal Charger for Canon. From the Canon page you can find direct links to Nikon, Sony, Olympus, Panasonic, and others.

Because these chargers all offer a 12V car adaptor, all you need is to pair it with a suitable solar panel that will provide the power they need to charge your battery pack within one day. For hiking & expeditions, we recommend using the PowerFilm 600, R-14, or 1200.

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