Introduction: Backpack Mounted Solar Charging
Description & Materials
The purpose of this instructable is to give some insight into the best way to mount the Brown Dog Gadgets 5W solar panel onto a backpack for charging your phone/tablet/ipod/etc... while hiking or backpacking.
I have instructions and pointers for attaching to both a smaller (30 liter) daypack or a larger (65 liter) backpack since there are different challenges and considerations. All packs are different but there are enough similarities that adaptation of this procedure to other brands or styles should be relatively easy.
1. Splitloop Keyrings
2. Lightweight aluminum (non-load bearing) carabiners
3. Thin (1/8") bungee cords 8-12" long
4. 1" wide nylon webbing (optional)
5. Safety Pins + sewing thread/needle or machine (optional)
Naming conventions: "Panel" refers to the entire Brown Dog Gadgets 5W solar panel, "Cell" refers to one "window" or collection of actual solar cells that make up approximately 1/3 of the whole "panel"
Step 1: Determine the Best Fit for Your Pack.
The red pack is the smaller daypack and because it is much thinner it is impossible to get the panel to really sit on top of the pack so the best fit is to get as much of the panel to be on top of the pack as possible and have the rest hang down the back. You can see the size comparison in the third picture and the idea is to have one cell of the panel totally on top. This means we want the end of the panel with the cell closest to the edge to be attached closest to the wearers body and the USB port will be hanging down at the lowest point of the panel.
The blue pack is a much larger pack and you can actually get 1-2 of the cells to actually sit on top of the pack if you can position it properly as seen in the picture. Where the smaller packs will almost always want the cell end of the panel closest to the backpack wearer the larger pack might actually have trouble reaching the panel to a good attachment point behind the wearers head and might want the USB end to be closest to the wearer. This is how it turned out on my pack and you can see a couple trials on fitting the panel to the pack until I found the best fit.
So far I have found mounting the top as a fixed point and the bottom as a stretched tight attachment seems to be the best arrangement as you will see in further steps.
Step 2: Attach the Panel to the Top of the Pack
The red daypack has very limited availability of attachment at the top and the best location seems to be the load-lifter strap attachment. Note I have used the keychain split rings through the load-lifter attachment loop so as to not affect the function of the load-lifter straps. The panel is then attached using the lightweight (LW) carabiners through the gromets on the end desired.
The blue full sized pack has both load lifters and top cover straps in the same general area and while the load-lifter attachment points were covered the top cover attachment points were exposed so those were used to attach the top of the panel.
It seems to be best to have the top of the panel attached using a fixed location (non-stretchy) attachment so you can get a good stable location for the panel in relation to the pack.
Step 3: Attach the Bottom of the Panel to the Pack
The last step is to attach the panel to the bottom of the pack to any convenient/available attachment point. This is done using the bungee cord in my case so the panel will fit tight to the pack and not move around.
The red pack has a pair of ice axe loops at the very bottom and it seemed one 12" bungee cord would loop through both of them and attach to the panel to keep everything tightly in place.
The blue pack being much larger also has many more attachment points and the fixed attachment points midway down the pack were used but you can see in the first two pictures the fit seems a bit loose, I finally doubled up the bungee cords while adding the carabiner + keyring and it was a much tighter fit without being too tight.
With just a little preparation before leaving the solar panel can be quickly attached to the pack by using the keyring as an attachment point or the carabiners + keyrings and bungees to quickly stretch the pane tight for charging your cellphone/GPS/etc... while on the trail.
When initially gathering my materials I considered using the 1" nylon webbing sewn into fixed size loops or using the tightening clips also available to give an adjustable fit. Depending on the size of the pack and availability of attachment points this might still be desirable if other attachment points are already in use or don't provide as good a fit. The nylon webbing can quickly be looped into a test loop and pinned with the safety pins for sizing and later sewn into a permanent loop that will either attach with a keyring or carabiner to the pack and solar panel. This option turned out to not be needed in the case of my backpack but others might still find this a useful option to get an optimal fit.
Try to position the panel so it is as horizontal as possible without putting extreme tension on the cells and make sure you are clear of any clothing such as hats shading the cells as this will cut down significantly on your power collection.
If you are using your devices and it's not convenient to charge them while hiking for some reason you can always charge a battery bank that can later charge your devices instead. Many of these devices are on the market now with various power storage capacity so there are options for which ones might best suit your needs.