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  • Doug Cook

Recharging Smartphones During Multiday Scouting Events – Part 3: Larger Scale Renewable and Su

In part 2 of this series, I describe ideas on solar recharging USB rechargeable gadgets on a small scale, most economical basis.

If you are willing to invest $350 to $600 or more, you can upsize your solar power plant.  Larger panels offer more power.  Newer solar cell technologies offer more efficient energy production.

Solar Power Station

I used this design at the 2005 National Scout Jamboree.

A Brunton SolarRoll 14 ($300+) connects to a circuit overcharge protection / solar controller ($35).  The controller prevents overcharging of the battery when complete.  This panel can produce a maximum of 12V @ 14 watts over 10 hours (14 / 12) x 10 = 11.67 AH  It’s shown draped on the edge of a dining fly in this image.

I have an AGM gel-cell battery ($25) to store it’s output.  I chose the battery based on what I need for replacements with an uninterruptable power supply protecting my computers at home.

  A typical gel cell has a capacity of 7.2 AH, 12V or more.

Size matters, the bigger the solar panel the more power you can generate.  The size comes at a greater $ cost, sometimes significantly $$$ greater.

Storage battery

If you use uninterruptable power supplies (UPS) at home I recommend you buy a battery that will also serve as a UPS replacement.  This allows you to eventually put the battery into service and keep one spare ready and in use as needed for your solar project.

Consider AGM gel cells if practical (source).  AGM stands for absorptive glass mat and are also known as valve-regulated lead-acid battery (VLRA), sealed battery or gel cells.  Regular addition of water is not needed.


Brunton Solar Roll 14                       $250 Recharge voltage controller          $  20 AGM Gel cell battery                         $  20

Commonly Available Technologies

Amorphous thin film is the usual technology used in panels that can be rolled up.  The efficiency of these panels is around 10.1 to 12.5 %.

CIGS (Copper Indium Gallium deSelenide) is another thin film technology with an increase efficiency to a range of 11 to 14% and are roughly double the cost of amorphous thin film.

Monocrystalline solar cells are in common use as well and come in panels with efficiencies ranging from 10.5 to 25% with most cells in between 18 to 24%

By using a 12V battery, you can use car charger style electronics to recharge your gadget.


  1. Higher power production abilities

  2. Should be able to recharge multiple gadgets on sunny days.


  1. Much higher investment costs

  2. AGM cells are heavy – too heavy for backpacking.  Lithium cell batteries may offer lightweight options but themselves add costs for large capacities.

Amateur Radio operators are frequent users of solar as well as other portable power sources. Images courtesy of Oscar Staudt (WB5GCX).


Multiple panels can be set up to collect more power.


Deep cycle batteries are designed to offer power over an extended period of time and can manage nearly full discharges and accept full recharges.  Standard automobile batteries on the other hand are designed to offer massive amounts of current / power in short discharges – necessary to start car engines but not ideal for extended use low current draws.  If you have ever experienced a dead battery while listening to the car radio during a weekend car cleanup, you’ve experienced the weakness that car batteries show when under a low current load over an extended period of time.

In part 4 of this series I explore a solution unique to the BSA’s National Scout Jamboree where recharging stations are present during daytime hours.

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