• Doug Cook

Recharging Smartphones During Multiday Scouting Events – Part 1: Disposable Battery Ideas

There are several ways to use smartphones during multiday outdoor or Scouting events with your smartphone and have it fully charged and available every day.

Recharging a phone overnight in the tent offers the most convenience.

I present some ways you can have access to your phone in the daytime and recharge it in your tent at night. It incorporates the use of a USB recharger.


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For example the iPhone 5 has a 3.8V, 5.45 Wh battery that should offer 1440 mAH of capacity.  You will need much more than 1440 mAH to recharge that battery however.

Why is a higher capacity recharge battery needed?  Recharging using batteries solely is not a one to one transfer of energy.  All batteries give off heat during recharging.  This means a recharger must be able to supply more than the rated capacity of the battery undergoing a recharge.  A rating double your smartphones battery rating acts as recharge insurance to insure a full recharge.  It also helps to insure against the gradual capacity reduction that develops over time with rechargeable batteries.

I present a series of blog articles on recharging options.  I’ll start with the simplest and continue to renewable but more expensive solutions.


USBnoPowerRecharge

Gadget Recharging When You Have No 110V access

Smartphones and other gadgets offer convenient ways to capture images and video while out in the wild.  They often require overnight recharging that would use a 110 V line.  When these are not available we need another solution.

USB2

USB Port recharging

If your gadget can recharge through the use of a USB connector, you have options.  The symbol above is the USB symbol.  The connector that plugs into the power source looks like this.

USB rechargers

There are many USB rechargers that allow you to recharge your gadget.  The problem is that most of them require a 110V to recharge themselves.  An outdoor activity longer than one night requires a different solution.

Tekkeon MP1580 TEKCHARGE


Tekkeon1

Tekkeon2

The Minty Boost – A Build it Yourself Option

Building a recharger offers a neat and simple solution that can be more customized.  It offers an educational value for adult or youth in electronics building that wont be too intimidating. It also doubles the efficiency due to it’s circuit design.


ElectronicsMB

In Venturing, this may be considered useful towards the Arts & Hobbies bronze award & Outdoor bronze award (emergency preparedness).


VAHO

The first component functions similar to how the Tekkeon Tekcharge mentioned elsewhere in my Jamboree power series but you get the fun of building it yourself.  Adafruit supplies all the parts that you solder onto a circuit board.  This design will fit into an Altoids tin that you supply or you can order one for $2.00.


AdafruitMB

MB2

MB3

MB4

The recharger circuit produces some heat that can get hot which is expected.

Batteries recharging other batteries is inefficient.  There will be some energy loss due to resistance – up to one half of the energy will be lost to heat.

Costs

Minty Boost               $19.50 Altoids tin                   $2.00 (or free) D cell holder               under $2.00 (AA cell holder supplied in Minty Boost kit)

You can get D-Cell holders from your local or online Radio Shack.  Jameco is another popular electronic component supplier.

2D battery holder   http://www.radioshack.com/product/index.jsp?productId=2062241

Jameco 2D battery holder  http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_216390_-1

Results

In testing, 2 AA batteries brought an iPhone 5 that was 95% discharged to about 75% recharge state.  This compares to 4 AA batteries using the Tekkeon MP150 Tekcharge.  It appears the Minty boost is twice more efficient.

D-Cell output with the Minty Boost

Testing underway – results to be edited here soon.

AA cells are rated to about 2850 mAH while a single D cell can output up to 15000 mAH.

On the surface it would appear that a single D cell could replace up to 5.26 AA cells – lets round that down to 5.

In testing however the D cell did not seem to offer this great a capacity.  An explanation here might involve the observation by Duracell that:

  1. The AA format offers the greatest energy density.

  2. Hi loads decrease efficiency with more energy lost to heat and resistance.

Source (http://media.duracell.com/media/en-US/pdf/gtcl/Technical_Bulletins/Alkaline Technical Bulletin.pdf)

This compounds my previous observation that batteries recharging other batteries is an inefficient process.

Advantages

  1. AA cells can be bought nearly everywhere worldwide.

  2. This solution requires no electricity access.

  3. Recharging successful independent of weather conditions.

  4. Works for general travel power needs as well.

Disadvantages

  1. A 9 day event like a National Scout Jamboree would require 48 AA cells.


48AAs

Scouting embraces sustainability as we strive to be conservation minded.

This solution ends up being more expensive if you go to two of these multiday events due to the cost of disposable batteries.

I explore in another post a more sustainable solution using solar power and rechargeable options in my Part 2: Renewable and Sustainable Solar Ideas.

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