The MintyBoost from adafruit Industries is an awesome little kit that nets you a USB charger that runs on 2 AA batteries. This is a great thing because AA batteries are available anywhere and together with the MintyBoost can be used to power most USB devices when you find yourself in a situation with no other source of power. As a volunteer providing emergency communications for organizations that are deployed to disaster stricken areas I have been in this situation before. Keeping critical communications links operational in the field is a major mission success factor. Having a highly portable source of USB power to keep cell phones working is a valuable tool for the first responder. There are, of course, many other uses for portable USB power. One of my favorites is extending the play time of graphic intense iPhone games while traveling.
This charger does more then just provide the 5 volts required to charge USB powered devices. The circuit incorporates a DC to DC boost converter that is able to draw power from batteries that may otherwise be considered "dead". Also known as a "Joule thief" this means you get more output from your battery power investment.
After building my first MintyBoost kit I immediately looked for a way to increase the charging capacity of the device. I noticed that a commonly available 4 AA cell battery holder will fit perfectly into a regular (pack of cards) sized Altoids tin with the MintyBoost. And the tight fit made for a very sturdy device with easy access to the batteries; which is important since the batteries are constantly being replaced.
Since the cells in a 4 AA battery holder are connected in series this results in an output voltage that can vary from about 4.8 volts to about 6.75 volts (for fresh batteries) depending on the type of AA cells used. The input voltage range of the MintyBoost is about 2-5 volts. So modifying the 4 AA cell battery holder to connect the output of 2 serially connected AA batteries together in parallel would result in about 3 volts for the MintyBoost input voltage but at twice the power capacity. The extra power capacity comes in handle with the power-hungry USB devices of today.
This battery holder modification is the primary subject matter of this instructable. I will also show how the modified battery holder and the MintyBoost are installed into the Altoids tin. Actual construction of the MintyBoost kit is not covered.
Thank you for all the great comments and feedback!
This charger does more then just provide the 5 volts required to charge USB powered devices. The circuit incorporates a DC to DC boost converter that is able to draw power from batteries that may otherwise be considered "dead". Also known as a "Joule thief" this means you get more output from your battery power investment.
After building my first MintyBoost kit I immediately looked for a way to increase the charging capacity of the device. I noticed that a commonly available 4 AA cell battery holder will fit perfectly into a regular (pack of cards) sized Altoids tin with the MintyBoost. And the tight fit made for a very sturdy device with easy access to the batteries; which is important since the batteries are constantly being replaced.
Since the cells in a 4 AA battery holder are connected in series this results in an output voltage that can vary from about 4.8 volts to about 6.75 volts (for fresh batteries) depending on the type of AA cells used. The input voltage range of the MintyBoost is about 2-5 volts. So modifying the 4 AA cell battery holder to connect the output of 2 serially connected AA batteries together in parallel would result in about 3 volts for the MintyBoost input voltage but at twice the power capacity. The extra power capacity comes in handle with the power-hungry USB devices of today.
This battery holder modification is the primary subject matter of this instructable. I will also show how the modified battery holder and the MintyBoost are installed into the Altoids tin. Actual construction of the MintyBoost kit is not covered.
Thank you for all the great comments and feedback!
Step 1: Tools and Materials
1 - Minty Boost
2 - 1N5817 diodes
1 - Altoids mint tin (about 3.75” x 2.5” x .8”) – any flavor
2 - 1N5817 diodes
1 - Altoids mint tin (about 3.75” x 2.5” x .8”) – any flavor
1 - 4 AA cell battery holder
There are a number of sources for 4 AA battery holders. I used one from Jameco Electronics and it's shown in the images below. It costs about a dollar and includes a square of foam tape that comes in handy when mounting the holder in the Altoids tin.
There are a number of sources for 4 AA battery holders. I used one from Jameco Electronics and it's shown in the images below. It costs about a dollar and includes a square of foam tape that comes in handy when mounting the holder in the Altoids tin.
22 Gauge stranded hookup wire (red & black)
Solder and related tools
Fairly hefty diagonal cutters
Stuff to insulate wires (Heat shrink tubing and related tools / Electrical tape)
1” wide double sided foam tape
Tools to cut thin, soft metal (Rotary tool and bit, small metal files)
Tools to cut thin, soft metal (Rotary tool and bit, small metal files)
Source:(www.instructables.com)
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