April 3, 2007

Project: MintyBoost

USB charger using AA batteries

These days, it seems I carry more and more things on these adventures that require battery power. Flashlights have always been on that list, but fortunately these lights are getting pretty small. Cost-wise, a digital camera is the much cheaper in the long run than one that uses film, but you need batteries. And for this trip, I'll also be taking along an iPod, to both store digital pictures from the camera and to help me with my language lessons. Potentially, I could need lots of batteries to keep everything running. I don't really want to carry all those, and replacements are costly even if they are available. So the best alternative is rechargeable.

My plan called for a solar panel on top of my backpack to recharge the batteries. For the camera and headlamp, it's just a matter of changing batteries, but not so for the iPod. Most commercial iPod power supplies still needed an AC outlet or another USB port to charge. The problem with those was would I be able to leave it unattended to fully charge, or worse, would I forget and walk off without it. I needed something that used the same batteries I was using in the camera and headlamp. After some internet searching, I found something called the MintyBoost on the Instructables.com website


For less than $20, I obtained a kit designed by 'ladyada', a MIT student, that uses two AA batteries to provide power to any USB device like the iPod. The charger circuitry and two AA batteries fit into an Altoids gum tim - so small and simple. The only problem was that I had never worked on an electronics project, even when in engineering school. The circuit board was ultra small to fit in the space available in the Altoids tin, but that meant precise soldering which I had never done.

The kit contained all the components I would need, except for the Altoids tin. (I bought Wintergreen because I liked the blue color) Plus, her online instructions are probably the most thought out of anything I'd seen - very professional. With a ton of close-up pictures with notes, and written instructions, she takes you step by step through the whole process.


To my utter amazement, I was able to finish the whole project in a couple of hours and it worked the very first time, just as advertised. No short circuits, every component was put in the exact orientation it should have been, and my solder joints must have passed the test. I couldn't be happier with this project. Since I was a complete novice, I ended up spending a bit more on new tools (but had an old soldering iron) and supplies. And I spent some extra time doing internet research on soldering technique. So in the end, this MintyBoost project cost me a bit more time and money, but now I have new skills that I can use on future projects. Looks like a winner all the way around.

And if you want to know how it compares to 'commercial' products out there, you are going to have trouble finding anything comparable. The reason is that older products that used removable batteries (single use and rechargeable 9V & AA) have mostly been discontinued. Corporate geniuses have decided that you will always have either a powered USB port or AC outlet available to recharge your external iPod power supply. Prices are actually coming down, between $40-$80, but still more expensive and less universal than the MintyBoost.

Initial tests at 'adafruit.com' showed a full recharge using alkaline batteries. I'll be using 2x2500 NiMH AA batteries, over four times more power, which should give me a considerable increase in hours listening to my iPod. I'll let ya' know.

And for those weight conscious folks out there, without batteries it weighs ____.

Links:
Instructables: MintyBoost
ladyada.net: designed the MintyBoost
adafruit.com: sells MintyBoost kits