I have always been interested in electronics and DIY projects since I was very young. So when I saw an instructables page for the Minty Boost battery-powered USB charger, I jumped on it. Small Altoids-tin based projects are nothing new. Many people have come to utilize the low cost and ease of modifying the Altoids case. There have been dozens of interpretations of an iPod charger. However, most utilize a low current, expensive 9 Volt battery. The Minty Boost has well-composed circuitry that uses 2 AA batteries which are cheap and plentiful while offering 3000mAh each as compared to the 500mAh for a single 9V battery.
The Minty Boost kit is a small DIY electronics kit that is meant to be assembled inside of an Altoids chewing gum case. The concept is simple. On long trips or with intense use, iPods and other battery-powered USB devices don’t have the stamina we want. By keeping such an Altoids-tin charger handy, one can easily extend the battery-life of their USB devices by hours. On an iPod Video, you can amass 3 extra hours of power while using it on a Shuffle gets you 60 hours more. All this on cheap AA batteries is a blessing when power outlets are nowhere to be found.
The kit includes a pre-fabricated, high-quality printed circuit board that is sold by itself or with the electronic components. I opted for the complete kit with the PCB and parts so I wouldn’t have to hunt down all the parts on Jameco or Digi-Key. The kit assumes you have some soldering skills, but even if you aren’t handy with a soldering iron, the instructions are beginner-oriented.
The Minty Boost circuit board after I had assembled and soldered it.
Assembly was problem-free and went like most electronics kits: insert components keeping polarity in mind, solder, snip leads and test. As mentioned earlier, the Minty Boost uses 2 AA batteries to power the circuitry. The circuit takes the 3 Volts of the two batteries (2 x 1.5V) and runs it through a MOSFET-based boost chip. After the capacitors smooth the output voltage, the end result is 5 Volts at 100mA – USB spec.
The Minty Boost installed in the Altoids tin.
The next portion of assembly involves cutting a small section of the Altoids tin for the USB connector. Then comes fitting the PCB and battery holder. It was a rather tight fit and I spent a good deal of time fighting with the circuit board and cable. However, it finally found a snug fit, which is actually good so the board doesn’t move when inserting or removing USB cables.
The final, working product. Actually, there were no batteries in when I took this picture, but you get the idea.
I haven’t touched an electronics kit in a long time and the Minty Boost was a welcomed project. From opening the package to charging my iPod, only 20-30 minutes had passed. If you want to get more info on the specifics of the circuit and how it works, check out the amazingly detailed instructables page. The Minty Boost kit includes everything but the Altoids tin and runs for about $20. As for performance, the charger worked as promised on my iPod Nano. I might modify my charger a bit to add a small switch to the top of the case, as it is currently always on. However, the circuit probably doesn’t draw much power at all when there is no load present. You can see some more pictures of the Minty Boost in this flickr photoset.
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{ 18 comments… read them below or add one }
How much power does the Minty Boost provide? Will 2 AA’s fully charge the Nano? How long will the Nano run using Minty Boost power? Stats!
yeah it will charge a nano about 5 times. ipod touch, 1 full charge
I haven’t had the chance to charge it from a complete drain, but I think it can do a full charge on a Nano and a bit more.
Hi Paul
Where do you get the battery capacity figures of 500mAh for the 9V and 3000mAh for the AA?
The reason I ask is that rechargable batteries have a higher capacity than alkaline (disposable) batteries, yet the latest 9V NiMH capacity is 200mAh, and AA NiMH are 2700mAh, which is quite different to the figures in your article.
I would expect alkaline AA batteries to be 1500-2000mAh, though their capacity it typically not printed on the side like NiMH and NiCD’s.
Cheers
Jeff
It was mentioned on the instructables page, but yes I do know that it varies by type – alkalines, nicads, nihms, lithiums, etc.
D’Oh! There it is, right in the article. Hmm, will have to do some of my own capacity testing.
Yes, each battery technology has a different capacity for the same sized cell. Most photograhy guys are using NiMH over Alcalines for value and high capacity reasons. The NiCD technology has been left behind. The Energizer Lithiums have the most juice of any battery at the moment, but are only a one-time use.
Dude, it’s late there! Get some ZZZ!
thats awesome, ive been meaning to try it, it will work with any usb device
I would love to find a way to make this charge a cell phone, perhaps that will be my next project once my current project is completed. Awesome project Paul.
Hey Chris
That’s exactly what I am interested in this for, so I can use my Treo on the plane for longer.
You can use a USB charger cable for your phone. I have one for my Treo, and recharge from my laptop on the plane, but this minty boost would be a whole lot more convenient.
Being that I have never done any soldering, I am also considering one of these
If you are thinking about ordering this, wait until the next version. The creator has contacted me saying that it might not work on all devices just yet due to the lack of down pull on the USB D+ line. A newer version will be out sometime in the near future.
Can i buy one?
You will find a home-brewed, simpler and cheaper DIY solution at http://knowledgeaction.blogspot.com/2006/08/tech-tip-cheap-charger-for-ipod.ht . A trip to the local RadioShack and a few dollar bills will get you 4×2500 mAh (25 times Nano battery capacity). All iPods have an internal voltage regulator so this simple, batteries only arrangement will work. It can be used to recharge cell phones and other devices.
Actually, it’s more like 6 or 7 times the Nano battery capacity. The Nano has a 3.7V 400mAh battery, which is 1480mWh. On the other hand, 5V x 2500mAh is 12500mWh.
Then, 12500 / 1480 = 8.4 times as long, but since the internal regulator is maybe 85% efficient, you have to reduce that to about 7 times.
@Stefan:
Where is the “5V x 2500mAh” coming from?
2 NiMH cells are 2.4V. 2.4V x 2500mAh = 6,000 mWh, which is 4 times as long.
The actual voltage of a fully charged NiMH battery is much higher than the nominal 1.2V. In practice, 4 AA batteries come up to about 5.2 volts. I believe that’s where Stefan’s numbers came from.
As for Stefan’s comments, I am sorry it took me this long to address it. I had forgotten about my post here. Basically, I made a major assumption that the Nano must have a cut-off operating voltage. I assumed that the operating energy consumption is NOT 3.7V*400mAH*t but is something much less based on the voltage drop of V delta = 3.7 V – V cut-off. Therefore the additional energy consumption would be based on (5.2 – 3.7) V. This assumption, a pure conjecture on my part, could be completely wrong.
One thing is certain, if one takes into the conversion loss and the NiMH degradation over time, the actual additional time would be much less. But no matter what, the solution works like a charm. I have no idea how long the actual play time extension is because I have always recharged the NiMH batteries long before they ran out of juice.
If you will build it I will buy it. Let me know if you are interested and how much.
Can anyone advise me if Minty Boost will do the job for a Nokia 6110 which is equipped with a great (but power-hungry) GPS. the OEM wall charger for this cellphone is rated 5VDC / 650mA.
I am wondering if the pin 2 and 3 are signalled, cos I learnt that for some ipod and i phone, if the pin 2 and 3 are not signalle, the phone of ipod wont be charged even though Pin1 and 4 got 5 volt potential difference.
thx