MintyBoost 3.0


I built a pocket size USB charger using a MintyBoost 3.0 USB charger, a 3.7 v, 2600 mAh LiIon battery and a built-in LiIon battery charger in an Altoids Wintergreen Mints tin. It can be used to recharge a cell phone, iPod or other small USB rechargeable device.

I’ve had‘s MintyBoost 3.0 kit and USB LiIon/LiPoly charger (this is v1.1) for a while but I never put them together. I liked the size of the Altoids gum tin of the previous MintyBoost versions I have built but I wanted a little more charging capacity than 2 AA batteries could provide. I wanted a suitable battery and enclosure that didn’t compromise charging capacity and size.

Using ladyada’s calculations for battery power, I decided to use a 3.7v 2600 mAh LiIon battery.

The battery’s capacity:
MintyBoost mWh = 3.7V * 2600 mAh = 9620 mWh input

The amount of current it can provide:
Output mAh @ 5V = 9620 mWh / 5 * 80% = 1539 mAh output (80% is the conversion efficiency)

Number of iPhone 4S recharges = 1539 mAh / 1430 mAh (iPhone battery capacity) ~ 1.1

The MintyBoost kit requires the soldering of a few components to a circuit board. I also made two mods to the internal battery charger. With this version (1.1) of the adafruit LiIon battery charger, removing the resistor R4 and replacing it with a 1K ohm resistor allows the internal battery to be charged at 1000 mA.

The internal battery charger has connections for external status LEDs. I connected current limiting resistors between the board and LEDs, then mounted the LEDs in holes in the Altoids tin. The green LED indicates that the internal battery is charging and the yellow LED indicates a fully charged battery. (LiIon/LiPoly charging tutorial at Adafruit Learning System)

The battery and circuit boards are mounted in the Altoids tin with double sided foam tape. I made a miscalculation in the height of the LiIon charger taped to battery – the cover won’t close when the charging cable for the internal battery is attached.

To charge the internal battery, a USB Mini B plug supplies the power to the internal battery charger as in the photo above. To charge a device, a USB Standard A connector is used. There’s also enough room in the Altoids tin for storing an Apple 30-pin to USB Cable.

MintyBoost 3.0 in Altoids Wintergreen Mints tin

Below are charging test results with an iPhone 4S starting with battery at 49%:

Time (minutes)      Charge (%)
0:00                           49%
0:15                           58%
0:30                           66%
0:45                           75%
1:00                           83%
1:15                           89%
1:30                           93%
1:45                           96%
2:00                           97%

If you are interested in the MintyBoost design process:

Google Video Chat on the Nexus S

Nexus S 'About phone'Last Thursday, Google announced video chat for Android with Google Talk. “Google Talk with video and voice chat will gradually roll out to Nexus S devices in the next few weeks as part of the Android 2.3.4 over-the-air update.” apogee82, over a, posted a link to the file for a manual update.

The file in that link is only for Nexus S phones upgrading from build number GRI40 – stock Android 2.3.3.

For the manual upgrade I did the following:Nexus S Google Voice Video Chat

  • Download the file, rename it and copy it to the root directory of the sdcard storage
  • Reboot the phone into the bootloader by holding the volume up button while pushing the power button
  • Use the volume down button to highlight recovery and push the power button to select
  • You’ll see a triangle with an exclamation mark in the center. Hold the power button and then press volume up and use the volume key to select “apply update from /sdcard” and press the power button.

Nexus S Google Voice Video Chat

Video chat works OK over WiFi. I haven’t tried it on a 3G connection yet. The Google Mobile Blog post says, “You can make calls over a 3G or 4G data network (if your carrier supports it).” I’ve read a couple of anecdotal posts that said it didn’t work on T-Mobile 3G.

Another improvement with the Android 2.3.4 update is that it seems to help the GPS in the Nexus S. The last time I used GPS Status and Toolbox, it took about two seconds to acquire a fix.

Android Macbook

Android running on Late 2006 MacbookI downloaded LiveAndroid, a LiveCD for Android running on x86 platforms from Google Code, to try on my Macintrash.

Currently I am running OS X 10.5.7 and Windows 7 (build 7100) on my Late 2006 Macbook (Core 2 Duo, T7200). I’m also using rEFIt as my boot manager. The Android LiveCD showed up as Tux on the boot screen and I got to the Android desktop with the message, “Please connect charger, the battery is getting low: less than 15% remaining”. I was running on AC and the battery was fully charged. I dismissed that warning and went into the console (alt+F1) to try to configure networking.

Android running on Late 2006 Macbook

The liveandroidv0.2.iso supports DHCP, so I tried to get the network running using the howtouse live-android instructions:

ifconfig eth0 yourip netmask yourip’s mask

e.g. ifconfig eth0 netmask

That resulted in ifconfig SIOSIFADDR: No such device

I also tried ifconfig eth1 but received the same message. I didn’t look at the startup log. What’s the use of anything