Solar Recharger for iPodTouch

One of the most important and available renewable energy sources is the solar power and it is believed that covering 4% of the Earth’s desert area with photovoltaic cells (cells that convert light into electric current) could provide enough electricity for the whole world. Using it may not be that easy, but solar power can be a viable option for mobile devices such as iPods, cell phones or PDAs.

This project utilizes a modified Adafruit MintyBoost Kit (a small USB charger powered by 2 AA alkaline batteries), a 3.7v 2000mAh Lithium Polymer battery, a Li-Poly battery charger and a solar cell, both from Sparkfun. The solar cell’s maximum capacity is 5v at 100mA in bright sunlight and it is used to make the whole device as compact as possible; a bigger cell could be used if faster charging is required.

The problem with the original MintyBoost is that the two AA batteries, if used to recharge an iPodTouch or an iPhone, are discharged pretty quickly so these have been replaced with the Li-Poly described earlier. The MintyBoost kit used in this project has a JST connector which connects to the Li-Poly charger circuit. The solar cell is connected to the charging circuit using a two pronged connector (you can also use another JST connector). The solar cell is then mounted on the MintyBoost metal case using 2″ wide Velcro.

You charge the whole thing by leaving it in the sun. The charger has a red LED which lights up when charging. After completion, you simply plug in your iPodTouch, iPhone or another USB-powered device you want to use. The author names this project the MightyMintyBoost since it improves the old MintyBoost with higher capacity battery and solar power capabilities. Details and pictures in the link.

Solar Recharger for iPodTouch: [Link][via]

June 30th, 2009

LiIon Battery Charger

LiIon Battery Charger

Even though not much information is published about Lithium Ion Batteries, we find them more and more often powering our portable electronics. While their price sometimes can go pretty high, LiIon batteries offer higher capacity from less weight and volume and faster charging. Laptops, portable media players, cell phones, cameras, etc. almost all use the LiIon so there is a very high probability to recover the battery from a damaged device and this way get all the advantages at a small price.

Like with other batteries, inside the LiIon type there are one to four cells connected in series, each at about 3.6-3.7V. Higher capacity is obtained by connecting series groups of cells in parallel. All is nice though until the battery gets empty, then the tricky part starts. Conventional chargers don’t work on LiIon and can even destroy them. There are some generic charges on the market but either they’re very expensive or they’re for small batteries.

Newer batteries communicate with the charger telling the settings to be used for charging. Even older batteries have a thermistor that monitors temperature and a protection against complete depletion. This being said, in this project is presented a DIY solution for a LiIon Battery Charger. There are some things you must know about the battery so that you can safely charge it.

First of all you must know the pin-out, you risk damaging the battery and/or charger if you connect it the wrong way. Then you must know the number of cells but you can determine this by dividing the battery voltage rating by 3.7V, you must also know the capacity and thermistor value. The charge current can vary between half and full capacity rating, the lower value the safest but the slower.

The charger presented in the link is based on application note AVR450 from Atmel. The project uses the AtMega8 microcontroller and it  features adjustable charging settings as well as Smart Battery Interface. Schematics and code for the Atmel are available as well as information on how to operate it. Good luck!

LiIon Battery Charger: [Link]

DIY Solar Charger for iPhone

Here is a multifunctional charger that you can use with your iPhone or iPod or many other devices. The main feature is solar charging using a 4.5V/100mA solar cell but it can also accept voltage input varying from 3.7V to 7V from a wall wart for example. Having a 3.7V 2000mAh Lithium Polymer battery inside it can also be used as a power reserve in your travels.

To build this you will need a Minty Boost Kit which is a USB charger and to this USB port you will connect the device who’s internal battery is depleted. You will also need a charger for the LiPo battery. The Minty Boost will be connected to this LiPo charger along with the solar cell.

Depending on the solar cell you will be using, you might need to put a diode between the cell and the charger to prevent the draining of the LiPo battery when the light is low. All it needs now is a case. All parts used are very compact, the solar cell is 3.7″x2.4″. Using a bigger one however will decrease the charging time.

It can’t take more than one hour to build it and considering the usability of this charger i wish you all good luck with your build.

DIY Solar charger for iPod/iPhone: [Link][Via]

March 22nd, 2009

Asus Eee PC car charger

Since I often find myself on the road with my battery drained out and because I intend to use my Eee Pc together with a GPS module as a navigation system I thought it would be a good idea to make myself a car charger. The charger would have to output 9,5 V 2.5A, and it would have to be able to maintain the output voltage constant over variations of the input voltage. Of-course there are lots of voltage regulators these days that would fit my circuit, but I chose to use the LM2576 because such a charger has already been build and tested here (also featured on Youritronics here).

Here is the schematic of the charger:

Eee Pc charger schematic

After ordering the needed parts I noticed that the  inductor is slightly bigger than I expected it to be, so fitting the board into a small box became a bit of a problem. But I managed to designed the board so that it fits into the chosen box. I also fitted a medium sized TO-220 radiator so the circuit would dissipate the heat even in continuous use of the charger. The pcb was made using the photo etching technique and I tried spraying it with a mix of colophonium and alcohol that would act as a soldermask. The result is not pretty but I hope it will protect my board from corrosion.

EeePc charger pcb

After the soldermask dried it was only a matter of minutes until I assembled and tested it. The charger works great, the output voltage remains constant over continuous variations of the input voltage. Now all I have to do is close the box, solder a cigar lighter connector and pack it into my arm rest compartment.

Asus eee pc car charger

July 20th, 2008

Lead Acid Battery Charger

Lead Acid Battery Charger

The project is dedicated to helping people build a high performance sealed lead acid battery charger. The project is also available as a partial kit with a custom made PCB. However, there is also enough information for you to build your own PCB (or use Vero board) or change the design to suit your own purpose.

Lead Acid Battery Charger: [Link]

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