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Portable USB Charger - Beginner's Early Project

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Kernel:
My first project will be a battery powered portable USB charger for use with my mobile phone which when running the 3G hardware under load to listen to music off YouTube runs out of battery rather quickly, and I'm way too much of a cheap arse to spend three digits on a phone with decent battery life. I've already spent 8 whole dollars on an extended battery pack, after all.

So I will build myself a battery charger or ten. The idea is to make something way cooler than the ones you get out of those new vending machines for $30, at less of the price, that you can fit 5 of in your pocket easily, running off of either AA batteries because they are available everywhere or a compact high mAh rating lithium battery which I could scavenge out of an old high end mobile phone. After all, they have them just sitting on the counter in a basket at Gold Buyers. Bonus points for building something which can be switched between the two with hot-swappable packs, even more bonus points for building something which plugs into a powered USB port for charging the batteries.

This is the board, or one like it, that I will use:
http://www.ebay.com.au/itm/10PCS-Mini-USB-5V-1A-Lithium-Battery-Charging-Board-Charger-Module-Hotsell-FV8-/130872106099?pt=AU_B_I_Electrical_Test_Equipment&hash=item1e7895dc73&_uhb=1
Anyone know of a higher quality board? Could I even build my own out of higher quality components copying the design directly, it looks pretty easy? Hell, I could even order 10 lots of each of the higher quality equivalent components, and replace the components of the boards directly. I will then be a good SMD solderer, woot.

It seems plainly obvious that it is, but I gotta ask: Is this a good first project for a beginner?

c4757p:
That's an actual battery charger board, meant to connect to a battery. A USB "charger" isn't really a charger, just a 5V power supply. Try something more like this.

But I don't get what the "project" is. It's already built!

mariush:
As c4 says... that's board is about charging lithium batteries using the usb port as power source.

You want to make a 5v usb power supply, which would basically allow you to connect a usb cable to it and to a phone and give the phone the power it needs.

If you want to use AA batteries to charge a phone, you basically need a boost regulator, which would take 1.5-3v and raise it up to 4.5-5v (which is what the phone expects to get from usb jack).

For example, you might want to have a look at LT1308 : http://cds.linear.com/docs/en/datasheet/1308abfb.pdf

Use the SEPIC design in the datasheet at page 10 and you'll get 5v @ 0.5A from 3-10v so you can use 2-4 AA batteries to keep the phone happy for a long time.
5v @ 0.5A is the standard power for usb ports on the computer ... with the plain boost design on another page in the datasheet this chip will give you up to about 400mA at 5v from 1.5v but with more input voltage it can go up to about 1A.

You may have to put a few resistors on the data pins on the usb jack to trick the phone into thinking the charger can do 1A or more... see the mintyboost  page about choosing the resistors to tell iphones that the charger is capable of a particular power : http://learn.adafruit.com/minty-boost/icharging

Kernel:
Ah, I was thinking it was the other way around, that the board was for taking batteries and putting power to the USB port... since it's actually a battery charger that gets its power from USB I think I'll get it anyway, or build my own, because I want to be able to plug my portable charger into somewhere using USB and charge the internal lithium battery that I will install as well as having the option of AA batteries.

A board like the LT1308 looks like a goer, might try building one and see how it goes. If it's a success I will build a few.

Think I'll follow your advice and place those resistors on the data pins to keep it versatile. Maybe I'll save somebody's day by charging their iphone...

amyk:
In other words you're making a battery-powered battery charger? :D

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