Advanced USB Device Charger




With this tiny thing you can charge almost all devices that are charged via USB, like iPods or mobile phones, with only two AA-Cells!

Step 1: Having the Idea

So why should i build this?
The reason is quite simple: I am bored of empty batteries (Ipod, mobile phone) while I'am on the go. And the solution with the linear regulator like the "7805" is in fact very simple, but very unefficient, because: firstly you need a supply that provides about 3 volts more than you need for usb and secondly in most cases the difference between input voltage and output voltage is lost in heat.

The solution for the problem comes from Linear Technology. The most important compenent of the cicuit presented in the next steps is the "LT1301". This is a small step up converter for to build switching mode power supplys with only a few external components.

Step 2: Parts You Need

What you need:

->The LT1301 and a ic socket (8DIP)

->2 electrolyte caps WITH! low ESR (6,3V 100uF)

->one inductor with a very LOW! DCR (around 0,03R) with 10uH should be able to handle switching
currents at about 1,5 Amperes.

->one schottky rectifier like "SB130" or "1N5817" (important if you can't get one of the two proposed
rectifiers:low forward voltage drop, fast switching capability and it should be able to handle
currents of 1 Ampere.)

-> A switch(on/off), an usb connector, a circuit board, a LED with resitor (limit led current to 2mA!, don't loose your mA by pumping them throu the LED) and don't forget the battery holder

Step 3: The Circuit in Detail

What is important when building?

The input capacitator should be as close as possible to pin 6 (Vin) of the LT1301!
Keep all cicuit traces short!
Directly tie Pin1(GND) Pin8 (PGND) and Pin3 (Shutdown) togheter and connect it to ground.
Avoid long soldering times for to prevent destruction of components by overheating...

For the detailed placement of the components on the circuit board you can use your own creativity...

Step 4: Finished!

So now its done, but before connecting it to any usb device, be sure that it works properly! (the voltage should be 5 volts, the LED only should glow,etc...) When all is checked and you are sure that everything works you can (if you like it) start to put hot melt around it as kind of protection. In case you don't like hot melt you can put the device into a match box or everything you want...

on the left side of the picture you see an older version on the right you see the newer smaller, enhanced version

Some Technical data:
Input: 1,5 to 3 volts
Output: 5 Volts @ 200mA max. (really enough to charge an iPod mini or a mobile phone, trust me ;-) )
Watts and efficiency:
In: 0,95W at 2,5 V
Out: 0,875W at 5 V
loss: 0,075W
8 percent loss
92% efficiency



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    52 Discussions


    5 years ago on Step 4

    I think LT1302 will be good as it provides 600mA.I am trying to modify this project for use with this chip but i am not done yet, i will post if i achieve results.

    Does the phone monitor when to accept the charge? Or does the motherboard regulate the output?

    When building this, would it be better to 'shoot for a higher' voltage and amperage, say, 5v and 2.5amps and simply let the phone regulate the incoming current?

    Or does something on the motherboard adjust for current?


    5 years ago

    Is there a substitute for the 1301 chip or somewhere it is available in Aus


    6 years ago on Introduction


    can you show the perfboard configuration for me?
    i want build this one.

    ravi sibi

    6 years ago on Introduction

    sir, its so cool.... suppose if i want to improve the output current from 200ma to 300ma as well as 500ma, then what are all the modification should i done in the main circuit?? please respond because am doing a similar project with that ic....
    also i want to know weather it is possible to make 300ma from this lt1301ic..


    6 years ago on Step 4

    I agree 500mA would be helpful...


    6 years ago on Step 4

    Great guide!

    I'd like to use a similar set-up for powering other USB devices rather than just charging a phon and would need higher amperage (at least USB's standard 500mA), any toughts on how to modify your design to fit those needs?

    Tom Kazansky

    6 years ago on Step 3

    Will it work for HTC Wildfire S?

    Thanks for help.


    7 years ago on Introduction

    I really liked your stuff , I was searching for a subsitute to Minty Boost as it is expensive. But for me building your Circut is beyound my skills. As I am totally new to this world. I want to make these things on my own, I even tried to make a Solar USB charger but the Kit I got from a Hardware store was AC to DC, which I did not realise first. But every thing was done I connected the Solar cell and and My Samsung Champ phone It started to Charge but the fact is it was not charging In a Min. the screen dispalyed battery is full remove charger but the battery was still emppty. I am using a 6V 200 MAH. The circuit has 4 Diodes a capacitor 2 clay res. a 5v 7805 regulator.
    Please help.


    8 years ago on Introduction

    ok I haven't try this but was usb connector is the only option for charging phones and other gadgets, what about some other phones that uses jacks and sockets to charge? i hope you get what I mean because not all phones charges from Usb coonections, there are phones that uses different sockets and connectors for it to charge, can you show me a configuration in your circuit if i wanted to use jack and socket for my NOKIA N73........... your project was cool...


    Reply 8 years ago on Introduction

     yes, just use alligator clips to attach the (+) and (-) from the source battery in place of the (+) and (-) from the  9v clip


    8 years ago on Step 2

     why do the components need low ESR & DSR? what will higher levels do to the performance? 


    9 years ago on Introduction

    can 2 AA cells fully charge a celphone batery? many AA batteries are needed to fully charge a cellphone battery?=)

    2 replies

    Reply 9 years ago on Introduction

    Yes they can!
    Look a standard cellphone battery has around 900 mAh at 3,6 volts. 2 standard AA cells or AA rechargeable batteries have aroound 2,4 to 3 volts at 2000 mAh. the charger has an loss of 10%... This will be enough for one and a half charge!


    9 years ago on Step 3

    Can we use any other IC, cause i cant find it.


    9 years ago on Introduction

    are u sure it works??? my multimeter only reads 2.17 volts


    9 years ago on Introduction

    are you sure it works??? from my multimeter, i only get 2.17 volts