Instructables
Picture of Portable Phone Charger
My wife recently got the LG Lucid. Much to our dismay, the battery life was gone by about 3-4 in the afternoon from a full charge that morning. She loves the phone, however, so I thought a portable battery charger might be a good solution just in case she's in a store or somewhere without a car/wall charger. This is what I came up with - my 1st instructable! 

There are several of these around the net, but most people use an altoids container, a 5v voltage regulator and a 9v battery. I built one of these and it sucked. Because 9v bats only hold around 450mah at best, it charged the phone about 5%, which rendered it useless.  It also uses a female USB plug, which means you have to carry around a USB cord with you, which is extra hassle. I wanted to create something that used common easy to find parts, and was cheap to build. This whole project costs around $4 to build, and it charges the phone anywhere from 25-40% depending on the type of batteries you use.  
 
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Step 1: Parts list

Picture of Parts list
PARTS:

1x Battery box  - $1.99 (I saw it at another Radio Shack for $2.29, but my local one had it for 1.99)
4x AA batteries - $.50 (I went to the dollar store and bought this 8 pack for $1)
Cell phone cord  $1.50 (I found one cheap on Amazon, but make sure you get the one that fits your phone)
1A diode (these are very cheap if you buy them in bulk - probably in the 10 cent range). 

Tools
Soldering iron / solder
Heat shrink tubing, or you could use electrical tape I suppose

Alec Adams12 months ago
this actually works!! but soldering sucks!!
its_khal1 year ago
Nice one there TylerPA. But how long can it charge an Android phone? 4AAs? I'm thinking it wld just die in minutes. Pls, i'm a heavy phone user. I have a ups battery 12V 9amp i wish to use to charge my phone. Could you help with the circuits to go with it?
Do we have to connect red wires with diode???? and not the black ones.
it will damage your device...
you don't know?
i have own version of your phone charger but put a little interactive LED indicators!
wow what the project do you have?
how will i connect the diode?
You're really supplying about 5.4V to the phone, assuming there's a 0.6V diode drop. Either way, the statement that 6V will charge your phone more and more quickly is a bit misleading.

USB is standardized to 5V, and as such, I would strongly recommend against supplying anything but 5V to the USB circuit. You can probably get away with +1V or +2V over, and you're right that this will, depending on the regulation in the charging circuitry, charge the battery faster, but it also could cause much higher heat dissipation and stress your battery cell. Alternatively, if you don't get away with it, you'll fry the charging circuitry and need to replace your phone.
TylerPA (author)  warmflatsprite2 years ago
Incorrect. The voltage drop is only about .3V, I tested it before the diode and it was at 6.2 with fresh AA's, and 5.9V after. This is well within the manufacturers recommended voltage supply (4.9-6.2V) to the phone, which was double checked before I made this instructable.

Furthermore, I've used this charger many times over a span of about a year and a half and the battery life is the same as it was on day one, nor has it "fried" any circuitry.

Furthermore, it's common knowledge that batteries need a voltage rated at 1.5x (+/- 10%) the batterys' capacity voltage to effective charge it. On a standard 3.7V cell phone bat, this would place an ideal voltage charge of 5.55V, +10% would be a max of 6.105V, and a minimum of 4.995V which is almost identical to the manufacturers recommendations.
skrubol TylerPA2 years ago
Be careful throwing around 'common knowledge' like this..
For NiCad and NiMH that rule of thumb may work, but it does not hold true for Lithium Ion's. An unprotected lithium ion cell could catch fire or explode if charged to 5v. It would definitely vent and be ruined. Lithium Ion's max charge voltage is 4.2v.

Cell phones and most other devices with li-ion's built in have charger circuitry built in to the device. Typically this charging circuit is built around the USB spec for input voltage/current. USB VBus spec is 5v +/- 5% (or 4.75-5.25v) Anything about 5.25v could possibly damage connected devices (though I think pretty much any USB device is tolerant of 5.5v.)
Furthermore, fresh alkaline batteries with no load will put out 1.58v each, so your starting voltage will be 6.34v.
To further skrubol's comment, the term "charging voltage" doesn't really apply to Li-Ion and Li-Poly batteries, as there are multiple charge phases - some of which are constant current rather than constant voltage. The voltage that you're feeding your phone from your charger is the input voltage to your phone's internal charge circuit.

My original point is that while it may be safe to say that this design works for your individual phone, you have no way of saying that it works with all Li-Poly and Li-Ion charge circuits found in phones today, and as such it represents a hazard to novice would-be builders.
maxhuey2 years ago
".....the battery life was gone by about 3-4 in the afternoon from a full charge that morning"

Unless she talk for 8 hour straight, that phone should give you several days of use. There are a few things you need to do...

- while the phone is new, charge it up to full and use it until the phone is almost dead. do this for the first 3 charges.

- Kill all the apps running in the background, including default programs like life wall paper etc. Go to settings-application-running services to see which things you do not need running. Kill them.

- There are battery booster apps that will do this for you and they are free...

My LG goes for more than 2 days with just below average use and 1.5 days with lots of talking, text and net surfing. If you do the above and still not getting good battery life, then the battery is defective and warranty willl get you a new one.
Maxhuey, I have a Wal*Mart LG phone of some type - LG800GHL. I have not found anyone among my tech-savvy friends who can figure out how to disable the browser, the set world clock locations, or the keyboard tones. I would like to be able to turn it on and off or give certain commands without all the beeping and tone series. There are times I apparently pick it up wrong or something and even with the lock on, I suddenly find the browser eating up my airtime. I never browse! Is there a way to get rid of it or do I need to just shoot my phone?
standard lg process, menu, settings, application, then go to manage or running service to look for things you want to do. other function are in the settings sub menu. your phone company should be able to help you with stopping you browser from running by itself as this has been a real problem for many people, and the phone company love it too. unfortunately CSR arehard to get hold of, sometime waiting for hours to talk to one. If you were in my town(vancouver), it would be much easier for me to uust do it for you or, show you how to do it. cheers, max
maxhuey maxhuey2 years ago
Sorry I was using my phone to type so lots of spell mistakes....
I remember when my in-law's got the iPhone from Fido, he got billed with over $1,000 air time every month because his browser was turning on by itself every morning, showing him the stock market. Not knowing what to do, he simple hit a couple keys to turn the screen off (browser still running). After getting more than a couple $1,000 bills, and the battery drying up in less than 24 hours, we called Fido to have them block the data browser, but occasionally, the browser still popped up. In the end we decided to use a software, available free in the internet (http://www.unlockit.co.nz/unlockit/) to block the data completely. That was a couple of years ago and since the phone companies got lots of complaint, they decided to do away with pre-programming the handset with auto browser. You case might be different but still you should call your phone company to complain and ask for instructions to block data browser. Hope this help. max
wmiller42 years ago
I build one like this to power an mp3 player via USB while traveling long hours on greyhound - mine uses 4 D batteries and lasts about 200 hrs .
TylerPA (author)  wmiller42 years ago
Yes, that would be awesome - D bats hold the same voltage as AA bats, so input voltage would be the same, but you're right, the amp hours would be tremendously greater. My goal was to make something compact so that she could put it in her purse. 4 D bats would charge the heck out of something, but would be big and bulky.
you do have a point about the portability - I guess if space was no consideration we could get a motorcycle battery and build a big frankencharger - lol
e5frog2 years ago
Nice and simple, is that voltage recommendation valid for all USB-charging phones?

Cord seems to get a bit rigid with all shrink tubing.

I'm amazed over the super cheap things you seem to have over there, only $1.99 for a battery box with an on/off button...

There are 2AA chargers that also works for iPhone for just $0.99 including shipping on e-bay. Perhaps getting one of those, grab the circuit and put a larger bank of batteries in could be something...
TylerPA (author)  e5frog2 years ago
Depends on what battery you have and what it's rated for. My phone bat was 3.7v and manufacturers suggest supply voltage was 4.9-6.2. So anywhere in that range would effectively charge the battery according to them.

Yes, the cord is a bit rigid, but it doesn't bother me, it just butts up against the bat box when not in use.
ARJOON2 years ago
bit too dangerous to try on my phone, no regulation or constant current etc....
tutdude982 years ago
after the diode voltage should be about 5.1 - 5.2 volts??
It depends on the diode. A normal Silizium-Diode has 0.6-0.7V flow-voltage.
A Shottky-Diode has 0.2V.
So you have max 4x1.5V = 6V before the diode.
That makes 6V - 0.6V = 5.4V (for silizium) and 6V - 0.2V = 5.8V for a Shottky-Diode.

If you want to be sure you dont grill your device with a voltage too high, you can add a regulator (While ditching the Diode all together.
Simple but wastes energy: LM7805 (>13% loss)
Complex and more efficient: Omit the Diode and go for a Buck-down DC/DC-converter like http://www.linear.com/product/LTC1627 (around 5% loss)
But to be honest, that would make the project much more complex for every non-technician or -electronician.

TylerPA used the Diode as a simple, yet effective way to reduce the voltage. Call it a poor man's LM7805 :)



so with this i can charge phone just like using 9v battery and LM7805?
Yep. I made one a while back and it works great. The voltage of 4 fresh alkaline AA batteries is actually about 7 volts and with a 4007 diode it drops to about 5,7 volts. That is really to high but when you put a load on it it drops further down to around 5,5 volts which is within limits of the USB-charging.
4 fresh AA's usually gives a full quick charge and a slow trickle as the overall power drops. I've gone without power for a week on travels with this. Make sure to use a good diode, not a tiny little zener. They get too hot and burn on full charging.
TylerPA (author)  omnibot2 years ago
Yes, thank you. The little Zener diodes will fry. I tried one and it started burning my fingers within a few seconds. Kind of cool, but won't be much use here.
A zener-diode is a special diode with specially tailored breakdown-voltage. For normal forward-voltage is around the same as with a normal silicium-diode. See http://en.wikipedia.org/wiki/Zener_diode for details.
"zener" does NOT tell about the wattage. The 1N2846 is a zenerdiode and has 50 Watts... ;)

4007 or 1N4007 is the same as every 1N400*. The only difference there is the reverse-voltage. And the weakest is the 1N4001 with 35V RMS. So more than enough. Go and choose whatever 4001-4007 you find.
See http://www.pr-tronik.de/fileadmin/pdf/1n4001-em513.pdf for a listing of 1N4001-EM518 while the EM* are a continuation of the 1N4007-13.

And to be clear: 4007 is NOT a description of the diodes power dissipation-capabilities. It is simply a Model-name (1N400*) for a common diode with different (*1-7) reversevoltages. However you are right: The 1N4007 can dissipate 2.5W of power. But only if not covered with shrinktubes like you do :) So the power may be around 1-1.5W i think & guess.

The absolute normal standard-diode is the 1N4148 and has 500mW of powerdissipation max. THAT would be not enough for sure if you shinktube it and run a full highpower-charge.

I hope to have brought some clarity to the world of diodes. ;)
Yours, Orngrimm
Electronics Engineer, Dipl HF electrotechnics
TylerPA (author)  Orngrimm2 years ago
Yes, you are correct, it's a "poor man's" charger, which was my goal. There are far more advanced ways of building a cell phone charger, but it ups the cost as well.

Also, 6v is certainly not high enough to "grill" the device. And yes, the diode does drop the voltage just slightly.
TylerPA (author)  tutdude982 years ago
No, with fresh AA's, it would be closer to 6 to 6.2v, but as commented below, the diode as a tiny drop in voltage, so my output was around 5.9v. This is certainly within the range of "ok" regarding cell phone charging.