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.
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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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
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
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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.
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.
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.
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.
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.
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
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...
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.
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 :)
Also, 6v is certainly not high enough to "grill" the device. And yes, the diode does drop the voltage just slightly.
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.
"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