Picture of Survival USB Charger: Use any power source to charge your smartphone
You forgot your power adapter for your cell phone? Or there is no electric socket available?

But you need to charge your smart phone urgently?

Let's build a USB Power Adapter, you can use anywhere! So you'll be prepared for an emergency!

Just connect this helpful gadget to any rechargeable battery and charge your phone. Even a AC voltage source like a table lamp will work!


Was machst du, wenn mal keine Steckdose in der Nähe ist oder du kein Netzteil dabei hast?
Wenn dein Handyakku schon unter 5% ist, du aber noch etwas Wichtiges erledigen musst?

Dann bau dir das Allround-USB-Ladegerät!

Damit kannst du überall dein Handy laden! Beim Zelten oder Fahrrad fahren!
Ganz einfach an Batterien oder Akkus von anderen Geräten anschließen und Handyakku laden.
Dieses Ladegerät kann man sogar an Wechselspannungen wie z. B. der Tischlampe anschließen.

Step 1: Parts list

Picture of Parts list
You will need:

- voltage regulator L7805CV
- rectifier, min. 1 A
- capacitor, min. 50 V, 0.1 µF
- capacitor, min. 50 V, 220 µF
- female USB jack, for example from an USB charger
- USB charger or plastic case
- copper plate or heat sink
- cable with alligator clips (or even better 2 alligator clips)
- soldering tin
- wire


Man braucht:

- Spannungsregler L7805CV
- Gleichrichter, min. 1 A
- Kondensator, min. 50 V, 0.1 µF
- Kondensator, min. 50 V, 220 µF
- USB - Female, zum Beispiel aus einem alten USB-Ladegerät
- ein altes USB-Ladegerät oder ein Plastikgehäuse
- eine Kupferplatte oder ein Kühlkörper
- Kabel mit Krokoklemmen
- Kabel
- Lötzinn

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ASCAS1 year ago
Awesome Idea! I voted BTW :D

Something bothers me a bit, you said "Just connect this helpful gadget to any rechargeable battery and charge your phone. Even a AC voltage source like a table lamp will work!". The 7805 is limited to 30v, why state that you can hook it up to an AC power source? By AC do you mean wall-warts?
Orngrimm1 year ago
2 things i wanted to point out:
- Charge everywhere... Well... Everywehere where you have 6 or more volts vailable (DC or RMS AC). A single solar cell wont work. So be avare of that to not to be disapointed.
- Some phones (like iPones) need the data-pins pulled to a certain voltage to negotiate that charge-cycle. Google first if your phone is one of those. If so, add a voltage-divider to the 2 data-lines to give them the correct voltage.

Apart from those 2 things, the idea is good and works.
Maybe you could combine it with a modded joule-thief and boost a low DC voltage of lets say a solar cell to 6V+ and feed it thru the charger then... But that would make a bit of loss, since you boost and then linear-regulate down again... Better boost to the correct voltage in the first place...
What you want is something like this, preceded by a bridge rectifier and smoothing capacitor as already shown in this instructable:

I have used exactly those before (and others from DX and also Aliexpress). They work... sort of. I had multiple faulty ones. Mostly bad soldering. Nothing a quick desolder and resoldering with proper geat cannot fix.
But the converter you pointed out is barely able to deliver the 1A continuously without overheating. So if you go in the range of 1A be sure aou add a heatsink to the 2 LM****
Haha indeed Orngrimm. Maybe DX was a bad example :-) What I meant was some sort of automatic step-up/down converter to widen the input range. In a survival situation, you never know what you are going to come be. Some sort of heat sink is always a good idea. Related to that: If this is a true survival power supply, go for military grade components. A lot of 'consumer grade' components die when the temperature drops below freezing. Potting the whole circuit in epoxy is also be an interesting route to explore to make it waterproof.
Personally, I would prefer something that I can shake or crank to generate power in a survival situation, but that is beside the point :-)
Good ideas there!
The range of power-generators start with solar, wind, Muscle (Hand-dynamo), dynamo on your bike, Thermoelectric generator, magnet-shaker, half-dead batteries, batteries not designed for your voltageneeds (12/24V)...

But remember to NOT cover the heatsinks in epoxy... Would render them useless ;)
Noise Maker (author)  Orngrimm1 year ago
Thank you for your detailed comment :D

Yes, of course you can not get energy out of nothing. Using a solar cell is a good idea and I'd like to try it out but I haven't got a big enough solar cell available.

As far as I know an iPhone hasn't even a normal USB Port, has it? I am not sure because I haven't got one but it's good that you told us that :D

That are good ideas but the project would get a lot more difficult for beginners. And if I'm honest I have never worked with low DC voltage regulators before (aren't they more complicated and expensive?)
Another thing to point out with these regulators: the current draw out is the same as the current draw in. This leads me to believe that the chips mainly just a self regulating resistor...
Thats correct. A linear regulator (Thats why they are called regulator and not converter) is a small circuit where a transistor greates this much resistance to make a voltagedrop just big enough to come from inputvoltage to the outputvoltage.
So yes: from the outside it is a selfadjusting resistor. :)
iPhones have a own connector on the phone-side, yes. But those cables often end in a normal USB-plug. You CAN (and normally do) charge iPhones on USB... the added circuit is in the adapter you connect to the iPhone itself.

The thing i was looking for, was the "MightyMintyBoost"... It is a "proper" DC/DC converter using the LT1305.
The magic to make it load a iPhone / iPad is described here:
http://timothyb.net/DIY_iPad_2_USB_Charger.html or www.instructables.com/id/Make-a-USB-iPhone-iPod-Charger-On-The-Cheep and many other places.

Depends on what you call complicated... the LT1305 needs 7 additional parts to the chip itself. So yes: It is more complicated. But i could post a 12V to 400V (DC) converter based on OpAmps and FETs and such stuff. But no dedicated IC there... Only off-the-shelf and standard-components... But it has all the bells and whistles attached like automatic frequency-tune, self-regulating duty-cycle, Charge-and-hold-logic... THAT is complicated i assure you! ;)

Price? Sure it is more expensive to go with a real Boost converter instead of a bit more intelligent resistor like L7805CV...
Farnell lists an L7805CV with $0.68 and a LT1305 with $3.65
So yes: about 5 times more expensive... And additional costs for the Resistors, Coils and diode... But thats where you have to decide:
A: Shall it be a simple project, having more then 6V at hand is OK and efficiency is not important --> Go with the 7805. It will work.
B: If you want to dig deeper in electronics and want to have the options of going from 1.5V to 12V as input and coming out with a iPhone-capable highly efficient charger which accepts almost every voltage source (Solar, peltier, semi-dead batteries, lead and alkaline, handcrank ...) you can go with one opf the MANY DC/DC-converters out there. If you take a monolythic one (Switch inside) you dont have to do much math for the switching-part...
But be sure: a bit math is included to set the proper output-voltage.

As i said:
The instructable here WORKS. It has some limitations you have to be avare of so you arent disapointed if you want to charge a iPhone on 2 alkaline-batteries with the 7805: It is a double-No-Go with the 7805-solution posted here.
But if you have 6V and more, add a pair of resistors to it, you are ready to roll with the thing even for iPones! :)
I came across a very nice already built switching circuit from a Chinese supplier for $1.70US to charge a Li-ion battery with up to 1A (free shipping, at least to the USA) This could use down to 4.5 volts and was much more efficient than the LM317 circuit I had designed to do the same thing from a 6V source.

So I looked for a USB supply and found a circuit with input: 0.9 - 5V, output: 5V 500-600mA for $2.80US:


It's not worth designing & building one from scratch! This could work from two to four "dead" AA batteries! Well, at least for awhile :)
DanielNorling4 months ago
I really like the project. Good stuff.
But why no curcuit schematic? Written in two languages in nine steps. One schematic is probably enough for anyone that actually can get this done. A good description doesn't hurt, and you wrote a good one.


I have a 3.6 rechargeable batt and solar pannel that makes 4.5-5v will it work
can I make my own rectifier ? Thanks in advance :)

kunala1 year ago

Hey thanks @noise maker for putting this up. i made it and it is perfect.

though i was wondering what is the use of .01 micro farad capacitor?

please revert anyone who knows :)

Awesome! If u selling this or know similar products for sale. I would like to order 20 pieces!

Manu (at)alt108.com

deejayq1 year ago

do you think that with something like this could work better?


i guess it should work. i'm thinking of building a cellphone charger based on this kind of step-down converter, but i need to figure out the values of resistors for D+ and D- pins from the usb plug.

optimus one, the best cellphone ever!

Jkohn191 year ago


jjsims1 year ago
wow! amazing
I made one of those and I'm only 10
Jimmeh301 year ago
I notice there is a little bit of miss information about this circuit's MAX voltage.

According to the data sheet ( http://www.fairchildsemi.com/ds/LM/LM7805.pdf ) maximum voltage input for a 5v regulator is 35V DC. This means an ABSOLUTE maximum of 36.4V DC because of the voltage drop of the full wave rectifier.

For AC voltages (without all the maths) after full wave rectification is approximately 1.44 * the RMS AC VOLTAGE ie: a little over 24V AC

Go any further and you'll see the magic smoke.

Also, as has been stated repeatedly but cannot be emphasized enough, PLUGGING THIS INTO 110V or 220/240V AC WILL ONLY RESULT IN A LARGE BANG, FLYING PIECES OF BURNT PAPER, MOLTEN PLASTIC, MOLTEN SILICON, A POSSILBE FATALITY AND IS A REALLY REALLY REALLY BAD IDEA (as is the design of the casing in this ible)
can it support 220v AC?
Noise Maker (author)  psycotrompus1 year ago
no, max. 30V!
Max 30V DC that is.
i didn't get why did you add a bridge rectifier when you are already getting a dc voltage from the battery
I think the use of what was a mains device is asking for trouble. There is a rule in engineering: 'If it can happen, it will happen'. So, as sure as pigs are pigs, someone will plug this into a mains socket, perhaps without thinking. If the metal tips and wires have been left on, then who knows what will happen. I am fairly sure that the comment in the instructions that it can be used on AC will tempt someone to connect the rectifier input directly to mains supply. Electrical project boxes are cheap enough, surely?
JayGeeBSE1 year ago
To the person who thought it got a bit warm charging at 1A from a 12V supply - do the maths. 12V supply dropped to 5V means 7V across the regulator. 1A x 7V = 7 watts. About half a small soldering iron. No surprise it gets hot. Anyone considering using up to 30V should consider that the dissipation will get ridiculous.

And as for those mentioning mains, don't even think of it. The unit has exposed non-earthed metal parts and is not remotely safe conected to mains, even if it wasn't going to cook.
yes, 7 watts is quite a bit of dissipated heat. the reason i didnt plug the roku into the van's inverter is because every time the vehicle starts, the roku has to reboot. i just had a small 12v battery plugged into the cig lighter and the regulator on it. this way the battery would hold up the regulator as the vehicle starts.
ferjanyen1 year ago
Nice instructable but a circuit diagram would be very helpfull.
from http://www.candrian.gr/index.php/category/microcontrollers/avr/switch-timer/
The values of the caps may not be the same as posted by the OP.
ak088201 year ago
What is the difference between this and a charging adapter for an automobile? Would it be possible to equip that with the alligator clips?
Charging-adapters in cars normally are converters. This one is a regulator.
A regulator drops voltage and converts the overflow into heat. A converter converts the voltage to what you need and wastes only a fraction of the energy.
PhilKE3FL1 year ago
I don't have a iPhone but I had an iPod that required the same voltage on the data-pins. This is in the USB standard, it is the method used to indicate that the charger can supply high current, ~1A. The simplest way I found to "fool" the iPod into accepting the charger as a high-power charger source was to simply tie the two data-pins together. I guess the iPod supplied the needed voltage to itself.
capetry1 year ago
How about putting a light bulb in series with the charger to be able to plug it on 220V!
mihaiachim1 year ago
Not very clear for me if this system work with ~220V or just up to ~30V and continuous voltage?
I think is not working with ~220V can you confirm this?
This is not going to work on mains voltage. Stick to 30V as the limit.

If you have access to 110/220VAC, it is also likely you have access to a standard USB charger.
I am fairly certain it is only up to 30v. You may get away with a little more because it is rectified ac but I wouldn't give it anything over 50. Assuming the ac frequency is 60 hz you get 60 pulses of actual 220v every second. the majority of the time it is actually below that point. I would add a switch with another circuit which either has a 25v voltage limiter, or an ac transformer which then feeds into the circuit in this instructable.
buteman jj.inc1 year ago
Sorry, but because of the 220 microfarad capacitor, the input voltage to the voltage regulator will rise to near to the RMS voltage of the A.C supply so on 220 volts it will be around 220 volts.The regulator will fail and this might be in such a way that your phone could be damaged.
It might not be encountered often, but it should be noted that the maximum input voltage for the L7805CV is 35V.

0805 surface mount capacitors will fit perfectly on the pins of the L7805.
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