A question put forth in the "trapped on a boat" thread got me wondering. A person ask if a device could be made the could run any cell phone from any battery. In our BOBs I have these emergency cell phone chargers. They are just an aluminum tube which holds a AA battery and the female port to a 12-volt car powerplug. If you have a 12-volt adapter for the cell phone you can use this to charge/power any cell phone.

This leads me to think that if most/all cell phones can be powered by an AA battery then they should all have very similar power requirements. The reason the have different batteries is to meet the shape-requirements of the phone, not the power requirements.

This then suggests that all cell phone batteries put out similar amounts of power which leads me to think all you actually need for a "Universal Cell Phone Power Adapter" is two peices of wire and some electrician's tape. Just run wire from the proper electrodes of the battery to the contacts in the phone.

Can any electrical experts confirm/deny this. If it's actually the case I need to add a few more things to my Altoids kit.

-Blast

The amount of voltage a device requires is typically dependant on it's battery. Different types of batteries put out different voltages and the devices powered by them are typically designed to operate on that voltage to prevent wastage.

In the case of most cell phones that use lithium Ion or Lithium polymer batteries, the voltage is typically 3.6V but can vary depending on the number of cells and how they're arranged (my notebook has a lithium ion battery but it runs at 14.4V)...this is no different than your car battery. Each cell generates 6V and within the battery there are several cells arranged to product 12V.

In the case of the universal chargers, they work in a couple of different ways. There are the types that are specific to certain types of phones and put out a voltage which the phone will accept. The perfect example of this are the Energizer chargers (the type I'm the most familiar with).

These devices are quite simple and use an integrated circuit known as a DC-DC Charge Pump converter or a Boost Converter. I could ramble all day about how these little buggers work but the bottom line is that low voltage goes in, higher voltage comes out, and heat is generated as byproduct and wastage. This is how a single 1.5V AA battery can charge a device which requires 5V (like an Ipod, or a Motorola or Blackberry phone). You can get these chips in varying input and output ratings but they're not super efficient, relegating them to temporary/emergency uses...or in applications where efficiency isn't important.

You can even make them yourself. There has been a DIY following behind these for a long time. Personally I'm lazy so I just modify the energizer ones to charge anything and everything I own which will charge off of 5V buy installing a female USB port and then buying or making USB charge cables for all my gadgets.

The following is a link to a very talented DIYer who created one of the first home brew chargers and sells kits to build your own in an Altoids Tin: http://www.ladyada.net/make/mintyboost/

Hi Blast,

Most cell phones can be powered from a single AA cell. The problem is that most phones require a 5-6 Volts input. This requires a switching voltage to voltage regulator, which takes the 1.2-1.5 volts of the AA cell and outputs 5 or 6 Volts.

The cell phone will then have a switching voltage to voltage regulator to convert the 5 or 6 volts down to 3.3 or 3.7 volts to power the phone and/or to recharge the Lithium ion cell in the phone.

What would be possible would be to just duct tape 4 AA cells together (gives 4.8 to 6 volts depending on the cell chemistry) end to end together with the two pieces of wire and then ensuring that the wire touches the correct power terminals on the phone. If your phone has a USB type power/data connector this would be more of a challenge.

"... if a device could be made the could run any cell phone from any battery ..."

The answer, broadly speaking, is yes.

Pardon me while I ramble -- this is a topic of great interest to me.

All the phones I've had run on a 3.6 VDC lithium ion or NiMH battery pack.

If you take apart a standard car charger, you will find it's an incredibly simple circuit: it just puts a fuse and a resistor in series, which drop the voltage down to the appropriate level. Mine (for older Nokias) drop 14-ish volts down to about 4.5 volts.

The phone has internal electronics to manage the charge and battery (and optimize its lifespan, etc.).

If you put two AAs in series, to generate 3.1 volts (or 3-AA for 4.5 volts), and had a compatible tip, you should be able to run the phone in an emergency, and put a partial charge on the battery as well. (I'm pretty sure you could improvise a tip with a bit of wire, a bit of foil, some tape, and the tube from the refill of a Bic pen). But: you MUST get the polarity right (normally the centre pin is positive) or risk fatal damage to the phone and/or phone battery.

I'm pretty sure you could attach the same setup directly to the battery pack in an emergency, though this may untimately shorten the lifespan of the rechargeable battery. I have successfully charged them "raw" from a solar panel. But this kind of unregulated charge is tricky -- one went "pop" on me because I left it charging too long.

Other batteries may also be useful energy sources -- such as the 3.6V lithium ions in PDAs, laptops, portable DVD players, etc.

I think the "single AA" chargers must use a "puck" -- that is, a voltage doubler. This is the same kind of circuitry used in LED flashlights that run a LED on two 1.5V alkalines (the LED needs perhaps 3.6 - 4.0 V to run).

I a genuine emergency, where the phone is dead and you have nothing to lose, consider this: if I understand correctly, a phone that's off and close to dead still "pings" local towers, and that can be used to help locate you. You may or may not want to jeopardize that feature by messing with the phone. But if you're sure you have reception, and a few calls will get you out in a hurry, that may be an acceptable risk.

Personally, I wouldn't hesistate to do this. BUT: BIG DISCLAIMER: don't try this unless you accept the risk of damaging the phone and/or battery, and voiding your warranty.

Hope this dog's breakfast of ideas is useful.

If you're going to improvise something like this using bare wires get to know your hardware. Can your phone handle 6v? Is 4.8V enough? I'd rather have a phone with a dead battery than a battery with a dead phone.


Also don't forget that some phones require more complex hookups than just connecting the red and black wires. Motorola phones for example (new ones) use a USB plug but you have to short out certain pins inside the connector or the phone will ignore the power you're feeding it.

Couldn't agree with you more. But the easiest solution is to either carry a spare cell phone battery around with you or one of the commercially made AA adapters or just get into the habit of charging your phone every night. Chances are in an emergency your not going to know which pins on the phone to touch with the wires without knowing your hardware unless you've have a pin diagram drawn on a piece of paper inside the battery compartment of the phone

To get an idea of the voltage the phone requires, it will say on the phone charger supplied with the phone.

That's wise advice: get to know your phone! Open the back beforehand, note the battery voltage (usually printed on it), see if the terminals are clearly marked "+" and "-" etc.

If charging the battery directly (i.e., remove it from the phone and tape wires to the +/-, touch it while charging. If it's uncomfortably warm to the touch, there is too much voltage being applied. Disconnect immediately. Once it cools down, you may still be able to charge in five or ten second bursts, but be aware that the battery is in danger of damage.

Aside: I should add some small alligator clips to my kits. Wire is easy to find; clips are hard.

I bought one of those AA battery charger gizmos for our cell phone (Samsung). It came with 'bout a half dozen adapters, none of which fit our phone. I contacted the vender (bought on ebay), they sent a few more adapters, none of which fit. I decided to keep the thing, gonna get a new cell one of these days, maybe I will get lucky this time. I don't have the knowledge (or guts) to start sticking wires into the slot on the bottom of the cell...

More like does this gal know us or what

Hi OldBaldGuy

Sometimes only a Powermonkey will do.

Thanks. But for $60 I can buy a couple of extra batteries, and use my car charger...

Hi Hacksaw,

For a home brew 1AA cell USB charger would the National Semiconductor LM2623 be a good place to start.

Ladyada uses a MAX756-CPA but it's all the same really. I'd use whatever the local electronics place had if I were to build one.

I just thought of another reason to buy instead of build (unfortunately):

The Mintyboost (and items like it) is an improvised electronics device and if you try to take it onto a plane you're likely to have a very bad day...if they find it that is.

Look at the igo.

link

I've got that Turbo Charge thing, which NightHiker has mentioned a while ago (thanks!), very cheap on eBay with a bunch of connectors for all of my 3 cell-phones. I believe, that the primary problem is actually the phone plug (I have exactly that weird USB powered Motorola phone, mentioned above, and two different Samsungs). It's not always easy to improvise a reliable connector, especially in the field.

Here is my solution. I have all of my chargers wires cut near the phone/PDA/MP3/Radio/GPS/PSP/Camera/etc connector and rejoined back with widely available 3.5mm audio connector male/female pair (kinda bulky, thinking of switching to 2.5mm as on the Turbo Charge thing). Most of these devices needs 5V of charging voltage, so, I'm carrying the single 110V/5V wall adapter, 12V/5V regulated car adapter (regulated means that you can get a stable 5V output from any 9-24V DC input, not possible with a single resistor solution, mentioned above), and the PowerBank thing (which is basically a compact 3600mAh rechargeable battery with regulated (1.5V-12V, 0.5V step) output and 12-24V charging circuit). - Everything with the matching 3.5mm audio plug. Plus, some weird USB/3.5mm charging wireloom cable pair compatible with everything on the picture (just some job specifics ). I'm also have a couple of Y audio splitters allowing to charge 2-3 gadgets simultaneously.

Only some of the connectors are shown on the image (others are in the car at the moment). The bare wires plug is also included (small coil on the bottom left). I'm usually charging the PowerBank first (with solar power in the field) and then, everything else:

Dang, I LOVE THIS GROUP!

-Blast

I have a couple of those turbo charger things. And like any diligent ETSer, I tried it out in a controlled situation. CR@P! It gives you enough juice for a couple of short phone calls on one AA. It seems the newer the phone, the worse it works.

Now the Motorola mini USB charger is fantastic. One fully charged recharger will give at least 2-3 FULL recharges to your phone. I have tried it on three different phones, including my Blackberry Pearl, my wife's Motorola Sliver, and her friend's something else phone. All on one camping trip! I think full recharge of the phone takes 1-3 hours. I am not sure as I charge mine after a couple of days when I am sleeping. My wife's friend's phone went from about dead to fully charged in 1-3 hours. I wasn't really keeping track of the charging time while at camp. But she did use her phone with the charger plugged in. It looked kinda funny, but it worked.

Umm, not quite. The previous poster was right when he said it was a DC-DC converter. Basically this is a step-down switching power supply which converts 12V from your car (or 24V from your truck) to 5V for your phone. It's a small IC-based circuit, a little more complicated than a fuse and a resistor. Most phones, as you say, have a 3.6V battery, and a 5V supply is ideal to charge it.



True. The puck is a step-up DC-DC converter. They convert the 1.5V of the AA cell to about 5V to charge the phone. It won't fully charge the phone, but it will allow you to use it, and AAs are (usually) plentiful.



Sorry, not correct. When your phone is off, it's off. The only thing that is still running is the clock, which is used to activate an alarm clock if it is set.


My general solution is to buy a USB power cable for my phone. I used to have a Nokia 8210, and I had a couple of USB power cables lying around. If I didn't have my car charger or wall charger I could still plug the phone into a USB port on a PC or laptop and charge it up that way. I just got a Samsung phone, and as well as a wall charger it comes with a USB cable for getting data onto the phone which also happens to charge the phone. I strongly suggest that you get a cable like this as USB connectors are popping up all over the place (please keep reading).

I am migrating towards two connector types for my DC power requirements. Anderson PowerPoles for 12Vdc, and USB for 5V. Once you have built a couple of looms and adaptors with these connectors then it all starts getting fun.

Now, you can get wall adapters that run from 110-240Vac and provide 5Vdc on a USB outlet, and car adaptors that take 12-24Vdc and provide 5Vdc on a USB outlet...

and this:

The Boxwave VersaCharger Pro

I found it when I was looking for this:
FreePlay Weza

Which I sort of covet. If only it had PowerPoles instead of a cigarette lighter socket.

A

Oooh, and check out the PowerMonkey too!

http://www.ccrane.com/more-categories/batteries-chargers/powermonkey.aspx

Not forgetting the Powermonkey Explorer of course. (Ruggedised version with solar charger and charge indicator display)

Thanks for the inspirational links! But all those things are huge! My personal goal is to fit all of my power making stuff in EDC kit (on-body EDC!). So the primary criteria for me is how thick it is. Anything more than 3/4 inch (2cm) thick - is not acceptable!

38mm thick solar panel (Explorer)??? Mine is 6 times larger in square inches but only 3mm thick folded with the same footprint!

The explorer solar panel is a dissapointment compared to other folding weather proofed panels such as the panel made by Sunlinq or even your own panel. The Explorer solar panel certainly looks rubust enough though. What I do like is the actual Powermonkey Explorer itself. The charge display panel is a great idea. What I would look for is a 12V to 5V high effieciency convertor to link a Sunlinq panel to the Powermonkey Explorer. The Powermonkey Explorer device is actually not that bulky or heavy in comparision to other similar sized universal Lithium Ion batteries although the form factor is probably dictated by the cylindical Li-ion cell at its heart. I do find it strange that they don't appear to have an adapter to power the Powermonkey from a 12 car cigarette adapter though.

Its the wide range of Monkeynuts and international mains power adapters which make this a useful device. Monkeynuts can be purchased separately to increase the range of devices which can be supported.

From this discussion, it seems that any source of 5-volt power could be used to recharge the average cell phone battery as long as you knew which contact was which... Three 1.5 volt batteries, a solarcell array, a bunch of lemons, copper pennies and zinc washers...

Now I'm picturing some little LED+variable resistor device that will light and indicate polarities up when you are feeding it 5 volts from some jury-rigged system.

My boss really needs to give me more work.:)

-Blast

You can buy very simple three terminal regulators. LM340-5, 7805, etc. Those are available at radio shack but they require a 2v overhead. You can buy low drop out versions from places such as digikey or mouser which only need a 1v overhead. then you can buy fancy switching regulators that will take a wide range of input + and - the output. Very easy to rig up a power supply with some of these.
Our current phones will charge from USB so I'm somewhat standardized there, could pick up any old computer system board or power supply and get a charge from it.

Umm, what?

-Blast (chemist not electrician)

Hi Blast,

Recharging the cell phone battery directly is not really recommended (i.e removing the cell phone battery and attempting to charge it directly) especially if its lithium ion (could catch fire, better to have a dead cell phone rather than serious burns to the hands). Its better to recharge the cell phone battery using the cell phones internal charging regulator circuitry. This is because the cell phone regulator has the ability to accept a voltage variation. If the specs of the phone specify say 5 volts then it is not unreasonable to allow 10-20% variation i.e 4.5 volts to 5.5 volts (3 Alkalines or 4 NiMh AA cells). Of course this requires knowing something about the phones voltage regulation circuitry and which pins are required to be touched by the red (5V) and black wires (GND). Get it wrong and you could have a dead phone. Getting the appropriate Monkeynut for your phone type will go a long way to not damaging your cell phone.

The 3 terminal regulators such as the 7805 are packaged just like a transistor but it is a fully integrated transistor circuit called a voltage/power regulator. Simply put, if you put 9V on the input electrical terminal you get 5 V on the output terminal. If you put 8V on the input terminal you get 5V on the output terminal. So if you have a variable voltage which varies up and down say from 7V to 12 V you will get a regulated steady 5 V on the output terminal. With a 2V overhead i.e 5V + 2V, the minimum voltage the input termanal will accept to work to provide 5V on the output terminal will be 7V.

One of the simplest voltage regulators is a zener diode.

Thats OK, I'm not an electrician either but I have done some house wiring (a lot of people confuse electrical with electronic, an electrician is the guy that wires your house, he doesn't mess with electronic things).

Those numbers I listed are simple electronic parts which are voltage regulators. You simply connect one pin to ground, one to power in and the other to power out. So you can put in a wide range of input power usually 6 or 7 to 15v and get 5v out. If your going to be trying to feed power into a phone then you should look into voltage regulation so the phone remains a communication device and not a fire starter.

Go to electroids.com or adafruit.com and buy a kit for a USB-based iPod charger, and get a USB recharge cable for your phone. That will take care of regulation and let you get just the parts you need rather than having to buy five or ten or twenty of something you need one or two of.

PM us if you get stuck, a lot of us know the electronics, but these are actually a pretty easy kits. You don't have to know what the individual parts do, just which way they go. Don't solder your fingers. Use good solder. Tin your iron, don't count on it being done right at the factory, and remember to get a solder sucker.

I just stumbled onto this thing, don't know if it works or not...

Carport charger

Looks kinda bulky. And advertised as a rocket science acheivement Same 8 AA holders are a buck for a bucket on eBay ( example ). Just add a car lighter socket and wrap in ductape.