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.