Let's Make Robots!

why won't my phone charge?



Just kidding. This is scraping the bottom of relevancy though.

Could you perhaps point me to a good documentation source for charging a 3.6 V battery in an old Nokia? Or could you solve my problem directly for me?

My dad is about to go walkabout in the south of Europe. He bought a 12 V photovoltaic power source that folds like a wallet. He seeks my help on the simple stuff, like mechanical compatibility of connectors and pinouts. And soldering.

That's the easy stuff. I managed to hook up V+ and GND correctly to the phone. But it still won't charge. It obviously knows what I am trying to do, but teases me with one liners like "please reconnect the charger". Like that would do any good.

So, unless you already linked me the right pdf or DIY phone community, let's make Nokia charging robots!

I noticed the original charger uses three wires in its cable. Red, Black and Brown. The charger puts out V+ (6.2 V nominal) onto red and brown when not plugged into the phone. Any ideas what the function is for this extra wire?

I am also concerned with the varying output voltage of my source. Depending on light exposure it will produce anywhere between 0 and 15V. It is rated as 12 V and some 433 mA. Would the Nokia protect itself against anything higher than 6.2 V? Is this the reason I am failing here? Should I put in a regulator? Should it be 6.2 V or 3.6 V ?

And first off: would that convince my phone to accept the charge?
And way after that: what about efficiency?

Any help appreciated.

Update: found the model in image search: it's in the 3300 family. Probably a 3310.

Nokia 3310

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So I finally decided that all my previous testing was invalid. I did not have the 3310 with me and the chargers were all designed for 230V AC in. Except for one car charger that was not designed for Nokias. I corrected that todayat the expense of 13 euro. After a brief test in my car, I cracked the charger and found very little room for adding components or connectors.

But then I noticed I had a female connector I could fit in the "nose" if I would remove the shiny pin. Now it connects to one of the many convertor cables that come with the solar panel.



Here is the proof. It works! No need for bright direct sun light. Overcast is fine. Behind a window is fine. Batterij wordt opgeladen! Even if the solar panel outputs about 7-8 Volts, it will start working. Once busy charging you can even take the panel indoors and the charging will continue even if the produced voltage drops under 7 V. I reckon the Nokia charger halts at 6 or 5 V.


Whoopee. Or not? I consider this not a neat hack, but cheating. I don't really care about that. It comes with working to deadlines. Deadlines kill creativity. So stop hurrying me on those legs dammit!!!

I think it's a good hack, I mean it works, don't it?  Shows a quick easy way to get a solar panel charging something that can be a bit finicky.
That's great Rik, the DC-DC converter in the charger should be reasonably efficient. So why didn't you do this in the first place?
No one would/could tell me that
- Nokia car charger are different from the generic ones
- There is a great DC-DC converter in there that would make the solar panel an efficient source

When you get the chance you should measure the voltage developed across the solar panel terminals while the DC-DC converter is operating. I will call this voltage V_sp (solar panel terminal voltage)

If V_sp is close to the rated 12 volts, lets call this V_pmax (maximum power voltage), you're efficiently utilizing the panel. (That rated maximum power voltage is probably at 25deg Celsius - it will decrease with higher temperatures)

If V_sp is less than V_pmax you get a linear decrease in power output from the panel.Not ideal, but certainly not critical either.

On the other hand if the terminal voltage is higher than 12 Volts (V_pmax at room-temperature), power output ("available wattage") will plummet rapidly.

To summarize this short lesson in  practical photovoltaics:
During excellent conditions and proper loading, meaning to keep V_sp at V_pmax (In this case 12 volts), your panel will develop about 5 Watts of power.
Under the same conditions the panel will give you about 2,5W if the terminal voltage, V_sp=6 Volts, and close to 0 Watts (!!) if V_sp=15Volts.

 Then again, none of this may matter much in this application;
Say you measure 13V across the panel - the implication of this (Due to the capacitor at the converter input) is simply that the panel provides more power than required by the charger, and so sorta limits itself.

Or rather it may matter, but "upside down" of what I originally thought it would;
If the terminal voltage is below the rated 12 Volts you should be able to increase efficiency by shutting down the converter until the voltage across the cap reaches V_pmax. Then again why break something that works, or complicate something simple etc.

In the end, if you get the correct voltage at the converter output I wouldn't care about mixing things up.

PS: Out of curiousity I would still love to see some measurements if you can provide them, specifically panel voltage and charger output voltage for a couple of different lighting levels (Point the panel at the sun for one, and aim it about 60degrees off-axis for number two, corresponding to about 1 and 0.5 in relative incidence.)  And remember that these numbers will be mostly irrelevant unless the charger is actually charging something ;)

I don't have the numbers you ask for. And certainly not under load. The panel has returned to the owner (my dad). He will report back to me how practical the solution was. He will use it in Spain in the spring, so I suspect he will never run out of juice. More likely he will wear out the connector in the phone.

I did some crude measurements without load. The panel reached 15 V in full sunlight and refused to go even 0.1 V higher. That would be explained by the physics inside each cell multiplied by the number of cells in series. On a bright day, in the shade of my house, it would still read 12 V. The phone charger only required like 8 V to get started and the produced voltage could drop below 8 V before the phone would stop indicating charge operations. I have no idea how long it will take to recharge a flat battery. My "client" will tell me after he finds out. I don't have the heart to rapidly discharge the battery. I already rendered the battery in my precious 6310i useles by discharging it through a 5W 1 Ohm resistor aka 2 cm pencil lead 8-( .

Generally Li based batteries need to be charged at a set current until a set voltage per cell is achieved  (4.1V for LiPo, 4.2V for some others). You should look at the specifications of the original charger and match them precisely with both voltage and current regulation. A typical Nokia charger puts out 3.7V @ 355mA although this varies with different models and brands.

You need to be very carefull with this. Li based rechargeable batteries are particular about how they are charged. Overcharging them tends to make them explode. The temperature sensor is an important safety feature. These batteries can't be trickle charged and using the wrong voltage is dangerous. The phones have a special circuit for charging their battery but even if you don't damage this from using 12V which is way to high then you may still  damage the battery if the right amount of current isn't supplied.

If you really need to do this then a stepdown DC-DC converter will make the most of your solar power and a current limiter should be used. Considering that's what is in a good car charger anyway I would just buy one and connect it to the solar cell.

That's my two bob worth.

I can't count how many times i dropped my good ol'3310 on the floor... and never broke it! Now phones (including my actual phone) with those big tactile screens are made of sugar!
3 screens ive been through on my n95, there is no protection for the screen at all. 
The 3310 may be old, but its a fine phone. It out performs all the swanky pda type phones that my co-workers get and then compalin that they can't get/hold a signal