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Topic: Free Power (Read 2095 times) previous topic - next topic


Now that I have your partial attention an Idea came to me... yes at least original to me... I was looking at 3 different Samsung batteries and noticed that the contacts were the same for all three and I thought Gee... really, I could charge all 3 from the same phone... Then I remembered that it is good to 'disconnect' the load when the battery voltage drops to a certain value, Thats easy... But also I need to charge the little buggers, I have several spares and some strays. So inspiration or use your mind for something besides keeping your ears from looking like a really ugly, hairy butterfly and I wondered just how hard it would be to hack a cell phone and use the internals for the charger and bring out the battery power and whatever the shutdown control or just use switched power anywhere inside to control an external switch to kill or disconnect absolutely, one of those cheap boost Switchers one see's on Ebay all over the place... If you can only use 3V3 its a natural... A .96Ah3V7 source and a schottky make 3V3, for a 5V source I bought a boost Vin< Vout adjustable converter for $2.85 US and I think I really got robbed as the parts are the same as the buck mode, just wired differently and the buck mode was $1.89 any way it sounds perfectly do-able and just think a self contained recharging Li-Po 3.7V battery pack with charger just for the cost of a small case and a little wiring @ 3.75 Whr, Thats like 750 mA for an hour... No servo's or motors but a bunch of LEDS... Yeah... and small too. Frequently they can be had for the asking, sometimes you might have to buy a $5.00 or so battery but Still Cheap for that kind of no hassle power source. Pay for itself in a couple of month's of batteries even better for smaller lower current projects, like would be Super easy to make a solar powered data logger for less than the cost of another rechargeable battery of similar capacity and the typical one is lead acid Gel Cells, UUgh, thats good for a year tops regardless of how well it is maintained electronically..   IMO

--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard


wrong title, use something like "hack batteries", because actually there are way to get "free" power, and this is confusing.

IMHO you should NOT hack a battery, specially if from cellphone. normally they are litium or (older one) NIMH. and this is dangerous, they can provoke chemical fire that you can turn off just with some water. Also inside they have just a basic circuit to auto-tun-off the battery if it's internal voltage is critical.

read something about this chemical and this kind of battery before play with them, they are quite dangerous if not handled correctly (never heard about a phone that auto-burn himself?)
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I wondered just how hard it would be to hack a cell phone and use the internals for the charger and bring out the battery power

With access to the schematics, it's dead easy.

Some paragraph breaks next time, maybe please?
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.


I agree about the paragraphs but it is the way I think...
I liked the idea of hacking the cell phone, there are always a ton of them around free. Let the phone manage the power, both ways. An external switch tied to some or any active power internal to the phone would be the control.
I had NO intention of advocating anything else. This idea is for stable projects... Not for cowboy style hacking or creation of monster light or robot things... more in the line of Led's pr LCD's. I had really intended it for more personal items like an nRF24XX series transceiver, a key pad and some kind of control for remote control or monitoring like a perimeter alarm or overflow or... Fire or... the list is virtually endless.
I wonder just how hard it would be to get control of the display??? Or if there is a phone that has an easily hacked display?, keyboard as some of the keyboards are rather fully functioned and free more or less to disconnect and use. There are what are called "pin boards" available from several people on Ebay. There are also "adapter" boards for fine pitch ic's that might serve well for this purpose as well.
It does seem a shame to discard items that have good functionality like the ones I mentioned. I prefer to recycle older things where ever possible... Old or discarded satellite boxes have separate PSU's that are great because they have already been UL approved... more or less and as long as they are treated like a brick and left as integral as possible they make great power supplies, many are very well filtered on both line and output. Capacitors, Chokes, Switches on PCB's... Cut them up and use what you can. Discard what you can't... likely the device was a discard anyway.
As you knew I put the title Free on it to get attention, looks like it worked although the first responder apparently didn't read what I wrote carefully. Thus your admonition to break my thoughts up into digestible bites. Thank you sincerely, typing is difficult enough for me as I am arthritic and some of my fingers don't work as I would like and I suffer from a mild form of ADD. It was really hard sometimes to get good design work done with this condition... It's like every 20 30 minutes or so I loose focus and have to go back and retrace or retrench. I succeed for 20 years on my last job though.

--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard


Hi Doc,

For lithium ion batteries, the nominal cell voltage is 3.6V. However, in practice the cell voltage will vary from 4.2V when fully charged to the usual end point voltage of 2.6V. They have no memory effect, and can be stored either charged or uncharged. However they lose storage capacity from the moment they are made - it used to be about 10% per annum. Many of them have mechanical, chemical and electronic protection built in, and the third terminal generally communicates in some way to the charger and/or the load, to regulate the current/voltage. However, you can make a simple constant voltage charger, set at about 4.1V per cell, and in many cases ignore the third terminal communications. At 4.1V , you will not get the full charge into the battery, of course. More than 4.2V will not work - either the protection built into the battery kicks in, or if none present, it explodes, or worse.

If you want a flat voltage discharge, and a simple charge circuit, Nicads are best, but they have memory, and don't allow them to fully discharge. The simplest charger for a more robust battery is for lead acid gell - Gate's Cells are pretty good, and monitoring the voltage on discharge will give an indication of the remaining charge. NmH cells are tricky to charge fully, and do not have the flat discharge curve (oxymoron?) of the Ni-cads.

The choice of battery technology depends on the type of load you will be using - Li-ion will shut down if you are powering, say, a circuit with large capacitors, or you will need some sort of 'soft start' since it sees the inrush curent as a short circuit. However, a cheap li-ion does not always have the inbuilt protection, so it will either be OK, or most likely it will self destruct, taking part of the local environment with it. :smiley-yell:

Best wishes,



I agree fully on all parts of your reply But I never intended it to be purposed for high current load,s more like a monitor for a gate or something similar... maybe to read an RFID card at a remote gate or entry and transmit the data back to a monitoring station. I DID NOT however consider the "Average" user here when that "Bright" idea came to mind. I Never considered the possible abuse the hacked device might be subject to, Perhaps I should go and kill the original post before some fool blows his pointy little head off... Do I need a resistor for this Back Light?... and much more of the same. Sorry about my answer but I'm not feeling well too hot today and the first real SO Cal Summer day. Sorry about it... NOT!... it has been a good chance to expose people to larger views on portable power, requirements and materials... Still think that a solar cell and a phone would make a great low power re-purpose for a small low traffic power supply. But since I retired I no longer get paid to think... now I do it for free and you know what free is worth...

--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

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