Introduction: Power an Android Phone Without Battery
This idea came to me when I built another project
For my needs, I had to have an Android alaways on but I didn't want to let it pluged on a wall with the battery cell inside. A battery that is 24/7 on charge can be damaged and start a fire ! So I wanted to bring power from a wall plug, directly in the phone.
Be careful ! Here we will play with electricity and battery cell. Those elements can be dangerous if you don't know what you're doing. I can't be responsible of any damage caused on your equipmentor on yourself. So please, read every documentation you can found BEFORE starting anything !
Step 1: What Numbers Said
For this project, I use an "old" Samsung Galaxy S3. Numbers I'll give will just be correct with this model. Please check on your device the values you are looking for.
When I removed the battery cell of my device, I found a little label that said the device should be powerd at 3.8V. I found the same number wrote on the battery cell. But when I looked on the power plug, I saw it dispense 5.0V. We will need to reduce this voltage in order to not damage the device.
We can see on the device four little pins. Two of them are the +/- poles to power the device. To know exacly which one does what, you can look on the battery cell. It should be + and - symbols in front of the right ones.
Step 2: Gathering Parts for Assembly
First of all, we will need cable between the power plug and the device. Took an old USB -> micro-USB and remove the micro-USB head.
If you remove the plastic protection you will see multiple wire. We only need two of them : the red one and the black one.
Here comes the hardest part. In order to make a good contact between our wires and the pins on device we will use a part of the battery cell itself.
With thousand precautions, you can start to remove the plastic sheet protection around the battery cell. You will expose the part we need : the one with four contacts. On my model, this part was protected with a little piece of plastic that I removed with a small pliers. With a small blade, you can detach this little part. See pictures to spot it.
Step 3: Welding Parts
Using all those parts, if I measure output voltage I found 4.83V (don't mind the Arduino, it's not even plugged). It's less than the 5.0 wrote on the battery cell but it is still a bit high and it can damaged the device.
You will have to weld the red and black wires on the little battery cell part. The cell itself can be use as reminder to know where plugged which wire.
After all of that, the output voltage is still a bit high but it will do the thing.
Step 4: Power the Device
Ok, now you just have to put your assembly into your device. For my part, I used a small piece of cardboard to hold our it in front of the four pins.
Hold your breath and... Yay ! The device starts \o/ !
Thanks to the Ampere app, you can control the device input voltage. On mine, it displays 4.2V. It's a bit high but I don't think it will damage my device.
Participated in the
Invention Challenge 2017
3 years ago
My friend suggested another solution to this problem.
He just wired another cell phone battery to pins in the battery compartment, charging it via standard micro usb connector, so no need for Arduino or step-down converter.
So frankly speaking I am looking for an adapter to let me use any 3.7V ion cell battery for any smartphone ( outside or inside mounted).
Let me know your opinion
Reply 12 days ago
Don't know what you are achiving here... the object is to run the phone WITHOUT a battery, you are just running the phone on a random battery but still a battery.
Reply 2 years ago
the battery will die within a year if it`s always plugged in
Reply 3 months ago
My flip-phone was plugged in 24/7 for 8 years and the battery was still usable, though unsurprisingly not as good as new. You'll kill the battery faster by wearing it out through deep discharging and fast charging. The ideal would be if the phone would only charge it 1/2 way to 3.6 volts.
12 days ago on Step 3
What a confusing narrative & picture sequence.
3 months ago
Normal battery voltage for phones from a lithium cell would be between 3 and 4.2 volts, so applying 5 volts is well above normal. The best solution would be an adjustable voltage regulator set to between 3.6 and 4.2 volts. But, if that's impractical, try using rectifiers like the 1N4005 (1N4001 to 1N4007 will work) to drop the voltage. They'll provide a more constant voltage drop than a resistor. Splice them inline with the red lead from the USB, the ends of the rectifier with the ring marking goes towards the phone. That should drop 5V USB to about 3.6 to 3.8 volts.
Tip 4 months ago
SOLUTION... Hi to all, firstly. Not to waste anz more time.
Use resistor with value calculated to achieve desired delivery voltage. At the same time the source must also be capable of at least the current needed by the device plus 5% higher of that value. Higher than needed is not a problem. But lower than nominal is!
As in this case voltage needs to be lowered from 5V to 3.8V. Use a resistor lin linear positive wire and with the value calculated via Ohms law R=U/I. R1=5V/1A=5Ohms. R2=3,8V/1A=3,8Ohms and finally R3=R1-R2=5Ohms-3,8Oms=1,2Ohms (the one you should use here). To be sure... U(V)=R*I=1,2Ohms*1A=1,2V. Which is a drop we need to get 3,8V of 5V source.
HOWEVER! This current is not sufficient for most of the smart phones nowadays.
USE a charger or DC power supply with 2A or higher. THAN RECALCULATE THE VALUE OF A RESISTOR NEEDED.
In any case of source it should match the specified voltage of the device as much as possible, if not rather exactly in any way. Better be sure of that.
WARNING! Do not use a power supply with too high values or to much power. Ussualy a very powerful power supplies eve would not work in this way. Then it needs a different aproach. More safety issues and not intended for such low power loads. Use a max. of 12V and 3A. Or a bit higher if it so happens.
DISCLAIMER: This is a direct instruction for thisws case, this post. In fact there are many facts surrounding this area and to consider. I Included them in to consideration, but did not mention them.
As to the link between the other two pins of the battery connections and the values and dependancies. For one example...
The procedure in this post by itself is technically correct. And the least complicated way to achieve the goal.
This will totally suffice to get what you intended here. As for the procedure itself and instalation of it all, that is for everyone to decide as it fits.
Question 4 months ago on Introduction
Hello there !!! Please, i like to know: could this principle be used to run a nintendo switch without battery ? In the ideal case how exactly ? The question is nagging me because when the end of its lifecycle comes it would be extremely sad. Theres many folks who also would like to know. I would be extremely thankful if i could get an answer from someone who has your know how.
1 year ago
I have an old Nook HD+ tablet the battery of which died. I've tried attaching different batteries but none seem to work. What I did is I cut the wires coming from the dead battery and attached these two (red and black) wires to a different battery with the same specs (3.7 volts) so that on one side the wires are connected to the new battery and on the other side, they are connected to the tablet like they were with the original battery. However, it doesn't work. The latest battery I tried is an Ipad one, and with the Ipad battery alone, the Nook doesn't power on, and when I connect the wall charger and turn it on, the Nook display turns on for half a second and then turns off and then nothing happens.
The method you've outlined above gives the current to the device without using a battery. I've found a small device named "almac combo of 5v 1A Micro Usb input for 3.7v 18650 Lithium Battery Charger With Protection Module, best for robotics DIY kit" which seems to be doing the same thing:
If I connect the red and black wires of the Nook to this Almac device, will it power on the Nook, without a battery and without connecting it to its own wall charger?
1 year ago
This works but after time the phone will still turn off. I guess it times the battery that it thinks it has even though the volts don't go down and it will turn off. I guess need a power supply that goes down some volts and back up like a battery would. Seems like no one got this to work so a phone will stay up for like years on a power suppy.
Question 2 years ago on Step 1
how to reduce voltage !!plz help
Answer 1 year ago
There are ways a little transformer. 2 insulated wires a magnetic field between them to step down the power.
Or can use a transistor to turn the power off and on fast with a capacitor Charge up the static in the capacitor just some till it get's to the right volts.
Answer 2 years ago
you can use a resistor
Question 2 years ago
Hello there, just to be clear, took BMS circuit off the li-on battery and soldered ground and Vcc directly to B+ B- and then just powered on the phone? Regards
Question 3 years ago
Great idea for a spare phone at home that does not need mobility as a feature - that is exactly why I would want to do it. An extra phone running Apps I use watching TV or working at my laptop. I would the run less apps on my primary phone if I could do this!
Has anyone tried it on their Samsung Android ROM version and were there any disadvantages ?
Some reading on the web suggests laptops power switches in parallel (battery/DC power charger) which is why they run just fine without a battery, and the design for MOST smartphone is a series connect (battery+DC power) hence the need to connect something to where the removable battery connectors. Obviously you need a phone model with removable battery (eg older Samsung models). Does what I read sound right?
More reading on "Dr Google" suggested that peek current (Amp spike) may not be sufficient with just a standard usb charger DC supply connected to the battery terminals. I am not sure if this was meaning your typical 5V 500mA charger - most Samsung chargers like one used in this Instructable are 1A is that accurate?
The "peek use", typically at power on, is worth testing with a 500mA charger. For me, that second phone might be plugged into laptop port (=500mA), or I want to plug it in to the closest standard USB charger I have available which is not always the Samsung supplied charger (1A). The usage at home will typically be WIFI connected, and streaming with a Chromecast; or an extra skype voice call; so this is probably low chance of hitting peek (I assume). Would a peek use case be one or all of the following: phone call using mobile network (assuming available); screen casting (mirroring) your screen and then watching stream content (e.g. Youtube); Whatsapp/Skype/(any other VOIP app) video call with phone brightness on full. It would be interesting to know if phone would keep running under these conditions. I am basing these examples on times my phone battery could not cope.
Answer 2 years ago
having done some testing with a nexus 5. I`ve seen it go up to 2A in benchmarks. I`ve got some capacitors in parallel to compensate for big spikes, but a good power supply is still needed.
Question 2 years ago
Need some help with sony xperia z2. I want to connect to power directly but the connections are complicated. Please advise
Answer 2 years ago
measure the pins, see what`s positive and negative. Try if it works. Please don`t plug it straight to 5v tho. Only luck will save it
2 years ago
I added a DC-DC voltage pull down regulator after a 5V 2A wall wart, I did this project on the S3 as well, nice to see them live on. I use it as a baby monitor and have fried 2 batteries as it's always plugged in. Did resuse the battery part as well but soldered it on with some wires instead of the cardboard solution. Then I hotclued it all in the batteri compartment for nice rigidity. Did try a few things but found the obly thing that this setup cannot handle is to use the camera with the flash enabled as 2A is apparently not enough when it goes full brightness!
2 years ago
Hello.. Can anyone tell me how to set the device to turn on automatically when I connect it to the external power source?
(It is a Samsung Note 3 (rooted) and everything went well.. I didn't attach the circuit strip salvaged from the battery.. just connected to a 5V USB port.. No over heating issues by the way.. Now I can turn on the device with external power but manually.. I want it to automatically turn on when I connect it to the external power source.. please help.. 🙏
Another problem.. ☹️ When I turn on the device it shows 100% battery.. (because external power source is higher than 4.4V right?) But after about 30 minutes, the battery percentage starts to decrease gradually.. how can it be?