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Modifying Android Phone To Run Without a Battery

Abstract

I had few use cases where I needed an constantly on Android phone. The issue with keeping any device constantly charging is that their battery will suffer. In case of lithium-ion batteries they have a proclivity to inflate and even catch fire or even explode. So keeping your mobile phone charging all the time is a big no no.

Luckily there is a way to solve that issue by ripping out the battery and adding an external power source instead of the battery, but even this may not be so easy since more and more entry level phones have a built in an hard to replace battery, so you really have to find a right phone. I tried this mod on several phones LG (with removable battery), Samsung (With removable battery), Nexus 6 (with embedded battery).

The results were:

  • LG (with removable battery): boots up and works for few minutes after that magic battery DRM kicks in and shuts down the phone. So don’t bother with LG phones
  • Nexus 6 (with embedded battery): Fried that sucker. The power pins were super small so don’t bother also.
  • Samsung (with removable battery): Worked like a charm I actually managed to hack 2 different models of Samsung phones both with a removable battery:

So this post will cover my journey of hacking a Samsung XCover 4 to run w/out a battery.

Guide

Schematics

The schematics is relatively simple. I used a 5V, 2A AC/DC power adapter. You may say ask why I did not reuse the original charger? Well the original charger had 2 issues:

  • The output voltage was rated 5.2 V
  • Also the output current was only 1 A.

If the phone will get some heavy load e.g. a video game it may start shutting down or the battery level may drop below a 100% and we don’t want that let’s just tell the phone the battery is at 100% all the time. The battery % may fall because the chargers voltage begins to fall sharply if high current is required by the device that’s why I chose to buy a 5 V, 2 A adapter and not use the original charger.

Now you may ask but won’t 5V directly to the battery pins damage the phone? Since li-ion batteries are usually rated @3.7 V, yes 5V directly may damage the phone’s electronics inside so I dropped the voltage using a single component since I wanted for the circuit to be as simple as possible. I just used a high current FUF5408 diode. You should keep in mind that diodes don’t drop voltage at a fixed point diodes also have

here is the original schematics (not very clean I know!)

schematics

R_1 = 12k Ω, 0.25 W Resistor
D_1 = FUF5408, High Power Diode

[NFC] -- Not used
[-] -- Negative (-) power rail duh
[S] -- Thermal resistor pin, originaly thermal resistor is built into the battery.
[+] -- (+) 🙄

here is how the module looks like when soldered

sk-module

As you can see module uses 4 pins well actually only 3 of them since the left most pin is used for NFC data. Yes Samsung batteries have NFC antennas glued on the batteries and not build it to the phone! Since I did not really need the NFC I did not bother connecting it. Also as mentioned before thermal resistors are also a part of the battery, that’s why we used 12k Ω resistor, because we need to fool the phone into believing that battery temperature is OK.

sk-module2

module back

For the soldered module I used simple breakout board. Fun fact Samsung battery pins are spaced in the good old INLINE manner meaning that the distance between the centers of adjacent pins is equal to 1"/10 = 2.54 mm

module-wire

If you are attentive enough you probably noticed that the top part of breakout holes are cut in half having a U shape and not plain O hole shape. This was intentional, because I wrapped the contact pins w/ one striped wire from the CAT-5 cable.

product

And here is how finished hack looks like. I simply used hot-glue to keep the module in place also make sure you hot glue the wires as well so that under tension they don’t transfer any “wobbliness” to the module itself.

Final Thoughts

  • This “no battery” method worked quite well for me and proved not to cause any issues
  • The work and components involved are readily available and easy to put together
  • NFC can be added if needed you simply would need to peel of the NFC tag from the original battery.
  • Phone in this configuration, can be used as a cheap IP camera using IP Webcam app
  • If you are paranoid about the voltage levels of your “no battery” mod you can use the BatteryBot to check some battery stats.
  • I would only bother w/ Samsung phones & only phone w/ removable batteries because from my experience it is guaranteed to work and easiest to mod way.

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