How to Charge Phone Battery with Just a USB Cable

One night, I connected the wall charger to my phone and went to bed. In the morning, I found out that the wall charger had burned out and the phone was no longer working due to no battery charge. The phone would no longer charge even when connected to the PC via a USB data cable. Apparently, the wall charger had malfunctioned and took out the phone’s internal battery charging circuit along with it. Before I could get another phone, I had to work with the same phone and charge its battery. Fortunately, it is very easy to charge the phone battery directly through a spare USB cable.

Here is how you can use just a plain USB cable to charge the phone battery in emergency situations:

  1. Find a spare USB cable that you can work with. If you have any old or dead USB mouse or keyboard, then you can use their USB cable.
  2. Strip off one end of the USB cable to reveal four wires. These wires would be color coded and out of the four wires, you need only the red and black wires. In some cheaper USB cables, instead of the red and black, they could be colored as pink and blue.Charge Battery with USB Cable
  3. Strip tiny bit of these red and black wires. Touch the copper end of the stripped red wire on the positive terminal of the battery. Similarly, touch the stripped copper end of the black wire on the negative terminal of the battery. Use a tape to fix them on the terminal carefully.Charge Battery with USB Cable
  4. Connect the other end of the USB cable to your PC. Wait for the battery to be charged for about 15-20 minutes then remove the cable.
  5. Connect the battery to your phone and it should work.

Note that this should used only in the cases of emergency when no other method is working and you have to use the phone quickly. The USB cable provides the voltage a little higher than the battery’s rating and can damage it if you charge the battery for more than 15-20 minutes.


  1. What if i am using this method to charge batteries that i lost its connector wire. Like i am charging battery from a usb cable connector to the proper charger adaptor. I think everything is same except i am skipping charging through that device circuit.

  2. What if you add a small resistor to the usb cable, would that help?
    Also how long were you able to use your phone for using only the 20 minute charge?

    1. It was a small phone, the battery charged to 10% in 15 minutes and worked good for next 40 minutes. Do not use this method except in very critical emergency.

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