Although not recommended and as a last resort only, it's possible to charge the battery directly (after removing it from the iPhone) by carefully positioning the exposed black and red wires from a USB cable on the battery connector. I've done this twice with the non-severed end of the USB cable connected to my laptop (only connect it to the laptop AFTER having placed the wires on the battery). This was quite fiddly to accomplish and I had to tape the wires to the tabletop for stability. I used this YouTube video to pinpoint where to place the wires: https://youtu.be/msamRT284pY?t=17 I left it for about 15 minutes and after putting it back in the phone had a 10% charge. I was then able to plug my phone in and continue charging the normal way. If you attempt this, be careful and know the strength of the power source you're going to plug it into. Also, don't leave it too long.