You open your messenger bag at the coffee shop only to realize your laptop is nearly dead and its power brick is at home on your desk. After all, there are many daily habits that can kill your laptop battery. If you're trying to figure out how to charge a laptop without the charger that came with it in the box, don't worry because modern tech has your back. People often ask if they can charge a laptop with their phone charger. Plugging a low-power cord into your laptop lets it charge slowly if it's powered off.