18-year-old Eesha Khare of Saratoga, California won the Intel Foundation Young Scientist Award on Friday, at Intel's International Science Fair.

The award comes with $50,000 in prize money . . . and Eesha won it for something she invented because she was sick of her cell phone dying all the time.

She designed and built something called a supercapacitor . . . which is an energy storage device.  Basically, it's a new kind of battery.  Instead of taking hours to fully charge your phone, Eesha's invention can do it in 20 or 30 seconds.

It ALSO lasts 10 times longer than normal cell phone batteries.  And it can be recharged up to 10,000 times . . . compared to 1,000 times like most current rechargeable batteries.