I use the following library: https://github.com/rickkas7/AccelWake/blob/master/accelwake_electron.cpp
But instead of connecting INT1 to D2, I connect it to WKP and enter Deep Sleep. When the device is connected by USB cable, it wakes up fine. When it is powered only by the battery however, it will not wake up anymore. I tested it with several devices and several protoboards, and none of them work.