AFAIK it doesn't charge at all through the usb, only through the dc jack.
Edit: Stole this from keyboardmag
PROS:
Both models set a new standard in audio fidelity for mobile recorders, with outstanding dynamic range, detail, and headroom in 1-bit DSD mode. AudioGate software makes converting file formats dead simple. Stereo mic included with MR-1 sounds surprisingly clear and full-range.
CONS:
MR-1 won’t charge over USB, and internal battery is not user-replaceable.
- DSD:
Direct Stream Digital refers to the way in which 1-bit recording represents audio, which is with a continuous stream of ones and zeros (bits) that aren’t divided into 16- or 24-bit chunks.
-PCM:
Pulse Code Modulation, the prevailing method of turning audio into numbers. It’s used in everything from the cheapest CD players to high-end digital audio workstations and dedicated analog-to-digital converters.