I'm currently on 5.1, but want to flash 5.3. Has anyone done 5.3 directly over 5.1 with no wipe? I really don't feel like setting it all back up... (feeling rather lazy if you can't tell

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crap i was flashing with rds lite and battery died I didnt know it was low and flash failed
You need to hard-wire your battery to a USB port via a chopped off USB cable, unless a proper external charger is at your disposal. Or a friend with a D3.
To hard-wire it, chop off a USB cable just before the end device (DO NOT use your Moto cable for this, an old mouse cable, camera cable, etc. will do) and then expose the 4 wires. There will be a red and black inside, cut the others an inch or so shorter than these two. Expose 1/2" of each the red and black and fold them over themselves to double the thickness. Remove your battery and insert the red into the + and black into the -. I taped my in place for security to prevent a loose connection.
NOW, you can plug it into the USB port. Connect the battery securely first.
The battery is, IIRC, ~1500mAh and the USB port puts out .5A, so charge it for an absolute MAX of 3 hours. I would do one, then pop it into the phone to finish charging if possible. Just keep an eye on it and make sure it doesn't get overly warm. This is a riskier way to charge since it's directly wired to power, but when you're bricked, it does work.