Just some information for people who wind up in this situation. Let's say you decided to SBF your phone and it said you had enough battery to start the process. Well as soon as the phone gets the low battery message the SBF will stop. It seems like it will do this no matter where you are in the process as well. Since the battery is sealed, you can't take it out and charge it in a standalone or slap it in another phone to charge.

Here are a couple solutions:

How/why to make your own Motorola "Factory Cable"

Charge Your Battery Without A Special Cable Or Taking The Phone Apart! - RAZR/RAZR MAXX - droidHIVE Forums

I hope no one has to do this, but I did months ago. Someone just said something that reminded me about it so I decided to post.