A special circuit or software is required to force a Motorola phone into charge mode (at least for the model I own). I decided to use the cord from a Motorola charger I got at Goodwill to easily solve that problem. I already had a spare charger that I use in a different part of the house, but the one at Goodwill was only 99 cents, so I picked it up anyway to hack up for this project. If you don't already have one or can't find one at a thrift store, the link here has them for 79 cents (+ a few bucks shipping). These things are everywhere, though. You should be able to get your hands on one if you don't already have an extra one lying around in your closet. But I digress. . . Anyway, the proprietary 'Moto' wall charger has the circuit built into the mini USB plug and therefore solves the problem of getting your phone to actually charge. Here and here are pages including more info about USB pinouts for motorola chargers if you want to make your own.
Disclaimer: I know that you can simply buy an adapter for your Energi To Go unit to power another device, but the ones I've found are $2.99 apiece plus shipping. Also, I like to build my own stuff if I can. If you don't understand this concept you are on the wrong website. ; )
Disclaimer 2: I am also aware of the Minty Boost and am a big fan. If I were really cool I would have made one, but this unit was cheap and here right now--two very powerful aspects in my decision-making process. And besides, this Instructable ties in with another I will be posting soon that uses this same cord. So if you are cooler than me (likely), and you have constructed a Minty Boost, simply substitute the Energi To Go adapter for a standard USB male type A connector instead. And if you bought a Minty Boost, you got nothing on me, so shut it. :p
Okay, I'm done disclaiming. No need for that "don't try this at home" crap.