A standard Motorola USB charger puts ~1.4vdc onto the x pin of the mini USB plug.
A 200k resistor between pin 2 and 4 produces ~1.9vdc on the x pin. This works form my Motorola Q (which works from ~1.2vdc to ~1.9vdc), but not for my Razr V3m. I had to lower the resistor to 165k. This produces ~1.5vdc and allows the charger to become authorized.