I have a ITEAD 3G shield (https://www.itead.cc/wiki/ITEAD_3G_Shield) that I want to run it off li ion batteries. The sim5316 module requires 3.3V-4.2V voltage to run (perfect for my batteries), but the 3G shield requires 5V. I assume this is to be compatible with the arduino 5V output, but it means I'll have to use a step up voltage converter just to have the 3G shield presumably step down the voltage. Does anyone know how I would go about bypassing the voltage regulator, or even if I can/should?
I suggest using a Step-Up circuit providing a min of 2A. Its available online. You cannot bypas the voltage regulator.
Hope it helps.