Take a look at this post, and the entire Thread :
Disable System Power Manager
But as previously mentioned, I haven't found a need to disable System Power Manager when charging through the USB connector.
The Startup Macro is used in the sample code in this current Thread.
It's where I select between Mode 1 (API) or Mode 2 (PMIC).
It's probably best to stick with the New API, especially since the Device OS firmware will likely continue in that direction.