Ok you all may or may not remember my Nextel phone cable hack posts, Here and Here, but I have one more up my sleeve, "The USB Serial Cable" now you all might say what the heck how can it be USB and Serial at the same time. Well Click on the more link to find out how. It uses this cool chip from FTDI Chip.

I find myself wondering why when I use the serial cable on my Nextel phone for long trips why the battery dies so quickly. Well after some investigation and some previous knowledge I know why.

Well it starts with the fact that the GPS receiver is actively looking for and receiving signals. The next fact that I found through some investigation, soldering wires, and buzzing out circuit boards, was that the phone is not only powering its internal workings but also the external circuitry for the RS232 Driver Chip. Even though there seems to be circuitry in place to shut down the chip when it is not in use. It never is not in use when the phone is in NMEA Output mode. Well both of these add up to some major power draw for the phone battery.

Schematic for Nextel Cable Mod