Good day, I am new here

The project I am doing is connecting my wrt54g to my 4270 roomba via 3.3v serial. I am not to much a hardware guy as much as I am a programmer. But I do enjoy working with the hardware and then programming at low level to interface with it.
The Problem:
My router goes into boot cycle just fine volts are at 15.67 then at the same time every time. the router turns off and then the multimeter displays 2.7v. Anyone have any ideas? I am using pin 1 Vpwr Roomba battery + (unregulated) which is 16v out.
I have tried using pin 1 and 2 together and that did not help.
I have tried hooking the router directly to the battery. And that works, but I cant do that in reality. (just to test if the battery was the problem)
Does anyone have any idea what this is happening?
P.S Please don't just say, "why dont you just go out and buy a pre made wifi adapter" or anything like that. I am doing this because I have random electronics around the house and I had a pretty cool idea to do something with them.
Thanks in advance! I really hope you guys can help me.