I'm working on a GPS Arduino Project, I'm using a Venus GPS modual and a software serial connection to get the data from it. I have a battery backup 3.7v (3000mAh) on the GPS that is to keep the GPS warm while the project is powered off. However, the uno ON LED filckers on and off when the TX on the venus is sending data. This is keeping the uno 'awake' and when the power resumes to the project the program will not run untill it's reset.
I think i've just sorted it. By default there is a solder jumber on the venus board next to the V-Batt pin. This links the Vbatt to the VCC. so you can start the GPS by only applying power to the VCC. upon removing the jumper it works as I expected it to.