If you do not live in a 4G LTE area than you will want to go to Wireless & Network in settings and go to the Mobile Networks and in system select it is set as default "LTE/CDMA" select CDMA only and it will stop looking for the LTE network. I did this and my phone went from going dead at 2pm to being at 30% battery when I go to bed at 11pm

Also Juice Defender does this as well?

 

I don't think jd can do network switching (I don't see an option).

 

right, when the screen is off, jd just shuts off the networking and periodically turns it back on so another program can do it's updating... but if a call comes in, it still has connectivity to receive the call.