Wierd, my battery was so bad on Fc07 i decided to try switching modems. Went back to EL29 and the battery life improved and my wifi signal is flying. 3G is slow but 4G is fast. Don't understand how changing modems would improve battery life and wifi. Could the phone looking for a signal be killing the battery that much?
Your phone will boost the gain for the 3G antenna to get a stronger signal. So yes, a weak 3G signal will drain the battery faster. I don't know for sure if 4G will drain fast with a weak signal or if its just a slower connection.