My 3G BlackBerry Bold on average will lose it’s charge about twice as fast as my EDGE only (aka 2G) BlackBerry 8900. Part of the reason for this discrepancy in battery life is that during periods of poor signal quality the 3G device is constantly looking for better 3G coverage. All that searching takes more processing time and battery power. Someone on the CrackBerry forums noticed that the latest BlackBerry Bold OS 4.6.0.282 which is downloadable via a link to Hong Kong phone provider CSL Limited which enables the option to turn off 3G in your AT&T BlackBerry Bold. This helps anyone who may be in a fringe 3G area avoid having their Bold constantly draining the battery while searching for a better signal. Prior to this update (which while not an official AT&T provided update will still work in the AT&T device) there was no way to turn off the 3G radio in favor of full time 2G EDGE).

CrackBerry and Step by Step instructions to upgrade your BlackBerry OS