Когда прибор теряет связь со спутником, а потом снова находит этот же спутник, то с нормальной батареей он тут же берет данные из оперативки.
А разве оперативка не запитана от основного питания при включенном приборе?
Ну если он дату/время не теряет во время работы то да, запитана. По-другому, я думаю, никак. 
Я это наблюдал лет 4-5 назад, когда прошивка была 4.0
и на всех выпущенных приборах батарейки были почти новые.
Но думаю, если проэксперементировать сейчас, то будет тоже самое. Ибо после замены внутренней батарейки, жалобы на плохой прием исчезают.
А вот что пишет Garmin по этому поводу:
Portable GPS units have the ability to experience loss of satellite reception as a result of Radio Frequency (RF) interference caused by a variety of sources. These sources can be as simple as a portable MP3 Player or cell phone used for in flight entertainment to a ground based air traffic control radar antenna on an airport. When these devices are powered on and are in close proximity to the portable GPS or antenna, the GPS may lose satellite acquisition as a result. Another common source of RF interference is aircraft communication and navigation radios. When certain radios are tuned to a specific frequency there is the potential for enough RF interference to be released that the Portable GPS unit will experience loss of satellite reception as though the signals were being jammed. An article in the Aviation Consumer, dated February 15th, 1994 has outlined a list of aviation communication radios and frequencies that may cause a portable GPS unit to lose satellite reception in the aircraft. This information is listed below.
Radio Frequencies That May Jam GPS Receivers.
• Narco MK 12D/E Com 810/811, Nav 824/825
• Com 131.220 and 119.285 Nav 115.464 and 109.672
• King KX 155/165
• Com 131.820 and 119.885 Nav 116.128 and 109.564
• King KX 170/175
• Com 122.285 and 130.186 Nav 113.651
• Collins Microline
• Com 132.720 and 120.785 Nav 116.028 and 109.464
Notes: KX 155/165 transmitting on 118.15 was shown to jam an external mounted antenna. Narco MK 16 tuned to any 115 or 109 Nav channel was shown to jam a hand held GPS. Narco MK 12D/E and Nav 824/825, if not wired with memory keep alive, will default to 115.5 MHz in the active channel and will jam any GPS receiver.
