as usual, i'm coming at this from a perspective of having had the Forerunner 935 for more than 4 years. when i bought it, it was advertised as having up to 2 weeks smartwatch mode and up to 24 hour of GPS activities.
in the time i had it, i would say the 935 lived up to those specs and then some, even with me using a 3rd party watch face (JBlack) that displays seconds and HR at 1hz. even now at 4 years (still running FW13.00 which probably helps), i still see a roughly 4.5%/hr burn rate for GPS activity (1 sec recording, no GLONASS nor Galileo) and about 6+%/day for smartwatch mode (no notification alerts except for phone call). in the few instances when i was sick and inactive (not using GPS), it would always see a projection of 16 days of battery life in smartwatch mode.
the 945LTE has on paper, better specs than the 935 for battery duration under GPS usage, but i'm finding things to be significantly below spec. i admittedly only have a few hours of GPS measurements under my belt, but in similar settings as my 935, i'm estimating burn rate to be about 4%/hr which is about what i got with my 935 when new. nowhere near the 3%/hr that the 35 hours spec suggestions: . i don't see how i would get close to the 35 hour spec. perhaps, i will need to do a long duration, multi hour activity like a hike during my backpacking trip to get a more accurate numbers because it appears the updated version of the excelled BatteryMonitor widget seems to only round the reported battery percentage. (the old version on my 935 would report, perhaps somewhat inaccurately, the percentage to the nearest tenth)
similarly, the 945LTE, from again limited date, seems to burn through about 9-10% day in smart watch mode. so in this case, it will last less than my 935.
these aren't showstoppers by any stretch as the projected 24 hours of GPS will be enough for my backpacking trip and i can charge every 6-7 days rather than 8-10 days with my 935, but i'm a little disappointed.
i wonder if the battery capacity of the 945LTE is less than the 935, or perhaps the newer processor is a bit more power hungry.
i should note that i have PulseOx and wifi and LTE disabled, and while it's not an apples to apples comparison, i'm essentially running the same stuff (widgets and settings) as i am on my 935 but there are new things like the Body Battery that may or may not be using more power up.
what are your experiences? do you think the specs are legit? i know they say "up to"... i wonder if i should try a bare bones watch face with no seconds displayed and see what the basic burn rate is.
