This is the test data from Batteriser's Video:
...
The upper trace (red) shows that as the test continues the battery current rises. This is a characteristic of a switching power supply. The switching power supply is drawing constant power from the batteries. The step is when the Garmin GPS reduces the brightness to prolong battery life.
Yeah, I'm still a bit perplexed as to exactly what is happening there on their graph, that result has never made any sense at all to me. Beyond completely fudging it on their part with extra resistance or starting with partially discharged batteries (can't tell since we see only current, not the starting cell voltage) or somesuch, my best guess is that because their screen tapper wasn't over the OK button on the alkaline battery feature notification like it was during 5ky's tests, the GPS runs until the message is displayed, then because the OK is never pressed it eventually times out and powers down or something.
Perhaps 5ky can shed some light on that for us as to what might have been happening there.
5ky, Does the unit eventually shut itself off or go into some sort of standby mode if you
don't press the OK button when the backlight reduction notice appears? According to their graph it looks like it took about 25 minutes from the reduction in current point. (If anything on that graph can be believed, that is...)
5ky test results show that the time scale on this graph is wrong. The GPS should run for about 10 hours.
Yeah, something certainly makes no sense with that upper, red graph. Either they completely fudged something to do with the test itself or the timescale on the results or something like my hunch above must be occuring. If they really measured that first test with fresh cells and didn't fudge the timescale, they must have some
very significant extra resistance in there for the GPS to have seen such low voltages at its input so quickly.
As for total runtime, since they were using the Alkaline setting they should have got more like 17 hours total with the reduced backlight, not 10 hours, shouldn't they? The time to backlight reduction should be more like 6 hours according to 5ky's data rather than the hour and a half or so that they seem to have observed.