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Etrex Battery Save mode?

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Does anybody know exactly how the "Battery Save" mode in the Garmin Etrex works?


I went out to search my first stach yesterday, and lost plenty of time because the unit wasn't able to guide me precicely. Ik kept indicating the location was within 40-50 meters, not closer, but continuesly changed heading, sometimes switching 180°... icon_confused.gif


I blamed the dense foliage ("Boomerang" stach in Belgium), and was near to abandon, when I found out the unit was in "Battery Save" mode. I put it in "Normal" mode, and then my unit directed me without problem to right spot, about 80 meters from where I was first searching... It brough me within 6 meters of the stach. icon_razz.gif


I afterwards went for the "Ocean Treasure" stach, and found it immediately, with again 5-6 meters precision.


Just wondering... icon_confused.gif




Don't Dream It... Be It!

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Battery saver mode basically powers up the receiver at regular intervals, then powers back down until the next interval. I don't reall how much time the interval was. Sounds kinda lame in my thinking, but evidently someone thought it was a nice feature. I suppose it would be ok in a plane or a long distance car trip, to give a general idea of the path you took. Definately would not be the mode to use for geocaching!

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Sorry for doubling some info here, but the first reply wasn't there, when I started writing this one! icon_eek.gif

In normal mode, the eTrex reads the satellites once very second.

Running the receivers is a power consuming task, so in battery save mode, it reads the position, then skips that for three or four seconds, before updating again.


This means that battery life is extended, since the higher consumption isn't present all the time. On the other hand, it also means that new updates of the position doesn't come that often. So, if you are walking in one direction, the unit reads your position (and, by comparing with your previous position, figures out your heading) and you happen to make a sharp turn, the unit will not know that for some seconds yet.

Now, to make things worse, assume that the next satellite reading is unsuccessful, due to dense tree cover. That means that another period, without updates, passes. Meanwhile, the unit still thinks you are going on in your previous direction, although you aren't. An eTrex will pretend that it knows where you are going up to 30 seconds, before it admits to loosing the satellite lock.


In a troublesome environment (heavy foilage), this behaviour comes and goes all the time.

On the other hand, if you use normal mode, updating happens more frequently. Even if some updates fail, chances are better that you will get a reading now and then, a reading that allows the unit to determine where you are going.


I use my unit like this: Normally, I run in Battery Save mode. When in the car, and powered externally, it switches to normal mode anyway.

When I'm pretty close to the cache, I switch to normal mode, and turn on the compass (Summit/Vista only).


Once I've found the cache, I turn the compass off, and revert to battery save mode again.


How much running time you get on your batteries depends on temperature, batteries and so on, but for a Vista, it's related like this:


Battery save mode: 12 hours.

Normal or save mode+compass: 9 hours.

Normal and compass: 6 hours.


This is assuming Garmin's figure for battery save mode (12 hours) is correct.



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