Does Voltage Effect The Gpsr?

[+OKThumper]

I have a Garmin eTrex, and I have some questions.

 

Does the accuracy of the GPSr decrease as battery voltage decreases. Or, as the battery meter shows less capacity of the batteries does the accuracy decrease. I know that capacity and voltage or two different things but how does each effect the GPSr's accuracy.

 

Also, will using rechargeable (NiCd or NiMh, at 1.2v as opposed to the 1.5v for Alkaline) batteries in the eTrex have the same effect as low voltage Alkaline batteries?

 

If this has already been answered, I did not see it in a search.

 

Thumper

[+nincehelser]

I doubt it.

 

The digital portions (i.e. most of it) of your GPS pretty much swing one way or another. There is little middle ground. It either works, or it doesn't.

 

The analog portions could be impacted by a changing voltage, but I very much doubt it is detectable without sensitive test gear.

 

Alkalines slowly decrease in voltage over time. If there was a noticable decrease in accuracy over battery life, I expect someone here would have caught it by now.

 

It would also imply that fresh alkalines would allow more accuracy than most rechargables, because of the voltage differences inherent in their chemistry.

 

When the voltage drops low enough, all bets are off. Then your unit starts acting flakey. Accuracy is the least of your worries at that point.

 

George

[+geckoee]

The little ARM processor on the Garmin etrex actually uses the battery voltage to display the "capacity" You can see the voltage in the little firmware power up test (accessed by pressing the top two buttons while powering up the unit. If you do this don't press any other combination of buttons while it is powered up; that could reset the firmware, something you have to send it back to Garmin to repair. Just power it back down after ooh and awing at the internal temperature, and battery voltage.)

 

Edited for relevance:

 

Oh yeah, about the accuracy: Thinking about the way analog signal amps work... Maximum voltage difference... I'd say it can't be too much worse than 10% from full charge to dead.

Edited January 28, 2004 by geckoee

[+fivegallon]

I have a Garmin eTrex, and I have some questions.

 

Does the accuracy of the GPSr decrease as battery voltage decreases.  Or, as the battery meter shows less capacity of the batteries does the accuracy decrease.  I know that capacity and voltage or two different things but how does each effect the GPSr's accuracy.

 

Also, will using rechargeable (NiCd or NiMh, at 1.2v as opposed to the 1.5v for Alkaline) batteries in the eTrex have the same effect as low voltage Alkaline batteries? 

 

If this has already been answered, I did not see it in a search.

 

Thumper    

Try this quote http://forums.Groundspeak.com/GC/index.php...iew=getlastpost ,

from this topic http://forums.Groundspeak.com/GC/index.php...913&hl=alkaline

[+Prime Suspect]

The little ARM processor on the Garmin etrex actually uses the battery voltage to display the "capacity" You can see the voltage in the little firmware power up test (accessed by pressing the top two buttons while powering up the unit. If you do this don't press any other combination of buttons while it is powered up; that could reset the firmware, something you have to send it back to Garmin to repair. Just power it back down after ooh and awing at the internal temperature, and battery voltage.)

 

Edited for relevance:

 

Oh yeah, about the accuracy: Thinking about the way analog signal amps work... Maximum voltage difference... I'd say it can't be too much worse than 10% from full charge to dead.

Resetting the firmware shouldn't require a trip back to the factory. Under certain circumstances, it could cause it to become miscalibrated, but if you do it indoors, where it can't get a signal, you don't have to worry about that. The unit will recalibrate itself over time.

 

You will, of course, have to reload any OS upgrades, waypoints, routes, etc., as they will be lost. You'll also have to reacquire almanac data, as well.

[+geckoee]

The little ARM processor on the Garmin etrex actually uses the battery voltage to display the "capacity"  You can see the voltage in the little firmware power up test (accessed by pressing the top two buttons while powering up the unit.  If you do this don't press any other combination of buttons while it is powered up; that could reset the firmware, something you have to send it back to Garmin to repair.  Just power it back down after ooh and awing at the internal temperature, and battery voltage.)

 

Edited for relevance:

 

Oh yeah, about the accuracy:  Thinking about the way analog signal amps work... Maximum voltage difference... I'd say it can't be too much worse than 10% from full charge to dead.

Resetting the firmware shouldn't require a trip back to the factory. Under certain circumstances, it could cause it to become miscalibrated, but if you do it indoors, where it can't get a signal, you don't have to worry about that. The unit will recalibrate itself over time.

 

You will, of course, have to reload any OS upgrades, waypoints, routes, etc., as they will be lost. You'll also have to reacquire almanac data, as well.

Yeah it looks like a trip back to Garmin may not be nessisary, Garmin dose say on there web page not to load the wrong firware as that can hose the unit.

 

3rd Party FAQ

Garmin Info

[+RJFerret]

Does the accuracy of the GPSr decrease as battery voltage decreases.

 

Simple answer: No.

 

Complex answer: The voltage of recievers has no impact on the signal received. That onus is on the transmitter. You can however use an amplified antenna, which would boost the strength of weak signals--but your GPS accuracy is not affected by power levels.

 

Enjoy,

 

Randy

 

(Sorry General, our smart bomb didn't fly down the chimney because Private Reed was using the batteries in her, um, er, personal appliance last night.)

[+OKThumper]

OK, thanks guys. I had read the other post about batteries but did not see a specific answer to my question. But ya'll made it clear that no loss of performance would be noticed. By the way I have a lot of NiCd and NiMh batteries in sub-c and AA sizes as I use them in my other hobby RC cars. When you spend between $50 and $100 from a matched set of six sub-c's you tend to get a little anal about the care and feeding of your cells.

 

Thanks

Thumper

[+geckoee]

Does the accuracy of the GPSr decrease as battery voltage decreases.

 

Simple answer: No.

 

Complex answer: The voltage of recievers has no impact on the signal received. That onus is on the transmitter. You can however use an amplified antenna, which would boost the strength of weak signals--but your GPS accuracy is not affected by power levels.

 

Enjoy,

 

Randy

 

(Sorry General, our smart bomb didn't fly down the chimney because Private Reed was using the batteries in her, um, er, personal appliance last night.)

I trouble shoot antennas, and microwave signal processors, so I like to pretend I know what I am talking about

 

After the signal is received by the antenna sometimes there is some passive processing done to it to limit the band, and determine the phase and possibly other things. At some point the signal needs to be amplified in order to be interpreted by the MCU. (sometimes this amplification is done before processing) A lower voltage level means a smaller window for measurement, and more background noise.

 

So voltage level has some, but limited impact on signal integrity.

 

Check out this URL for more info.

The first stage after the antenna is a 10dB gain amp!

[2oldfarts (the rockhounders)]

The only time I have noticed any problems was when I let the batteries get down to the last 15 minutes (approximately) of juice. Then the GPSr was reading all over the place while I was standing still.

 

John

[+GeckoGeek]

Does the accuracy of the GPSr decrease as battery voltage decreases.

While I see a number of replies, I thought I'd throw in my opinion. While I wouldn't expect there to be any effect, I've been around electronics long enough to know some strange things can and do happen so I wouldn't rule anyone's personal observation.

 

While I wouldn't expect a linear decease in accuracy with battery voltage, I can easily see that when the battery is at end of life the unit may be suffering from some kind of voltage starvation and causing problems that show up as decreased accuracy. This problem could vary from unit to unit even within the same model. Just a question of what quits first - the power shutdown due to low voltage or some kind of system malfunction.

[phern47]

I went ice fishing today. I knew my batteries were getting weak but I did not change them. The fishing site is 3 km from my house. My old Garmin acquired it's position quite nicely and off I went with the Garmin on my dash. When I got to the site, I got out of the car I turned off the Garmin and put it in my pocket. When I finally got all set up, I turned the Garmin back on. The battery level was below 1/4. The Garmin was on "battery saver". Anyway, after a couple of minutes, I didn't have any signal strength from the satellites so I turned off the GPS. When I got home, I could see my route. It was "dead on".

Now...2 questions.

1. When in battery saver mode, does acquisition time increase?

2. When batteries are very low, does acquisition time increase?

[+Right Wing Wacko]

<snip>

 

I got out of the car I turned off the Garmin and put it in my pocket.

 

<snip>

TURN OFF THE GPSr? That does not compute! Is that Legal?

[phern47]

I had to put it into my pocket in order to carry all of my fishing equipment out onto the ice. Because it was "low tide" it was downhill on sheer slippery ice.

[+crzycrzy]

My similar product works like a champ right up until it goes dead.