Do weak batteries affect GPS receiver accuracy?

[BearcatFan]

Seemed like my Magellan explorist 300 was off by 100' or so today when I was out geocaching. I marked my car, and when I got back to it GPSr showed it 100' away from where it really was. My battery indicator showed I had about 1/4 power left. Do GPsr get less accurate with weak batteries? thanks for any assistance

[+W7WT]

I always thought they did but haven't ran any tests. Both my 76S and 76C seem to be off when the battery is low. They seemed to be more accurate when I put new batteries in. Could be my imagination. I can get a big pack of 40 AA's at Costco for around $10 or so. I always change batteries when they show less than 4 bars. I also have the Etrex HCx which has a very long battery life and I change the battery and calibrate the compass when the battery shows less than all the bars. Dick

[+JohnnyVegas]

I saw this happen from time with some of the older GPS'rs like my Magellen Meridian gold and my old e-trex. But the batteries had to be almost totaly depleted. With WAAS and the improved GPS chipsets this may no longer be a problem.

[BearcatFan]

Thanks a lot for the input.

 

I know my explorist 300 was off, because we were looking for a cache that we previously did not find, and it showed it 80' away from when we were last there with strong batteries. My GPS showed tracking 8 sattelites so don't think that was the issue. We were in a forest however. Battery meter has about 5 bars when fully charged and I was down to 2. Seems like me since these things are digital that they would either work or not, but guess not. Embarassed to say that I am an electrical engineer (BSEE 1987) and today's technology gets the best of me.

 

My family (wife and 10 year old daughter) and I just started geocaching 4 months ago, and I think it is the most fun we've had together. I bought my GPS to ensure I would not get lost while deployed to Iraq in 2005-2006, but did not use it much over there. Did not start geocaching until I got a nuvi 205w for the car for Christmas. Wish we would have known about it prior to our roadtrip from Anchorage, Alaska, to San Antonio, Texas, in 2007 as I am sure there were some fun caches along the way.

[jholly]

Thanks a lot for the input.

 

I know my explorist 300 was off, because we were looking for a cache that we previously did not find, and it showed it 80' away from when we were last there with strong batteries. My GPS showed tracking 8 sattelites so don't think that was the issue. We were in a forest however. Battery meter has about 5 bars when fully charged and I was down to 2. Seems like me since these things are digital that they would either work or not, but guess not. Embarassed to say that I am an electrical engineer (BSEE 1987) and today's technology gets the best of me.

 

My family (wife and 10 year old daughter) and I just started geocaching 4 months ago, and I think it is the most fun we've had together. I bought my GPS to ensure I would not get lost while deployed to Iraq in 2005-2006, but did not use it much over there. Did not start geocaching until I got a nuvi 205w for the car for Christmas. Wish we would have known about it prior to our roadtrip from Anchorage, Alaska, to San Antonio, Texas, in 2007 as I am sure there were some fun caches along the way.

 

It is mostly digital. At least part of the front end has to be analog. I think it has a lot to do with the unit and the design of the unit. I have a 76CSx and don't really notice much problems even down to 2 of 4 bars. I really can't say much about batteries below that because I rarely get that low. But the time or two I did I can't recall haveing a high DNF rate. For what it is worth I use NiMH batteries and always leave in the morning with them fully charged. When I come home in the afternoon the battery indicator is generally at least 3 bars.

 

Jim

[BGSkierNC]

My eTrex summit would be low on power and point all over the place when near a geocache. Not just the arrow direction, but the distance would jump 100-200 feet, too. Changing to fresh batteries cleared up those problems quickly.

[yogazoo]

My eTrex summit would be low on power and point all over the place when near a geocache. Not just the arrow direction, but the distance would jump 100-200 feet, too. Changing to fresh batteries cleared up those problems quickly.

 

My guess would be that the cycling of power (needed to change batteries, obviously) would be more responsible for the more steady operation afterwards than the charge state of the batteries.

 

It is my observation that most people who design electronics, design them to use less power than what has been designed to supply that power. Hence the buffer of extra power supplied by the batteries (battery life) and hence a battery meter. Components usually have forwarding requirements and at a certain (usually low) level will function as normal. When the forward power tolerance of the components is met, the components operate normally, when the forwarding power is not met, the unit turns off . As far as the functions tapering off, well generally speaking, electronic components just don't work like that. Digital components don't operate like motors, spinning slower and slower as the power decreases.

 

In my educated opinion: It is an absolute WASTE to change batteries after just one bar has vanished or before the unit shuts off. PERIOD.

 

As we all bore witness to in the early release of the Colorado, battery life is digitally controlled by firmware before the components even get a chance to chime in (power down). The early batt life on the Colorado was poor because the unit's firmware told it to shut down at a power level way too high. The forwarding potential of the components was at a much lower level and once Garmin tweaked the firmware the batt life imporved dramatically. The reason the battery meter on the Oregon is garbage is because they have the discharge points all wrong in the firmware. Currently the batterys in the Oregon dishcarged at about 15% are recognized by the firmware as being at about 50% thats why the meter shows you with half the life very shortly after the unit being on. BUT the batteries are stuck forever at that two bar level and last just as long as if Garmin would have gotten the mid point right. Garmin can make it accurate and probably will in future firmware updates. As far as JohnnyVegas experiencing poor operation in the meridian series, the firmware battery threshold may have been set slightly low providing a brief period of less than stellar operation but still within the forwarding tolerance of the components.

 

Think of batteries as a water bladder(camelback). If you remove the stop-cock and allow the water to flow out through the tube you will get a steady and constant stream of water from the tube no matter how much water is in your water bladder(power). That flow will remain steady and constant until there is absolutly no water at which point the flow will stop altogether. Same with electronics, the power stored in the batteries flows out at a low, constant stream until they no longer meet the flow requirements = dead batteries/electronics shut down.

 

Changing batteries before they're read as dead is a waste. It would be like throwing a half empty water bladder away before the rest of the water trickles out of the tube. Rediculous!

Edited January 21, 2009 by yogazoo

[+manxmann]

Seemed like my Magellan explorist 300 was off by 100' or so today when I was out geocaching. I marked my car, and when I got back to it GPSr showed it 100' away from where it really was. My battery indicator showed I had about 1/4 power left. Do GPsr get less accurate with weak batteries? thanks for any assistance

I have a Garmin GPS60 and usually run it until it shuts down due to "low battery" power. I always take spare batteries specifically to allow me to do this. I have never noticed any change in accuracy that I could relate to battery status. There are, however an awful lot of other influencing factors which I am sure you would be familiar with.

 

No expert though !