Batteries and accuracy?

June 6, 2015

For a few weeks now, Ive been using the Garmin rechargeable battery pack in my GPSMap 64st. Before that it was straight up lithium. Now I've noticed my accuracy declining, all I ever used to see was 10 feet. Besides that, I've seen post in here by Garmin users that were advised by Garmin support, not to use the battery saver feature to improve accuracy. I like the convenience and cost saving of the battery pack but not if it's trashing my accuracy. Does anyone have any insight on this or is it my imagination?

June 6, 2015

I use rechargeables in my Oregon 450 and it seems to work fine. They don't last as long though.

8.6k · June 6, 2015

Have you actually checked the accuracy... or are you relying on that number displayed on the screen?

That number displayed on the screen is not true "accuracy". It is Estimated Positional Error (EPE) -- a number derived at by mathematical computations involving a wide array of variables.

If that number is 10, 65, or 250... it does not mean that the device is truly off by 10, 65 or 250 ft.

It does mean that the target coordinates would be (somewhere) within a circle of that diameter (in feet).

All GPSr units have EPE, whether they display that figure or not. It is the way the system (satellite constellation, signals received, signal strength, interference and more... ) as a whole functions.

Older generation GPSr units used to label that figure as EPE -- today it seems, they just stick the number there by itself or even say "accuracy (X)XX ft." I guess they changed it because so few actually understood what EPE is or does.

Go ahead and do a Google search for Estimated Position Error and see what kind of stuff pops up.

You'll find it either extremely interesting or intensely boring. :lol:

With all of that said, it IS possible that battery strength can affect EPE. This is primarily because of the mixing signal transmitted by the device (yes, they do transmit a signal, a very minute signal -- all radio signal RECEIVERS do). If your batteries are not "up to snuff", the reduced power output *could* affect signal reception, in theory -- but at such a reduced power level, your device would be running on fumes anyway.

Should you feel inclined to check your unit's true accuracy, you should perform a number (a dozen +) of tracks to a single coordinate setting and mark that spot each time you arrive at it. That will give you an idea of just how accurate your unit is or is not. Repetitive duplication would equate to true "accuracy".

Remember too, you have a consumer-grade device. It simply is not designed for absolute, pin-point accuracy. Those units exist, but most of us cannot afford them (surveyor, military or other governmental-type GPS devices).

19k · June 6, 2015

Have you actually checked the accuracy... or are you relying on that number displayed on the screen?

That number displayed on the screen is not true "accuracy". It is Estimated Positional Error (EPE) -- a number derived at by mathematical computations involving a wide array of variables.

If that number is 10, 65, or 250... it does not mean that the device is truly off by 10, 65 or 250 ft.

It does mean that the target coordinates would be (somewhere) within a circle of that diameter (in feet).

All GPSr units have EPE, whether they display that figure or not. It is the way the system (satellite constellation, signals received, signal strength, interference and more... ) as a whole functions.

Older generation GPSr units used to label that figure as EPE -- today it seems, they just stick the number there by itself or even say "accuracy (X)XX ft." I guess they changed it because so few actually understood what EPE is or does.

Go ahead and do a Google search for Estimated Position Error and see what kind of stuff pops up.

You'll find it either extremely interesting or intensely boring.

With all of that said, it IS possible that battery strength can affect EPE. This is primarily because of the mixing signal transmitted by the device (yes, they do transmit a signal, a very minute signal -- all radio signal RECEIVERS do). If your batteries are not "up to snuff", the reduced power output *could* affect signal reception, in theory -- but at such a reduced power level, your device would be running on fumes anyway.

Should you feel inclined to check your unit's true accuracy, you should perform a number (a dozen +) of tracks to a single coordinate setting and mark that spot each time you arrive at it. That will give you an idea of just how accurate your unit is or is not. Repetitive duplication would equate to true "accuracy".

Remember too, you have a consumer-grade device. It simply is not designed for absolute, pin-point accuracy. Those units exist, but most of us cannot afford them (surveyor, military or other governmental-type GPS devices).

And from what I've read, there is no official formula for EPE... it varies between manufacturers, and I suspect, even between models by the same manufacturer. And accuracy depends a great deal on the position of the satellites (it does NOT depend upon clouds or rain or power lines, as some may claim).

I don't know anything about this battery saving function, but I'm guessing that it simply takes fewer samples, and if that is true, and you are moving, it won't be updating your position as often, and I can see how that might make it tougher to locate GZ.

June 6, 2015

I used to have horrendous error problems. The GPS would suddenly ask me if I wanted to switch to automotive mode, because it was travelling across the nearby lake at 40 MPH (~64 KPH). After several miles, it would usually settle back on my current location, but I never knew when it was going to take one of these "trips."

After living with this for years, I discovered that it was caused by my camera. I have since replaced both GPSr and camera, and I don't have the problem at all any more, but I always keep in mind that other electronics can and under the right conditions, will interfere.

1.1k · June 8, 2015

I use non-rechargeable batteries in my 13+ year old GPS V. Not only that I use ones that no longer will work in other devices but seem to work fine in the GPS V.

Yes I know it's an old unit and that there are many newer ones but it works great, has great accuracy and is very rugged. :rolleyes:

19k · June 8, 2015

I use non-rechargeable batteries in my 13+ year old GPS V. Not only that I use ones that no longer will work in other devices but seem to work fine in the GPS V.

Yes I know it's an old unit and that there are many newer ones but it works great, has great accuracy and is very rugged.

Likewise. NiHM batteries, always freshly charged in a 15 minute charger (not the best for the life of the cells, but fine with me) before I leave the house. They last me all day.

Of course, the OP is also using rechargable batteries (the Garmin rechargeable battery pack). The question has to do with the power-saving mode, not the type of battery.

To the OP: Is that what they refer to as UltraTrac mode?

Speed, distance, and track data accuracy are reduced in UltraTrac mode.

TIP: For extended activities, you should consider other battery saving options:

Maximizing Battery Life

Shorten the backlight timeout (Backlight Settings).

Shorten the timeout to watch mode (Power Save Timeout Settings).

Turn off activity tracking (Activity Tracking).

Select the Smart recording interval (Data Recording Settings).

Turn off GLONASS (Changing the Satellite Setting).

Turn off the Bluetooth^® wireless feature (Turning Off Bluetooth^® Technology).

Turn off the Wi‑Fi^® wireless feature (Turning Off Wi‑Fi^® Technology).

Edited June 8, 2015 by knowschad

1.9k · June 8, 2015

I use a Garmin GPSMap62 -- I do feel that my accuracy goes down when my batteries get low. I use standard Alkaline batteries, and try to carry a spare set just in case.

2.4k · June 10, 2015

I use rechargeables in my Oregon 450 and it seems to work fine. They don't last as long though.

Just a thought... in the past I've found that people start out with alkaline batteries 1.5 v, but later switch to rechargables, say NiMH which are nominally 1.2 v... BUT forget to check the battery type settings. This can cause the device to show low battery early on. There are reasons for that, but it is techy and not a quick answer... Just check. Also make sure that the batteries are freshly charged... if they sit a while, they can self discharge or simply lose charge and thus deplete fairly quickly. Sometimes happens to me when I forget to top them up after a caching layoff period..

Hope that might help.

Doug 7rxc

19k · June 10, 2015

I use rechargeables in my Oregon 450 and it seems to work fine. They don't last as long though.

Just a thought... in the past I've found that people start out with alkaline batteries 1.5 v, but later switch to rechargables, say NiMH which are nominally 1.2 v... BUT forget to check the battery type settings. This can cause the device to show low battery early on. There are reasons for that, but it is techy and not a quick answer... Just check. Also make sure that the batteries are freshly charged... if they sit a while, they can self discharge or simply lose charge and thus deplete fairly quickly. Sometimes happens to me when I forget to top them up after a caching layoff period..

Hope that might help.

Doug 7rxc

Good point. As I said above, NiMH last at least a full day (plus a bit) in my Oregon 450, but... but... the shelf life on a charge is not very long, so you do want to charge them just before heading out. Or, at least, the night before.

15.3k · June 10, 2015

I've been using low self-discharge NiMH batteries (Eneloop) in various devices. They're still only 1.2V, but they do hold their charge for a long time, even in devices that don't get used much.

June 10, 2015

I use rechargeables in my Oregon 450 and it seems to work fine. They don't last as long though.

Just a thought... in the past I've found that people start out with alkaline batteries 1.5 v, but later switch to rechargables, say NiMH which are nominally 1.2 v... BUT forget to check the battery type settings. This can cause the device to show low battery early on. There are reasons for that, but it is techy and not a quick answer... Just check. Also make sure that the batteries are freshly charged... if they sit a while, they can self discharge or simply lose charge and thus deplete fairly quickly. Sometimes happens to me when I forget to top them up after a caching layoff period..

Hope that might help.

Doug 7rxc

No, I've got the right battery type selected, thanks. I think it's more than I don't use the unit every day so the batteries sit for longer.

19k · June 10, 2015

I've been using low self-discharge NiMH batteries (Eneloop) in various devices. They're still only 1.2V, but they do hold their charge for a long time, even in devices that don't get used much.

Yeah, I know the battery geeks speak very highly of those. I have no need for anything better, though. What I've got works 100% for me, so why pay more? I also use a dreaded 15 minute charger. A set of AAs lasts me at least a year with that.

19k · June 10, 2015

I use rechargeables in my Oregon 450 and it seems to work fine. They don't last as long though.

Just a thought... in the past I've found that people start out with alkaline batteries 1.5 v, but later switch to rechargables, say NiMH which are nominally 1.2 v... BUT forget to check the battery type settings. This can cause the device to show low battery early on. There are reasons for that, but it is techy and not a quick answer... Just check. Also make sure that the batteries are freshly charged... if they sit a while, they can self discharge or simply lose charge and thus deplete fairly quickly. Sometimes happens to me when I forget to top them up after a caching layoff period..

Hope that might help.

Doug 7rxc

No, I've got the right battery type selected, thanks. I think it's more than I don't use the unit every day so the batteries sit for longer.

That would do it. As I said above, you need to recharge them before you go out. She shelf life is the trade-off. There's always a trade-off.

3.6k · June 11, 2015

I stopped using rechargeables when spooking things were happening. Like the GPS would shut off when I crossed a specific spots. I tried driving around and everything would be fine. I drive over or near those spots and they would shut off again. Most of times it would do this near a utility box or crossing RR tracks. It became a real bother and after putting in regular batteries I didn't have that problem again.

2.6k · June 11, 2015

I use low self-discharge NiMH batteries (Eneloop) in my Oregon 600. I've not noticed any loss of accuracy or anything strange when the batteries get low. Nor any interference from other devices or power lines etc.

19k · June 11, 2015

I stopped using rechargeables when spooking things were happening. Like the GPS would shut off when I crossed a specific spots. I tried driving around and everything would be fine. I drive over or near those spots and they would shut off again. Most of times it would do this near a utility box or crossing RR tracks. It became a real bother and after putting in regular batteries I didn't have that problem again.

Yeah, that's pretty spooky. Doesn't make any sense to me.

19k · June 11, 2015

I use low self-discharge NiMH batteries (Eneloop) in my Oregon 600. I've not noticed any loss of accuracy or anything strange when the batteries get low. Nor any interference from other devices or power lines etc.

I could see that if (*IF*) a GPS had a feature to switch to a power-saving mode automatically when the battery fell below a given level that accuracy could be affected. To the best of my limited knowledge, though... none do.

2.4k · June 11, 2015

I use low self-discharge NiMH batteries (Eneloop) in my Oregon 600. I've not noticed any loss of accuracy or anything strange when the batteries get low. Nor any interference from other devices or power lines etc.

I could see that if (*IF*) a GPS had a feature to switch to a power-saving mode automatically when the battery fell below a given level that accuracy could be affected. To the best of my limited knowledge, though... none do.

What many devices have when set for rechargables... is a circuit that monitors the voltage level.

You don't want them to drop below 1 volt per cell in most cases. Nimh batteries for example start out (fresh charge) just a bit higher than 1.2 volts per cell. It is high because of the required charge voltage, and fairly quickly drops to the 1.2 volts level. Even in use a common type Nimh will hold a near constant voltage until it is about to 'die'. Then it drops quite quickly. The monitor if it exists watches for the sudden drop off to begin and shuts the device down. I've always suspected (not proven) that the weird stuff some observe is due to the monitor being less than optimal in its settings or the same for the battery cells. I'm not an expert there, but they are strange creatures in my mind.. I have 4 that became totally inert when 'lost' for a while... and needing a recharge. 0 volts and no sign of taking a charge from the factory charger... I tried an experiment to see what happens using older NiCd procedures for a start point of experimentation... end result is 4 batteries that hold charge quite well, and often at a higher voltage longer. I don't use them for critical stuff, but they hold up for non critical tasks while I watch. Add that they were all (including the ones I use caching) bought in the late 90's on sale, and I'm happy that any are working. They were bargain type quality... don't see them around any more though. I do know that slow charging is better than fast though... chargers all vary in specs and quality.

Doug 7rxc

19k · June 11, 2015

I use low self-discharge NiMH batteries (Eneloop) in my Oregon 600. I've not noticed any loss of accuracy or anything strange when the batteries get low. Nor any interference from other devices or power lines etc.

I could see that if (*IF*) a GPS had a feature to switch to a power-saving mode automatically when the battery fell below a given level that accuracy could be affected. To the best of my limited knowledge, though... none do.

What many devices have when set for rechargables... is a circuit that monitors the voltage level.

You don't want them to drop below 1 volt per cell in most cases. Nimh batteries for example start out (fresh charge) just a bit higher than 1.2 volts per cell. It is high because of the required charge voltage, and fairly quickly drops to the 1.2 volts level. Even in use a common type Nimh will hold a near constant voltage until it is about to 'die'. Then it drops quite quickly. The monitor if it exists watches for the sudden drop off to begin and shuts the device down. I've always suspected (not proven) that the weird stuff some observe is due to the monitor being less than optimal in its settings or the same for the battery cells. I'm not an expert there, but they are strange creatures in my mind.. I have 4 that became totally inert when 'lost' for a while... and needing a recharge. 0 volts and no sign of taking a charge from the factory charger... I tried an experiment to see what happens using older NiCd procedures for a start point of experimentation... end result is 4 batteries that hold charge quite well, and often at a higher voltage longer. I don't use them for critical stuff, but they hold up for non critical tasks while I watch. Add that they were all (including the ones I use caching) bought in the late 90's on sale, and I'm happy that any are working. They were bargain type quality... don't see them around any more though. I do know that slow charging is better than fast though... chargers all vary in specs and quality.

Doug 7rxc

Does "that the weird stuff some observe" include shutting the GPS down when you cross a RR track?

Edited June 11, 2015 by knowschad

June 11, 2015

I stopped using rechargeables when spooking things were happening. Like the GPS would shut off when I crossed a specific spots. I tried driving around and everything would be fine. I drive over or near those spots and they would shut off again. Most of times it would do this near a utility box or crossing RR tracks. It became a real bother and after putting in regular batteries I didn't have that problem again.

Huh. That's interesting. My Oregon shuts down sometimes for no reason at all. I wonder if it's my batteries?

4.1k · June 11, 2015

For a few weeks now, Ive been using the Garmin rechargeable battery pack in my GPSMap 64st. Before that it was straight up lithium. Now I've noticed my accuracy declining, all I ever used to see was 10 feet. Besides that, I've seen post in here by Garmin users that were advised by Garmin support, not to use the battery saver feature to improve accuracy. I like the convenience and cost saving of the battery pack but not if it's trashing my accuracy. Does anyone have any insight on this or is it my imagination?

I stopped using the Garmin battery pack with my Oregon 600 and switched to higher powered Eneloops (with a small plastic strip underneath them do that I can recharge them inside the unit). My reason for switching had more to do with increasing the length of the charge rather than accuracy, but I have grown more confident about the Oregon's accuracy since then. I have never associated the two, but now I wonder, although not enough for me to run comparisons.

21.9k · June 11, 2015

I am moving this thread from the Geocaching Topics forum to the GPS forum.

June 12, 2015

I am moving this thread from the Geocaching Topics forum to the GPS forum.

Over the years, some Garmin Handheld GPS users have reported electronic compass drift that corresponds to unregulated battery voltage decline.

2.4k · June 13, 2015

Does "that the weird stuff some observe" include shutting the GPS down when you cross a RR track?

I don't know about other models, but our SAR group had some eTrex Legends that had really weak springs in the battery compartment... I think those could have done that... until you stretched the springs out a bit to increase the tension.

The also liked drawing lines across the screen and once in a while, fading out of view.

So who knows what's possible?

Doug 7rxc

Batteries and accuracy?

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