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I’m curious what the various GPS units true battery life is. My Garmin Etrex Legend with Energizer batteries and WAAS and backlight off seems to last for about 8-9 continuous hours of use.
I know rechargeable batteries, WAAS, backlight, electronic compass, altimeter, etc will reduce battery life greatly.
What are your observations & with which unit?
If I had to estimate, I’d say I get about 25-30 hours or so on two AA batteries. I have a Garmin GPS72, WAAS enabled, backlight off.
Our Garmin 60C with 2 2500mAh energizer rechargable NiMh batteries lasts about 24-30 hours!!!
my 60cs is a battery miser too. Never really kept tabs on how long they last though.
My Legend with 1700-2500 mA rechargeables will last 10-15 hours. Course sometimes a fresh set seems to last 2-4, with no change in settings.. Not sure why. I usually don’t use WAAS because it usually doesn’t kick in unless I am in out in the open (no tree cover) where most Geocaches are not!
Sams has 8 2500 mA energizers for about 13-15 bucks. Generally, the higer the mAh (milliamps) the longer they will last.
12-14 hours on two AA Energizers in our Magellan Platinum.
Timberline Echoes
I just got back from judging our schools regional science fair … one project was on batteries and how long they last … the student timed them in hours/minutes in various electronic gadgets … and did it several times … Duracell beat out the other big name brands. Sure this was disposables and not rechargables, but still might be interesting to note, when applicable.
Here is a link to a review of rechargeable battery life. http://www.imaging-resource.com/ACCS/BATTS/BATTS.HTM
FYI, Cachew
Finding out about the various batteries is an easy task. Finding out how much current the various GPS receivers draw is not so easy. In my experience, the battery life expectancy reported by Magellan and Garmin is untrue. It also makes a big difference as to what mode the GPS is in, and how often the buttons are being pressed.
Yellow Etrex with regular Energizer batteries locked onto satellites without using any functions- batteries lasted about 15 hours.
Okay, I’m a geek. Here is the data from two Garmins, an eTrex Legend and a GPSMAP60C…
eTrex Legendw/ GPSr off…………..62 mA (switched on but not receiving)
GPSr on……………..140
plus WAAS……………148
plus backlight……….202
GPSMAP60Cw/ GPSr off…………..39 mA
GPSr on………………78
plus WAAS…………….80
plus 50% backlight……170
100% backlight……….188
You can get a rough idea of runtime by dividing the capacity of your cells (in milliamp-hours) by the load (in milliamps). I use old rechargeable 1700 mAh NimH cells. When these were brand new, I could probably expect to run the Legend with WAAS and no backlight for 11.5 hrs. The 60C would run almost double that or 21.2 hrs. The fact is, these batteries have seen many discharge/charge cycles and probably last only half that long.Typical (cheap) alkalines might power the Legend for 5.2 hours, and the 60C for 9.6 hours.
This is just a rule of thumb, because I am guessing a GPSr eats watts, not amps, so it also depends on the cell voltage throughout the discharge. As mentioned, a rechargeable cell’s age plays a huge part.
I didn’t expect the Legend to be that less efficient than the 60C. I would be interested in what load the electronic altimeter and compass add to the 60CS and other models.
I also expected WAAS load to be higher, based on what I have been seeing in the forums, but maybe I didn’t leave the GPSr locked on long enough for it to have an effect (the satellite screen did not indicate WAAS correction), I don’t know.
Sorry, no Magellans to test.
My ammeter hasn’t exactly been calibrated lately, so the data isn’t guaranteed. Your mileage may vary.
[This message has been edited by cachehedz (edited 04-22-2005).]
Just finished a project with a Nickel-Metal Hydride (NiMH) rechargeables so I will attempt to provide some ‘nerdy’ info to those who care.
Battery mfgs usually rate cells based on a certain discharge rate. This is usually something like 1% or 5% of the batteries rated capacity. For instance a 2100mAh tested with a load of 210mA should last for 10 hours. Similarly with a load of 1050mA, it should last for 2 hours. This is usually denoted in the battery datasheet as C or ‘capacity’. So 0.1C on a 2100mAh cell is 210 mA. A Garmin 60C discharges a 2100mAh cell at about .038C and should last about 26 hours.
NiMH cells have a certain ‘look’ to their discharge curves. That is they start out at about 1.4V drop quickly to about 1.25 volts and hover there for the longest time. The cells are considered ‘dead’ when they reach about 1.0V. This is how the battery gauge on your GPS works, it figures out where in the discharge curve you are and changes the indicator accordingly. This is also why on the newer GPS’s there is a setting for battery type. Primary cells (alkalines) have different looking curves than NiMH cells.
‘Batteries are like frogs.’ That’s what another engineer once told me. By this he meant they are a bit unpredictable, especially at the beginning and end of their life. So a 2100mAh cell at .038C may only last 4 hours on a full charge. Similarly it may last 30 hours on a full charge in the middle of its life. A typical cell will last between 500-1000 charges.
Energizer datasheets:
1700 mAh http://data.energizer.com/PDFs/nh15-1700mAh.pdf
2100 mAh http://data.energizer.com/PDFs/nh15-2100mAh.pdf
2500 mAh http://data.energizer.com/PDFs/nh15.pdfWas this useful?
[This message has been edited by TeamLotsacache (edited 04-23-2005).]
[This message has been edited by TeamLotsacache (edited 04-23-2005).]
[This message has been edited by TeamLotsacache (edited 04-24-2005).]
Good stuff guys! Nothing better than real measurements. Batteries are like frogs…. I will never forget that line.
So, if you see people at the campout with meter probes dangling from their gear…….
I just bought a Lowrance Ifinder Go, it adveritises 48 hours battery life on 2 AA, Still haven’t changed a fresh set in and been running ummmmmmmmm ‘bought 5 days now
Cool!Batteries are like frogs–I like that.
I have a calibrated Fluke 87 DMM and fresh Energizer alkaline batteries so I checked my Garmin GPS III, which is too old to have WAAS (1997). It updates the position, several internal timers, and other things every second, so the first number listed is the usual current use, the second number is the 1/10 second surge during an update, and the third number the average current use over 60 seconds, all in mA.
Idle (GPSr off): 41.6 / 63.2 / 45.1
Locking a Satellite: 72.4 / 96.0 / 85.0
Satellites Locked: 48.8 / 96.4 / 66.5 (except for 1 I couldn’t get a lock on)
50% Backlight: 92.0 / 142.8 / 108.0 (all but 1 locked)
100% Backlight: 122.4 / 177.2 / 143.0 (all but 1 locked)I did notice there would be a surge whenever I lost a satellite and the GPSr would try to find it, so I kept that out of the data. When caching under foliage satellites tend to get lost every so often, but each area has a different loss rate. I also didn’t worry about not getting a lock on one weak satellite signal, as that probably happens a lot when caching. If I had 12 clean signals I’d expect the current draw to be lower.
I built a power regulator for in the truck (while driving), so I really can’t say how long the batteries last on their own. I can say they last a lot longer when I use the regulator instead of constantly draining the batteries. (Pardon the reflexive pronoun usage.)
Battery voltage starting, (after above testing #1, recovery period test #1, recovery period test #2)
1: 1.597 (1.576, 1.577, 1.577)
2: 1.599 (1.579, 1.579, 1.580)
3: 1.602 (1.581, 1.581, 1.582)
4: 1.596 (1.575, 1.576, 1.576)The new batteries did lose some charge from testing, and the voltage slowly went back up as they recovered, as expected.
I’d like to thank those who provided battery links and testing.
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