60CSx battery lifetimes

[DougPaul]

Garmin 60CSx battery lifetimes

The discussion about battery lifetimes in another thread (http://www.vftt.org/forums/showthread.php?t=35852) piqued my interest, so I did a few experiments using two 60CSx's and discovered some things that may interest users and prospective purchasers of same.

Summary:
Tests on stationary 60CSx's indicated that battery-saver mode increases the battery life of the GPSes by 45-80% but increases the error by a factor of ~3 (to 28.6m). (Garmin's rating is 10m.)

The tests also indicated that Garmin has modified newer 60CSx's to increase the battery life by 20-25% and fix the problem with new lithium batteries.

The best battery lifetimes achieved were 26.3 hrs for normal mode and 47.5 hours for battery saver mode using 2500 mAh NiMH batteries (Garmin's rating is 18 hours.)

The details:
The older one (GPS1) was purchased in Nov 2006 (ser no 74xxxxxx) and the newer one (GPS2) purchased in Mar 2010 (ser no 118xxxxxx). Both were running Software v4.00 and GPS Software v2.90.

The manual (Aug 2007) gives a battery life of "Up to 18 hours (typical use)" for alkaline batteries, which have a typical capacity of 2300-2500 mAh. (The manual also includes a note that temperature and use of the backlight, compass, and tones can affect battery life.)

The first set of experiments compared GPS-normal and GPS-battery-saver modes using Sanyo Eneloop AA NiMH batteries, rated 2000 mAh and measured* between 2000 and 2100 mAh. (The batteries were run thorough several discharge-charge cycles to make sure they were at peak capacity.) The GPSes were stationary, with a somewhat degraded skyview (indoors in a 1-story wood frame building), a constant lock, compass off, backlight off, and WAAS off.

        Battery lifetime, hrs
        norm    batt-sav
GPS1    17.1     25.2
GPS2    22.0     37.3

The second set of experiments was the same except that it used LaCrosse 2600 AA NiMH batteries, rated at 2600 mAh and measured* between 2440 and 2510 mAh.

        Battery lifetime, hrs
        norm    batt-sav
GPS1    20.4     31.7
GPS2    26.3     47.5

Since these batteries have a similar capacity to alkalines, I would expect these numbers to be similar to those for alkalines. However, I did not test this conjecture.

* These capacity measurements were made at a 500 mA discharge rate. The GPSes are drawing average currents of 50-120 mA. Capacity measurements at these rates would likely give slightly higher capacities.

The above experiments indicate that battery-saver mode can increase the battery life by 45-80% and that battery life for the new unit is 20-25% greater than for the old unit.

A problem the old 60CSx is that one cannot use new lithium cells in it--see http://www.vftt.org/forums/showpost.php?p=158401&postcount=4. This appears to be fixed in the new 60CSx. (Info from Peakbagr, verified by me.)

The battery-saver mode offers some attractive battery lifetime increases, but decreases the accuracy of the GPS. To evaluate the decreased accuracy, I measured the scatter of GPS locations reported every 30 seconds by two side-by-side units for the same 17 hour period. The measure is 2*2Dsd (2Dsd = 2 dimensional standard deviation) which is gives approximately 95% probability of being within the given distance of the true location (The standard spec for consumer GPSes.) The GPS locations and conditions were the same as above.

Garmin spec:      10m
GPS-norm:         10.3m
GPS-batt-savr:    28.6m

So the battery-saver mode of 60CSx appears to increase the errors by a factor of around 3. (Note this is for stationary GPSes with a somewhat degraded skyview. The factor could be different for different skyviews or if the GPSes were in motion. This may also depend on the GPS model--my original eTrex Vista tended to lose lock if I used battery-saver mode. The 60CSx's in this experiment did not lose lock during the test period.)

FWIW, I reported 5.46m (=2*2.73m) for a better skyview (GPS-norm) in http://www.vftt.org/forums/showthread.php?t=15025

Doug

 

[Kevin Rooney]

Interesting. Thanks for taking the time and posting the results, Doug.

 

[DougPaul]

Some additional info on the use of new lithium batteries:

The old 60CSx detects the overvoltage and shuts down immediately. The new 60CSx simply starts up normally. I only tested the start-up--I have no idea if there is any risk of damage to the (new) GPS with long-term use.

There is a note in the manual (Aug 2007, pg 2) warning against the use of lithium batteries because the initial voltage is too high. The changes in the new unit, however, may have been made since the last upgrade of the manual. A quick search of the Garmin website finds no new info on the topic.

Doug

 

[TomD]

I've got a 76CSx, which I understand is similar electronically to the 60CSx. No experience with lithium batteries, but I have used the Eneloop 2000 mah rechargeable batteries made by Sanyo, the same ones Doug has. Mine came in a kit with a charger and batteries, both AA and AAA. They work great. Never had them in super cold weather, but down to maybe +20.

I think the kit came from Costco. It is a little blue plastic box. I haven't bought batteries in years, except a few as backups. I've used the AAAs in my Princeton Tec headlamp.

My GPS book in the appendix says use lithium batteries below freezing but the only setting is for alkaline or NiMH, so no idea what the deal is. My book says "up to 18 hours" but I don't seem to have a batter saver setting, other than turning off the compass, which I read somewhere.

 

[DougPaul]

I've got a 76CSx, which I understand is similar electronically to the 60CSx.

They are reported to be the same electronics in a different cases. Someone with access to new and old versions might be able to determine whether the same upgrade as in the 60CSx has been applied to the 76CSx by performing tests similar to mine.

Never had them in super cold weather, but down to maybe +20.

I've used NiMHs down to ~10F without problems. Perhaps others can report usage at lower temps. (They are not as good in the cold as lithium primary (single-use) cells but are better than alkalines.)

I generally use NiMH's as the primary batteries in my headlamps, GPSes, and AA-powered cameras and carry lithiums as spares when hiking. If I want to minimize hiking weight, I'll use lithiums as my primaries.

Some devices can be damaged by the high initial voltage from fresh lithiums. Cannon does not list them for use in their AA-powered cameras and Petzl has issued a warning about using them in (at least some of) their headlamps.

Doug

 

[Gris]

?

'disrecommending...'

 

[DougPaul]

'disrecommending...'

After a quick bit of searching:
* The formal language geeks seem to think that it is not a word--they recommend "discommend".
* The search gets lots if hits on the word, so it is in use.

I worked professionally with language technology--real language is defined by usage, not by academics and high-school English (or whatever language) teachers. Once something receives some level of usage, it becomes part of the language.

So I was just ahead of my time...

(Besides, it got you to come out of the woodwork. Hi!)

Doug

 

[Kevin Rooney]

I've used NiMHs down to ~10F without problems. Perhaps others can report usage at lower temps. (They are not as good in the cold as lithium primary (single-use) cells but are better than alkalines.)

Doug

I've used NiMH's down to -25F, and they're OK for about 4 hours. Just bring at least 2 pairs of spares for a dayhike under those conditions.

 

[DougPaul]

I've used NiMH's down to -25F, and they're OK for about 4 hours. Just bring at least 2 pairs of spares for a dayhike under those conditions.

In what? Or what was the expected battery life at "normal" temps?

IIRC, I've read that NiMH are good to ~-20F, but I'm sure it depends on what you are trying to do with them. The cold slows the chemistry*, so I'd expect that lower current devices will operate at lower temps than higher current devices. (Of course, there is no hard and fast line--as the temp drops, the effective battery life decreases for a given device.)

* The cold doesn't remove energy from the battery--it just reduces the rate at which the battery can deliver the energy. A cold "newly dead" battery will come back to "life" when warmed up.

Another trick is to keep a spare set warm in your pocket and swap with the active set as needed. (Make sure they cannot form a short-circuit--you can get burned.) This is better for something that you use in short bursts rather than continuously.

Doug

 

[Kevin Rooney]

In what? Or what was the expected battery life at "normal" temps?
Doug

In my Garmin Vista GPS. My "normal" expected expected battery life was about 12 hours in warmer temps. I was using Kodak NiMH batteries.

I haven't used my Garmin 60CSx in as cold temps as often.

In really cold weather I keep the spare batteries, including the spare camera battery, in my pocket to help them stay as warm as possible.

Keeping devices out of the wind in very cold temps helps also as that slows convectional cooling.