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Mutinousdoug
2006-08-06, 21:02
Had an annoying problem with my GPS last week on a 4 day hike Id like to relate for your edification and/or opinions.
I normally hike about 6 hours a day under my pack and 6-9 miles depending on terrain. This was to be about an 8 mile hike to Snowmass Lake up by Aspen Colorado; then back down the canyon to a side creek about 4 miles up to some lakes at 12,000 ft.
1st day was slowed down by a pretty good rain/hail storm starting about 4:00 pm that caused us to hole up at about 5 miles in. The rain on the ridge above us caused numerous rock and mud slides that we struggled with the 2nd day getting up to Snowmass Lake. What a mess. I should send a picture.

Day 3, I changed batteries in the GPS since the normal life in my unit with these NiMH AAs is about 12 hours, I put in fresh ones for the back track and detour up the side creek. When I put these in and turned the unit on it had a hard time acquiring satellites so, figuring it was because of the 2000 ft deep canyon we were in and the very wet forest we were in we took off figuring it would acquire eventually, when we got a little more into the open. Got down to the side creek, crossed the main creek and found a camp to stash our packs to climb up to the upper lakes, the GPS still only had a 2D fix on our site, but big deal, it knew where we were.
After hiking another 2-3 hours we stopped for a break and the GPS had turned itself off for lack of battery power. This was after only 5 hours of operation. I left my last spare set of batteries back at camp.
The hike and canyon we were in was such that it was unlikely we could have gotten lost but it might have been nice to keep our track when we were bushwhacking up one slope through the tag alders where there was no trail.
Anyway, long story short: next set of batteries worked fine from camp to the trailhead and on home in the car.
Do you think my trouble was from a poorly charged battery that was charged at the same time as my other 2 sets? Or from battery drain from not being able to fix satellites which I know does increase the load. I mark the batteries to keep them as sets and they are all about the same age and usage and charged on what is supposed to be a pretty good charger with a full charge indicator.
And lastly, if you are going to bring a battery powered device along with you; bring extra batteries. :damnmate:

Take-a-knee
2006-08-06, 22:25
I've never used NiMHydride batteries, I believe they are supposed to hold a longer charge than the old nicads, but I don't think they are up to par with the new alkalines. I wouldn't rely on them for a multiday trip. While hunting, I keep duracells in my Garmin Etrex and I have a pair of lithium AA's in my hunting pack. The lithium batteries have a ten-year shelf life, which means they are ideal for backup since they might still have some juice when you pull them out in a time of need. They are also lighter by a bit, if that is important to you, and they last a lot longer, though they cost a lot more. Even with the longer life they probably cost more to use, which is why I use the duracells unless I'm staying out for several days. I also hardly ever leave my GPS on for more than a few minutes at a time, if I'm changing azimuths I just stop and mark a new waypoint when I change directions. I rely on my map and compass and only use the GPS when I'm not sure of my location, much the same as using resection. In mountainous terrain, it would be wise to leave it on while going around really steep, dangerous terrain, where you need to retrace your exact trail, and trying to follow an azimuth at night could leave you on the edge of a cliff. I print my own maps with the National Geographic software using UTM coordinates. This makes it easy to figure out my location when I whip the Etrex out. This is also why I've never bought one of the newer wazoo models, all that stuff, especially the electronic compass, will drain the batts poste haste.

KLeth
2006-08-07, 01:38
Rechargeables have only a voltage of 1.2V where non-rechargeables are on 1.5V. My Garmin eTrex Venture drains rechargeables very fast, even faster when entering woods and/or under cloudy conditions where satelite ignal is weaker. I suspect that my GPS is designed for non-rechargeables and therefore requiring 1.5V but it can do with 1.2V but as soon as voltage drops (cold conditions) or additional power is needed it reports low-battery on even fresh rechargeables.
I've been looking at some very expensive non-rechargeable Lithium AA batteries but I've not tested them. Anybody have ?

Frolicking Dino
2006-08-07, 07:39
The male dino is shopping-impaired -- he just grabs the first set of batteries within his reach that are the right size paying no attention to type or price :stupido2:. He has lithium batteries in his hand-held electronic Bible and they have already lasted over twice as long as alkaline batteries normally do in this device.

KLeth
2006-08-07, 10:09
He has lithium batteries in his hand-held electronic Bible and they have already lasted over twice as long as alkaline batteries normally do in this device.
Well at the price I can buy them, they will need to last at least 5 times normal batteries . . . :smile: But it is temting just because of the weight.

Iceman
2006-08-07, 10:30
Lithium batteries rule! I have been using lithium batteries in all of my hiking and hunting gear. Lithium batteries last many many times longer than standard batteries. (I know, define "many many"...) Cost should not come into the equation when you are considering safety and weight. They last longer, work better in cold and weight less, what more could you want? Free? :biggrin:

blackdog
2006-08-07, 12:04
Once upon a time i was a R/C car racer. My radio wanted 8 x 1.5V alkaline batteries that got expensive after a while. But 8 x 1.2V wouldn't give me enough practice time on one charge. The radio transceiver wanted 12 volts and the only way to get there with NiMH batteries was by having ten of them wired together. In a strange electronics shop abroad i found a plastic holder for 12 AA-size batteries that i rewired and cut down to 10 slots. The holder was then put in a small packing sack (yes, with embroideries) that i kept inside my anorak (which also allowed me to practice longer in the autumn and to start earlier in the spring). Charging the ten cells was impossible with the stock charger, but to my suprise the R/C one had a mode for the transceiver accumulator that worked well. The bonus was one less charger to carry to the track.

There should be some way of using this system with GPS units too. If nothing else works then a switching voltage regulator IC should do the trick. If the handheld unit has four batteries then five NiMH cell work without the regulator. An electronics shop has the connector.

I would prefer rechargable cells instead of disposables. A third option would be to use the nanotube capacitors (http://www.sciencentral.com/articles/view.php3?article_id=218392803&cat=3_all) that recently have been created in laboratories. They can be packed with more juice than any rechargables on the market. (...and the racer in me wants them because of their high charging and discharging rates). PLEASE Remember that the nanotube capacitors i'm mentioning are still pretty much sci-fi for the general public, but it's an interesting development worth following IMHO.

toddhiker
2006-08-07, 13:46
Uhhh....Yeah.....What he said

Mutinousdoug
2006-08-07, 17:17
Rechargeables have only a voltage of 1.2V where non-rechargeables are on 1.5V. My Garmin eTrex Venture drains rechargeables very fast, even faster when entering woods and/or under cloudy conditions where satelite ignal is weaker. I suspect that my GPS is designed for non-rechargeables and therefore requiring 1.5V but it can do with 1.2V but as soon as voltage drops (cold conditions) or additional power is needed it reports low-battery on even fresh rechargeables.
I've been looking at some very expensive non-rechargeable Lithium AA batteries but I've not tested them. Anybody have ?

In my tests at home, freshly charged NiMH batteries with 2500mAh rating ran longer than alkalines in my Magellan Sportrak Topo, but I just turned it on and ran them until I got a low bat warning. I know that the NiMH lose a few % charge everyday after charging so they're not appropriate for extended trips with no recharge. So maybe the constant satillite search taxed the 1.25v batteries? I guess I could make a tinfoil hat for my GPS and do somemore tests to battery depletion.
I hate to use disposables but think I may be carrying one set of alkalines for backup in future.

Number7
2006-08-17, 03:15
Alkaline AA batteries only have about 700mah. That means a 2500mah Nimh will burn about 3 times longer. Power output from alkalines starts to drop off imidiately, and continually gets weaker, whereas nimh and nicads output is pretty flat and drops off very quickly at the end.

Alkaline's keep their charge in storage, nimh don't, that's why they are dead when you buy them.

Number7
2006-08-17, 03:22
www.batteryuniversity.com