SporkSports

I'm personally a big fan of the Sanyo and Powerex 2700's since I usually want longest life in my GPS & other high drain digital power devices. I have a bunch of Sanyo Eneloops too, but those are for the low-drain devices like remote controls, clocks, wireless mice, and so on. Those low-drain devices are the ones where you want the extremely low self-discharge. I wouldn't bother with the low discharge batteries in a high drain devices like a GPSr or especially digicam. You want high capacity for those and just make sure to charge up at least in the last couple weeks before you use the devices for the best runtime.

I purchased my 76S from them 5 years ago and have purchased various maps and accessories from them over the years. They're my favorite GPS store, I guess.

GPSr on an airplane is great for setting new records for the "max speed" in your unit. Highest I've gotten is just shy of 616 mph on a SWA B737 flying eastbound (constant tailwind), before they changed their policy to ban use of GPSr aboard aircraft.

You may laugh now, but Airbus really DID screw up the software on their first fly by wire jet. I forget which model, but they programmed the engine control wrong and ground radar incorrectly and the result was they had an aircraft fly right into the forest. There was a whole special about it on Discovery or something a few years ago; it was part of a government cover up in France since they didn't want to admit they totally botched the engine control, destroyed evidence, and so on. They say it was 100% pilot error and still have the pilot in jail to this day, if I remember correctly.

That is some of the best testing I've seen so far, but I do take issue with how it seems you declared a 1.38 mean voltage for NiMH cells. While a fully charged NiMH will have an initial output around 1.4 - 1.5v depending on load and temperature, it quickly drops in to the 1.15 - 1.2v range. Generally the best way to calculate the actual energy output of a NiMH is thus the amp rating times 1.2v. So a pair of 2.1 amp batteries would be (2 * 2.1 * 1.2) = 5.04 watt/hrs. So 5.04 / 0.214 = 23.5 hours expected runtime. With Alkalines, they have a pretty linear discharge rate, so 1.25v is supposed to be used as their median voltage.

Great results, looks like for two of the most common NiMH, the discharge ability is 85-90% as high around 35 degrees as it is at room temperature. In my view, that is still excellent performance. In a related note, I did a little research on lithiums and the most common one, the Energizer Lithium is rated at 2900mAh at 1.5 volts. If the true average voltage over its full discharge is 1.3 volts, then we can estimate they'll put out around 3.77 watt/hours of energy. Compare to a 2700 NiMH at 3.24 or 2000 NiMH at 2.4 watt/hours. If the lithium still holds effectively at 100% efficient at 35 degrees and the NiMH drops to 85%, then the NiMH drop to 2.75 and 2.0 watt/hours. Still respectable, IMHO, but it becomes clear lithium holds a substantial advantage at low temps. I'll still keep my NiMH, but if I was going somewhere without the ability to bring spare batteries, then I guess lithium is the way to go.

Weather isn't supposed to have any effect because of the wavelength that GPS is broadcast on. From http://www.gps.gov/ : "GPS provides accurate location and time information for an unlimited number of people in all weather, day and night, anywhere in the world."

I used to us my 76S whenever I'd fly. I always fly out of Phoenix, so I pretty much fly Southwest exclusively since they're the big airline for Phoenix and about 6 months ago they banned GPSr usage in flight. I don't know what their reasoning is, besides FUD. It's good to hear there's at least some carriers that still permit usage though.

Results are in; average between the 4 cells was 2333 mAh, or about 90% of what they deliver at room temperature. I'm actually very pleased with the result.

Bicycle geocaching. The GPSr sits up on the bars where it's wind-blasted with the outside air temperature, which in my parts is a relatively mild 50 degrees or so. Good enough that I get by with just long pants, a sweatshirt, and a warm beanie under my helmet to cover my head and ears, but cold enough to have problems with alkaline cells performing a lot worse than at 80+. I can do a good 2 hours or so like that, riding a caching along the way. I realize that not many people do that however, and the ones that do seem to be more partial to just using disposable lithium batteries instead, since they are well known as the top dog cold weather cells.

That's a great idea with the external antenna, now I kind of wish I had one. It's also good to hear data from another unit besides my 76S. I think the newer ones are supposed to have longer battery life, right? I just threw all my current findings online, here's a link: http://www.sporksports.com/brandon/2008-02...tery_test.shtml My longest duration in "normal" mode was 17 hours on the 2700's. I am still testing a set of Eneloops, although at a different temperature. Until the current temperature test is completed and/or your testing is done, I still won't know for sure how much of a difference the temperature makes in battery life. I may just end up re-doing my GPS testing from a window inside the house so I can have test data with all the samples being known at the same temperature.

Of course, the bummer there is that the unit can't have two maps active at the same time, so he'd have to disable the Topo maps for the driving portion, then disable the detailed road maps and re-enable the topo maps when doing the remaining portion on foot/bike.

I've done some searching around on here and so far the general consensus both here and on sources like Battery University is that the lower the temperature, the worse a battery's performance is. I know from my own experience that in my GPSmap 76S, Alkalines last barely even half as long at 50 degrees as they do at 80+ degrees. However, since I've pretty well abandoned Alkalines entirely now, I'm more interested in NiMH. So has anyone tested them before at cold temps? If not, well, feel free to put in your wager on how long my set of Powerex 2700's will last during a 200mAh discharge in a C-9000 in my refrigerator. Yes, it's a synthetic test, in that it's taking place in a discharge device and not an actual GPS unit, but only because I can't seem to get signal lock from within my fridge, nor can I maintain good temperature control of my back yard to generate completely repeatable results. So this particular set of batteries has about 7 sets of charge/discharge cycles on them and last reported capacity around 2550mAh per cell on average. They'll be due for a full recondition in a couple more cycles, but based on an approximate 2550mAh at 75 degrees, what does anyone think they either should (via scientific calculation) or might (based on personal experience) show as their capacity when they run out? Are there any tables showing temperature to deliverable power for the average NiMH out there?

Good point about measuring voltage, but the static voltage alone doesn't tell you how well it can deliver power unfortunately. Perfect example: Last night I went for a geocache find / bike ride at dusk and by about 1 hour into the ride it was too dark to read my GPS without the backlight. I had a set of alkalines in the unit (76S) that have maybe 3 hours of use on them. In the past, I'd observed at least 12 hours runtime in daylight in warm temps on Alkalines. Temp at this point was maybe 50 degrees farenheit. I switched on teh backlight and it immediately gave a low battery warning then the whole unit shut down about 10 seconds later. Needless to say, I was a little bummed out, since I don't have a speedometer on my bike other than the GPS unit, and I use the speed to help pace myself. Anyway, I've done three run-down tests with NiMH's in my 76S in 40 to 50 degree weather and it ranged from about 10 hours in normal receiver mode with the backlight on up to 22 hours in battery saver mode with no backlight. To have the unit cut out after 3 hours of no backlight just by turning on the backlight was a disappointment. This is my last set of AA alkalines that I own, but I'm still kind of tempted to buy another pack of 4 just to do run-down tests to share with the group. From what it seems, NiMH performs better at 40-50 degrees than alkalines, but further testing is needed to quantify the results.

Backups are always a good idea. The most secure is offsite storage of your data. If you have too much data to sign up for one of those internet-based backup services, you can also get a safe deposit box at your local bank branch and a pair of external hard drives. That's actually what I do. The external drives can be had for as little as $100 each and my safe deposit box is 3x10x15" and only $70/year. Quality backup software like True Image is $50. It's a fairly simple process really. I always have one external drive at the bank, then one at home to create a new backup. About once a week I do a full cold backup of the entire hard drive to the external drive, then drive or bike to the bank, and swap the old hard drive with the new one. Then I take the old hard drive home to make next week's backup copy. This way even if my house burns down, I still have a backup copy at the bank about 1.5 miles away. It doesn't protect the data in event of nuclear attack, but other natural disasters (hurricanes, tornados, floods) are extremely rare in Phoenix, so it's good enough for my purposes. Cheap, simple, and incredibly secure. I never have to worry about losing more than about 7 days of data at most now.

I would agree with the Vista HCx, or if the screen isn't large enough for your taste on the Vista, the 60/76 CSx would be my next pick.

MetroGuide was for GPS units like the GPSMAP 76 which did not have autoroute capability. Version 8 (which I think was 2006) was the last version published. It has since been discontinued, which sucks for us 76 owners, since now we can't get updated maps anymore.

Highlight the tracks you want to combine, then right click and select "Join the selected tracks".

I have a C-9000 and a total of some 36 or 40 NiMH batteries. I'm a bit of a techno-geek, so I love the flexibility that the C-9000 gives me, but it might be overkill for some. Also what I've noticed is that NiMH seems to perform better in the cold than Alkaline. I should do some empirical testing soon with Alkalines just to confirm it, but in my real-world testing, when outdoors at 50 degrees or so, my GPS map 76 won't even hold the backlight on after about 2 hours of use, as compared to my testing with the Powerex 2700's which went for just shy of 10 hours with the backlight in continuous use.