Rechargeable Lithium Ion Batteries

[+user13371]

Seeing more than one GPS thread get highjacked by arguments about the evils of rechargeable Li-Ion rechargeable batteries, I figured this subject needed its own place.

 

The DeLorme Blue Logger comes with a Li-Ion rechargeable battery, with a good design:

 

- The battery is removable/replaceable. It's a rectangle about 1-/38" by 2-3/4" a about 1/8" thick. Rated at 3.7v, 900 mAH. Fully charged, the battery will run the unit for around 14 hours.

 

- A replacement or spare battery from DeLorme costs around $30. A comparable battery may be available elsewhere but I haven't looked.

 

- The Blue Logger comes with both an AC adapter and a 12V auto adapter. Either adapter can plug directly in to the the Blue Logger, or into a "charging cradle" also provided.

 

- The charging cradle has not only a place to put the Blue Logger, but also a slot for charging a spare battery.

 

SO... It's not like a sealed gadget that needs factory service when the battery ultimately fails. And if you'll be roughing it for an extended period of time, you can carry a spare battery. Or LOTS of spares, as they're smaller/lighter than a pair of AA or AAA cells).

[+embra]

I;m not adding anything new to the discussion by stating the obvious:

Lots of spares X $30 each = Lots and Lots of money.

 

Other than that, I think I can live with the pros and cons of Li-Ion in an implementation like you describe. It just seems to me like NiMH works so well (especially now that they are getting batts up to 2300 mAH or more) that it's not a good marketing move. The market may prove me wrong.

 

I've gathered from other threads that cell phones are dominated by Li-Ion because of the need for custom sizes to fit in the very small spaces. Can anyone confirm my impression that we *don't * see Li-Ion replacing standard AA's in, say, digital cameras because there's more room to accommodate their size? (I don't know enough of the digital camera market to make any authoritative statements...I see that our inexpensive cameras take AA's, but my wife's high-end Nikon and, before that, Canon, take Li-Ion.)

[peter]

In my view a much better design would have been to use a Li+ rechargeable in the RCR-V3 form factor. It's a 3V cell in about the shape of a pair of AA cells lying side-by-side, so the same battery compartment that holds it can alternatively hold a pair of AA alkalines (or NiMHs). Gives you the weight and 'charging inside the unit' advantages of other Li+ cells, but also lets you substitute readily available AA cells whenever it may be needed.

 

$30 for a spare cell is better than most, but it's still much more expensive than non-proprietary designs like a pair of NiMH AA cells. And it's still a unique cell type just for that device, so I can't decide to switch cells from my camera into my GPS when needing to find my way, or from my GPS into my flashlight when I just need a few minutes of light to find the campground restroom.

 

Yes, the proprietary form factors make sense if you really need to get the smallest physical size possible - and that seems to drive much of the cellular market. But our GPS receivers aren't generally all that tiny anyway (nor would I want them to be since I'd like a reasonable screen size), and ironically, the units that are the most compact (Gekos, eTrex, eMap, iFinder) run on standard AA and AAA cells.

[+NightPilot]

As long as the unit is otherwise reliable, and the size is acceptable, I think using AA batteries makes a lot of sense, because they're so widely used and available. Most electronic devices these days use AA batteries - I use them in my GPS, a couple of flashlights, CD player, radio, and on and on. I can buy a bunch of NiMH batteries, and mix and match at will. No matter what goes dead, I have fresh batteries for it. If everything used unique batteries, then it gets to be a problem, because I have to plug everything in for charging, and I don't have that many outlets in the truck. I have an inverter, but I don't want to have to plug everything into it. One of the things that made the modern world work as well as it does was standardization - the ability to take a part and put it into any device, not just one specific device. It started with guns, moved to cars, and to everything else. I think this also applies to batteries - my preference is for everything to use the same batteries, so it's easy to change them. Palm tried this, but ran into problems with reliability, since the capacitor that maintains the charge to retain memory while the batteries are replaced isn't reliable enough, and all memory was lost every time the batteries were changed. That and the higher energy density of LiIon batteries dictated a change, but for most devices the energy density isn't an overriding factor. NiMH AA batteries will last long enough in most devices.

 

I think peter's observation is very valid. Using the 2-AA form factor allows regular AA batteries to be used if desired, or in an emergency, and still gives the energy density when that's important. Of course, this isn't always possible, because for some applications size matters, and bigger isn't better.

Edited February 6, 2005 by NightPilot

[+user13371]

In my view a much better design would have been to use a Li+ rechargeable in the RCR-V3 form factor.

If you've got a gadget big enough for it, that might be a good choice. But there's another design consideration with that battery. To be able to charge it in the unit (as opposed to taking it out for charging in a separate device), you have to design the gadget to sense what kind of battery is installed - RCR-V3, or a non-rechargable CR3, or a pair of AAs.

 

... the proprietary form factors make sense if you really need to get the smallest physical size possible - and that seems to drive much of the cellular market.  But our GPS receivers aren't generally all that tiny anyway...

As far as the Blue Logger goes, size certainly drove the battery choice. Smaller than most cell phones, weighs under 3 ounces. AA (or even AAA) batteries would have meant a larger and heavier gadget.

 

$30 for a spare cell is better than most, but it's still much more expensive than non-proprietary designs like a pair of NiMH AA cells.

With an expected lifetime of 300 to 500 charging cycles, that could add as much as 10 cents a day to the cost of using the unit -- assuming you run it down completely every day and never power it from the charger in your car or anything like that. But I don't think that's a realistic usage pattern. I expect most users would get two or three years out of the original battery, bringing the battery cost down well under 5 cents a day.

 

Of course, the only users who will buy a spare battery are the ones using the device continuously for long periods away from a power source -- or those who keep it for a few years without upgrading (eventually do wear the original battery out). That may be a small portion of DeLorme's intended market for this device.

 

And it's still a unique cell type just for that device, so I can't decide to switch cells from my camera into my GPS when needing to find my way, or from my GPS into my flashlight when I just need a few minutes of light to find the campground restroom.

All right, I just gotta ask this: You carry more than one gadget that runs on AA or similar, and you don't carry spares, and in a pinch you rely on swapping batteries between devices? Does this happen a lot? Or EVER?

[+NightPilot]

Whether it happens or not, having devices that use a common battery makes life much easier, because you can carry one set of spares that will go into whatever needs fresh batteries. It's a little difficult to carry an AC charger around while walking. The Bluelogger is fine for in car use, but for extended hiking trips it won't do the job. Horses for courses.

[peter]

But there's another design consideration with that battery.  To be able to charge it in the unit (as opposed to taking it out for charging in a separate device), you have to design the gadget to sense what kind of battery is installed - RCR-V3, or a non-rechargable CR3, or a pair of AAs.

Sure, but that circuitry is a standard part of many devices designed to use RCR-V3 batteries, like digital cameras, and probably costs no more than a few cents per unit in manufacturer quantities. Similar to the circuitry to detect the film speed of different 35 mm film cartidges that's built into many very inexpensive cameras.

 

As far as the Blue Logger goes, size certainly drove the battery choice.  Smaller than most cell phones, weighs under 3 ounces.  AA (or even AAA) batteries would have meant a larger and heavier gadget.

Maybe I'm not seeing all the possible applications of the Blue Logger, but frankly it's not clear to me how it would hurt if it were an ounce or so heavier and slightly larger. In the case of cellphones, there are lots of competing models and a significant portion of the market views the smallest phone as a status symbol, so there's a huge incentive for the manufacturer to come out with a small "sexy-looking" model.

 

$30 for a spare cell is better than most, but it's still much more expensive than non-proprietary designs like a pair of NiMH AA cells.

With an expected lifetime of 300 to 500 charging cycles, that could add as much as 10 cents a day to the cost of using the unit -- assuming you run it down completely every day and never power it from the charger in your car or anything like that. But I don't think that's a realistic usage pattern. I expect most users would get two or three years out of the original battery, bringing the battery cost down well under 5 cents a day.

The point was not the cost per day of use, but the cost of carrying spares. If I have 6 or 7 gadgets that each need a unique battery, then I have to carry about $200 worth of spares on a trip even when the likelihood of needing them is rather small. In my experience, rechargeable cells can fail suddenly well before the end of their normal life expectancy, so if I don't want to risk having one or more of these devices be worthless on the trip I need to carry at least one spare cell per device. Furthermore the spare cells deteriorate even when not used, so much of the cost will end up being wasted - not to mention the added weight and inconvenience of carrying multiple types of spare cells instead of just a few standard NiMH AAs. And on many trips the need to carry spare cells is much greater with the proprietary designs since you can't expect to find them at any convenience store along the way like you can AA cells.

 

Of course, the only users who will buy a spare battery are the ones using the device continuously for long periods away from a power source ....  That may be a small portion of DeLorme's intended market for this device.

 

If you don't plan to run it for an extended period away from a power source, why bother with a design that uses a high capacity internal battery at all?

 

All right, I just gotta ask this: You carry more than one gadget that runs on AA or similar, and you don't carry spares, and in a pinch you rely on swapping batteries between devices?  Does this happen a lot?  Or EVER?

 

I never said that I didn't carry spare NiMH cells. I generally carry as many as I think I'll need on a trip. But the interchangeability between devices cuts down on the number of spare cells required. Only if I run out do I resort to swapping cells between devices. I believe that happened three times this past year. A couple times I took cells from the camera to operate the GPS for an extra day and once I briefly took cells from the GPS to take a couple more pictures.

[+Rubberhead]

I really like the idea of AA batteries whether standard alkaline, NiMH, or the newer titanium or lithums.

 

I really like being able to pop-in a set of titaniums or lithums if the weather gets really cold.

[+Searching_ut]

Disregarding all other factors, just look at the cost’s: The battery you describe provides 14 hours of usage and can probably be recharged in about 2 hours. Should you need to carry spares, they of course will cost $30 each, take two hours each to charge, and will most likely need to be charged in your device meaning you have to have at least 2 hours times the number of batteries desired available at some time prior to needing the batteries. If you look on the shelf at Wal-Mart, you’ll find the current crop of Eveready AAA batteries are rated at 850 Mah, and the AA’s are rated 2500 Mah. They cost around $10 for 4, and can be charged in about 15 minutes using a charger that costs about $25. With these, you have to allow time to recharge closer to the time of use as they don’t hold a charge while stored as well as Lithiums do. (They discharge about twice as fast) You can however charge multiple batteries during the same 15 minutes. Remember also, that with both types of battery, storing them fully charged isn’t good as it shortens the life of the battery. Given the energy available in the Eveready batteries, you should expect to be able to run your unit for about 9 hours with the AAA batteries, and 24 hours with the AA’s. Is the size difference really worth the cost and recharge time differences to you? Do you really want to have different types of batteries in all of your electronic devices with the resulting need for numerous different types of expensive spare batteries? How long do you intend to keep your electronic device? Will replacement batteries be available in couple years when your current batteries die out, or will the device be orphaned? (Neither Lithium or NiMh batteries have great shelf lifes, but you can expect the standard form factors to be available in the future making replacement of AA or AAA less of an issue pluse, with standard form factor batteries, you always have the option of using expendable batteries if and when needed.)

 

My own thoughts are that proprietary batteries are becoming way to expensive and eating up much more of my personal budget than I would like. Even though I try to avoid proprietary batteries when possible, I find I have a ridiculously large amount of money tied up in proprietary batteries in situations where there is no real benefit when compared to using a standard form factor battery. As for the arguments on whether NiMh or Lithium technology is better, the hype for both tends to greatly exceed the ability for the batteries to deliver. In addition, the technology and formulations have been changing so fast as to make it impossible to predict real world reliability or life expectancy for the latest generations of both types.