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Firmware in a battery
Smart batteries are used by Apple, Lenovo, HP/Compaq, and other companies.

Both you and the GP are correct. Li-ion batteries degrade over time no matter what, but they degrade least quickly when kept at 40% charge.

Here's a moderately technical explaination of failure modes in lithium and lithium-ion batteries. There are unexpected hazards; for example, charging a lithium-ion battery at very low temperatures can cause damage which will later cause a fire.

Notice the line in the article "Ebay from where I bought the battery haven't replied to the information I sent them." He bought a battery on Ebay? From whom? Who made this battery? Did it have UL approval? They put up an article on the battery explosion and didn't say that. Not useful.

Eh? Dan has written numerous articles on battery technology, I doubt even his worst foes will claim he doesn't have a basic understanding of it. You on the other hand... Or, if you prefer a more constructive approach, why not try some reading comprehension: "For best results, lithium ion batteries shouldn't be loaded to more than "1C". The C there stands for the capacity of the battery; the idea is that a 1000mAh-capacity battery shouldn't be asked to deliver more than 1000mA of current." That's the sentence before the one you quote. I didn't add the link, it's in the original, and it also contains helpful information on how to understand what the 1C refers to. You don't actually need it, though since...

although faster you are discharing the battery, the less actual energy they tend to provide.

See, that's what he - and the 3rd party site - are saying. The factor C is just a number indicating at what currents the battery draining starts to be efficient. Different chemistries have different values of C.

I certainly have only a basic understanding of battery technology, but it all seemed pretty clear in the review, and more so once I checked out the linked page.

The best you can generally get out of a battery is 5x it's capacity in discharge rate (5C), so a 2000mAH battery could be discharged at 10A.

To be exact, the best you can get out of a battery, if you don't care about heat or explosions, is the battery's voltage divided by the battery's internal resistance. :-)

A typical NiMH internal resistance would be, say, 778 mOhms. That means, for an AA NiMH battery outputting 1.25 volts, we have a maximum short current draw of 1.6 A. That's a lot of batteries to get what you want! :-)

1. powered by a built-in Li-polymer battery
2. Both players still feature only a USB 1.1 interface

The USB 1.1 isn't a deal breaker, but if i can't easily get to that li-polymer battery... It'd be the whole iPod story again. This time with an overseas manufacturer.

In general I agree that battery purchases should be delayed until you need them, but the availability of the battery must also be considered. Oftentimes, new batteries will no longer be available from the manufacturer if you wait five years to buy one.

I've opened all the side panels and bottom panels and none of them leads to a hard drive. As best I can tell, the hard drive is near the front of the laptop under the touchpad, but I haven't been able to access it yet, even after unscrewing all the screws on the case and opening the laptop as far as I dared.

If you know how to replace the hard drive on a compaq presario 2100us, I'd love to hear from you.

As for the question of whether to leave the battery in, I usually take it out for long term storage because the buchmann battery faq says li-ion batteries store best at 40% charge level and cold temperatures. While I don't go so far as to refrigerate my batteries, I can't help but think that storing them at 40% charge, 25 degC is better than storing them in my laptop where they would be at 100% charge, 40 degC. So far my oldest battery (1 year old) is at about 88% of original charge, which is in line with the figures given on the web page considering that it has seen more usage than just sitting in storage.

They're "venting with flame". (Kudos for the link to the site go to Steve Cowan)

They're "venting with flame". (Kudos for the link to the site go to Steve Cowan)

Where I work I need to know a lot about rechargeable batteries. My impression of Li-ion / Li-Polymer is that they don't mind having a "float charge" at all... what the previous posts fail to mention is that for safety reasons, all Li-based chargers are intelligent enough to not overcharge the batteries (except cheap offshore chargers and car adapters, but you won't likely find anything like that for your ipod). In other words, I believe it is safe to leave an ipod plugged in indefinitely.

We picked up a battery analyzer from Cadex, which is really cool, and I use it every day.

But the really cool thing is that the charger came with a little paperback book called "Batteries in a Portable World", which offers a lot of insight into varying battery chemistries, even though it is sort of a pitch for Cadex products.

Nevertheless there is an online version of this book. Go to chapter 2 and read up! There is some very valuable battery maintenance info in there -- if you own a single rechargeable battery it is a very good read. (The website asks for your email address, but you can probably just use a fake one).

I think the consensus is Li Ion and NiMH batteries are better kept close to full charge, and NiCads should be drained fully before recharging.

iPods use a Li-Ion battery.

It doesn't draw too much power, it's just too cute to bulk itself up with a battery compartment. The lithium polymer design is squishy and can squeeze in almost anywhere. If they'd made it run on AA's like everything else in the world, it wouldn't have looked the same.

The iPod idea sucks, and I've avoided buying one because of it. You mean when it's drained, I have to plug it in for several hours? I can't just swap in some charged batteries and keep going? Screw that!

The AA is the dominant power standard and will remain so for the forseeable future. Most of my gear runs from AA's and I like it that way. I keep a charger and a spare set in my car, and I'm never without power. This includes my camera, GPS unit, radios, flashlights, and other stuff. I wouldn't have it any other way.

Cell phone makers should be shot for not building their products around AA's like every other portable device in the world. Sure, they make extra money from selling batteries, and the markup on them is astronomical. I'd gladly pay extra for a phone if it used the same AA's that I already run my life on, because it's not about money, it's about versatility. Wouldn't it be nice to be able to swap in a new pair and keep going?

I wish there were a good solution for laptops. They draw too much power for NiMh AA cells, I mean do you really want to plunk 20 of them into the compartment? The 18650 lithium-ion cell is overwhelmingly standard in the industry, and if you look at a dozen different laptop batteries you can see how they're all designed around the same size of cylindrical cell. Because lithium is so touchy though, they must always be kept behind a protection circuit. There's an excellent book called Batteries in a Portable World that goes into a lot detail. (it's free online after giving your email addy)

It'd still be nice to see standard batteries for laptops. Again, I'd pay extra for a laptop if I knew there'd always be abundant replacements for it instead of having to hunt down the exact replacement several years later. Ideas?

Batteries suck. I can't wait for Mr. Fusion!

So, for somebody like me, 500 charges lasts nearly a decade (assuming the battery doesn't crap out before that due to old age.)

Li-Ion batteries will die due to old age in much less than a decade! Here's a great resource which explains. It's sponsored by a company that produces battery chargers.

I have taken an interest in the topic, having had a number of (expensive) Li-Ion batteries die on me in the past five or six years.

On another (somewhat related) topic, it sucks that no one will sell you li-ion cells... I pried apart one of the old battery packs on a Thinkpad and googled the Panasonic cell part number - and the company I tried to buy from required extremely detailed specifications of what I was going to do before they would sell to me. (Their agreement with Panasonic requires them to "qualify" all orders before sending quotes.)

Right. I imagine that the battery itself wasn't the entire problem, anyway. Most likely the guy didn't take care of how he was treating it. Lithium Ion are the best batteries in my opinion, but they still can be damaged by overheating or overcharging, as well as random failure.

Dan's Data had a link to this site not long ago about it.

1. My iPod also had the battery die early and out of warranty
2. I contacted Apple far before the $99 replacement offer
3. Apple replaced the battery. In short, I just plain don't believe the Neistat's story. Yes I've known people whose battery has died, and NONE of us have been told to get a new iPod. We had them replaced, by apple, for substantially less than the cost of a new iPod. I suspect the Neistat's are either lying or attempting to take advantage of an utterly atypical customer experience for a bit of showmanship. Apple's customer service has made me all the more likely to buy a mac, and soon.

Read about the Neistat brother's refusal to point out Apple's true replacement policy until they had no other choice. Finally after more than a month the link is there to Apple's replacement program. Their site wasn't about information, it was about being drama queens.

In any case, whatever you believe or don't about batteries and how long they should/shouldn't last, all battery tech is a tradeoff between weight, size, capacity, cycle life, total life, storage life, charge time, etc.

Read Batteries in a portable world with some simple explanations of the chemistry in batteries. After seeing some of the crap about battery life thrown about here, it's eye opening to read the truth.

Since when do LI-Ion batteries DIE? Since when?

Since always. Li-ion batteries often show failure at 2 years.

Li-ion

"Aging is a concern with most Li-ion batteries. For unknown reasons, battery manufacturers are silent about this issue. Some capacity deterioration is noticeable after one year, whether the battery is in use or not. Over two or perhaps three years, the battery frequently fails."

Apple's engineers sat down one day, desinged the cheapest battery in the world that barely met all the requirements, and laughed as they increased Job's profit margin and screwed the end user with an inferior product.

I don't think Apple is designing batteries. Like every other box vendor they are buying technologies available from others.

According to this article the mobile phone companies prefer "venting with flame".

Coincidently I was looking at this stuff a couple of days ago. My Nokia 8250 had started turning itself off when in use. I wasn't sure whether it was the battery dying or the phone so I went to borrow a spare battery to test with.

When I opened the phone I noticed that rather than being flat the battery was bulging out as if it was pregnant. The bulge was enough that it was difficult to get the battery cover back on.

I now have a whole new phone (another Nokia, a 7250i).

One thing I've heard is that lower amp-hour batteries are actually BETTER in some applications. In increasing the electrode surface area that goes into a battery, manufacturers encounter a tradeoff with reliability, internal resistance, and longevity.

A lower capacity cell will have thicker electrodes, which conduct more easily and will last through more charge/discharge cycles. Ideal for applications like camera-flash units that draw very heavy current. You'll just have to charge them more frequently.

The higher-capacity cells would be more suitable for low-drain devices, like portable music players, or cameras that don't see much flash use. Their higher internal resistance doesn't pose a problem when the power draw is low.

Another thing to be aware of is that many chargers go into a blitz charging mode on startup, blasting heavy current into the batteries for the first hour, before backing off, taking a reading, and determining how much further charging is needed. This makes sense if the charger is plugged in constantly, and only drained batteries are tossed into it. It only becomes a problem in situations like mine: I was running a little 4xAA charger from the inverter in my vehicle, which would cycle on and off with the engine. Leaving batteries in the charger would cause them to get blasted every time I turned the car on, shortening their life dramatically. Don't do that. Now before I shut off the engine, I peek at the charger to see if it says they're charged. If so, I take them out and toss 'em in a cupholder, so they don't have to endure further charging. Keeping a spare set in my vehicle has proven indispensable though.

Avoid Rayovac. I got a Rayovac "3 in 1" desktop charger, which advertises the ability to charge NiCd, NMH, and rechargeable alkalines. Then I threw in a set of four Rayovac NMH AA's. A few hours later, I discovered that they'd gotten so hot during charging, their labels had warped and peeled, exposing the bare metal can underneath. They still work fine, holding plenty of charge to be useful, but the bare metal means I can't use them in certain devices' battery compartments because of shorting concerns. I put a set of ancient Radio Shack NiCd's in it, and it cooked them too. They were probably dead anyway, but the point is, the Rayovac charger doesn't have a thermal cutoff, which it should! Curiously, this charger works just fine on my other batteries, even AAA's never get more than warm during charging.

Ironically enough, another set of Radio Shack "high capacity" NiCd AA's from the same era work just fine, in the Rayovac charger and others. Because the NiCd chemistry has a lower self-discharge than NMH, they're ideal for occasional-use standby duty. Those old cells sit in my Mag Lite.

Really, for standby jobs, the best chemistry is rechargeable Alkaline. They have almost no self-discharge, so they can sit for months on end and still be ready for service. I've got a pair of Renewal AAA's in my laser pointer, I think I've charged them 5 times in the 5 years I've owned them. (BTW, it's worth the extra bucks for a laser that takes standard batteries. After you've replaced those button cells 2 or 3 times, you begin to see why.)

You should check out Isidor Buchmann's excellent book on the subject. After a free "who are you?" registration, you can read the whole thing on line.

P.S. Anyone know an outfit that rebuilds Lithium-ion laptop batteries?

The mention of NiMH on a battery pack does not automatically guarantee high energy density. A prismatic NiMH battery for a mobile phone, for example, is made for slim geometry and may only have an energy density of 60Wh/kg. The cycle count for this battery would be limited to around 300. In comparison, a cylindrical NiMH offers energy densities of 80Wh/kg and higher. Still, the cycle count of this battery will be moderate to low. High durability NiMH batteries, which are intended for industrial use and the electric vehicle enduring 1000 discharges to 80 percent depth-of discharge, are packaged in large cylindrical cells. The energy density on these cells is a modest 70Wh/kg.

The mention of NiMH on a battery pack does not automatically guarantee high energy density. A prismatic NiMH battery for a mobile phone, for example, is made for slim geometry and may only have an energy density of 60Wh/kg. The cycle count for this battery would be limited to around 300. In comparison, a cylindrical NiMH offers energy densities of 80Wh/kg and higher. Still, the cycle count of this battery will be moderate to low. High durability NiMH batteries, which are intended for industrial use and the electric vehicle enduring 1000 discharges to 80 percent depth-of discharge, are packaged in large cylindrical cells. The energy density on these cells is a modest 70Wh/kg.

just picked one of these up the other day. got 2.4.20 w/ apm in kernel running on it. set up a script to monitor its power consumption, and just let it sit for most of a day. discharged normally from 96% to 37%, then dropped to 5% over the course of 1 minute and ticked down to 1% before i shut it down and recharged it. so, the first theory was, well, its a 6 cell pack, perhaps 2 of the cells are going bad (resulting in ~32% or 1/3 of the 'available' charge going away), but since then, i've used it 2 more times, where i've run it down quite a bit, and the 'big drop' point seems to be getting lower (aka last time i checked, it went from 34% to 5%, which isn't great, but if the trend continues, the battery will seem to 'recover').
time to karma whore:
Another Thinkpad 600 users' battery stories
excerpts from the linux mailing list about the problem
and another users overview of the battery problem on the thinkpad 600
apmiser which you can get with tpctl will help your batteries last longer while you're on the road (note: you'll need APM support in the kernel to use'em)
Tips for better life out of LiIon batteries

Becaue the rechargeable Lithium cells have a nominal voltage of 3.6 volts, where the AA/AAA batteries have a nominal voltage of 1.2 - 1.25 volts. Take a look here for more details.

I used to think this would be a great idea, too. I mean, since Li-Ion and Li-Polymer batteries have a higher gravimetric and volumetric energy density (wH/kg and wH/liter, respectively) than any other technology, they'd make great replacements for the AA/AAA batteries we go through. Unfortunately, not all AA/AAA consuming devices can use voltage in increments of 3.6 volts.