tony chang's Blog

How to prolong lithium-based batteries

tony chang (deliton) — Thu, 04 Dec 2008 02:46:32 -0800

Battery research is focusing heavily on lithium chemistries, so much so that one could presume that all portable devices will be powered with lithium-ion batteries in the future. In many ways, lithium-ion is superior to nickel and lead-based chemistries and the applications for lithium-ion sony vgp-bps5 batteries are growing as a result.

Lithium-ion has not yet fully matured and is being improved continuously. New metal and chemical combinations are being tried every six months to increase energy density and prolong service life. The improvements in longevity after each change will not be known for a few years.

A lithium-ion battery provides 300-500 discharge/charge cycles. The battery prefers a partial rather than a full discharge. Frequent full discharges should be avoided when possible. Instead, charge the sony pcga-bp71 battery more often or use a larger battery. There is no concern of memory when applying unscheduled charges.

Although lithium-ion is memory-free in terms of performance deterioration, batteries with fuel gauges exhibit what engineers refer to as "digital memory". Here is the reason: Short discharges with subsequent recharges do not provide the periodic calibration needed to synchronize the fuel gauge with the battery's state-of-charge. A deliberate full discharge and recharge every 30 charges corrects this problem. Letting the sony pcga-bp2nx battery run down to the cut-off point in the equipment will do this. If ignored, the fuel gauge will become increasingly less accurate. (Read more in 'Choosing the right battery for portable computing', Part Two.)

Aging of lithium-ion is an issue that is often ignored. A lithium-ion battery in use typically lasts between 2-3 years. The capacity loss manifests itself in increased internal resistance caused by oxidation. Eventually, the cell resistance reaches a point where the pack can no longer deliver the stored energy although the battery may still have ample charge. For this reason, an aged sony pcga-bp2v battery can be kept longer in applications that draw low current as opposed to a function that demands heavy loads. Increasing internal resistance with cycle life and age is typical for cobalt-based lithium-ion, a system that is used for cell phones, cameras and laptops because of high energy density. The lower energy dense manganese-based lithium-ion, also known as spinel, maintains the internal resistance through its life but loses capacity due to chemical decompositions. Spinel is primarily used for power tools.

The speed by which lithium-ion ages is governed by temperature and state-of-charge. Figure 1 illustrates the capacity loss as a function of these two parameters.

MacBook Air Tests: Good Looks, Poor Battery Life

tony chang (deliton) — Fri, 28 Nov 2008 20:04:46 -0800

Ultraportable laptops have a history of requiring compromises when it comes to performance. Lately, the PC World Test Center has seen some improvements in this regard--especially with respect to battery life. Unfortunately, you'll still be making major compromises with the Apple MacBook Air a1078. In our tests, the Air produced respectable system performance, but mediocre battery life.

The Performance Numbers
When the PC World Test Center ran its tests using Apple's Boot Camp utility--which enables a Mac system to run Windows, too--the Air's WorldBench 6 score was 57. That score is just below the average WorldBench score of 59 for the field of 17 ultraportable notebooks we've tested recently for our Top 10 Ultraportables chart.

The MacBook Air's a1079 performance is more impressive, however, when you consider it against the nine ultraportable models we've tested with a minimum weight of four pounds or less (I selected this subset of data for comparison as these are the most likely competitive choices of someone considering a MacBook Air against its PC competition): There, the average WorldBench score is just 50.

The Sony VAIO VGN-TZ510N/B, the slimline PC notebook Steve Jobs compared MacBook Air m7318 to in his keynote, scored just 38 on our WorldBench 6 tests (the model we tested was running a 1.06-GHz Core 3 Duo U7500 CPU).

Only two models, the Asus W5Fe-2P025E and the Lenovo ThinkPad X61 bested the MacBook Air's final, post-Boot Camp WorldBench 6 score of 57. And, both the Asus and the Lenovo were running a faster processor than the MacBook Air: a 2-GHz Intel Core 2 Duo T7200. f

The MacBook Air runs a 1.6-GHz Intel Core 2 Duo processor (a 1.8-GHz processor is an option), and includes 2GB of memory, an 80GB 4200rpm hard drive, and a 13.3-inch display.

The only other model in our database that we've tested with a 1.6-GHz Core 2 Duo processor and 2GB of memory is the 4.5-pound Lenovo ThinkPad X61t; this model received a 64 on our WorldBench 6 tests compared with the Air's 61.

The Lenovo X61t has other specs that may have helped its performance vis-à-vis the MacBook Air: the X61t's 100GB hard drive spins at 5400rpm and its comparatively smaller display measures 12.1-inches on the diagonal.

Subpar Battery Life
In our tests, the Air's battery life averaged 2 hours, 31 minutes, which isn't even enough juice to cover the flight time from San Francisco to Dallas, let alone get a road warrior clear across the continent with a powered laptop.

The battery life performance of the Air also is quite dismal when we comparedt to the other nine laptops we tested in the four-pounds-and-under category. The MacBook Air's battery life was the third worst among those nine models (only the Everex StepNote SA2053T and Asus W5Fe-2P025E did worse). The average battery life score among these models was 4 hours, 37 minutes, and five models exceeded five hours in a1175 , a1185 battery life.

Running Boot Camp
The PC World's Test Center evaluation of the MacBook Air actually included running WorldBench 6 and battery life tests on the unit both before we installed the additional Boot Camp utility drivers the installation disc included with the MacBook Air, and after.

Without the Boot Camp utility drivers, we had to manually install some hardware drivers in Vista. Those drivers did not include some aspects of support for Apple's hardware; for example, the Air's function keys were inactive, and the keyboard wasn't backlit.  After we used the Boot Camp utility, the keys became active, and the keyboard became backlit.

The Air's performance before we installed all of the drivers and utilities from the Apple disc was actually slightly better: At that time, the MacBook Air received a WorldBench score of 61, and its battery lasted an average time of 2 hours, 53 minutes.

Vista Troubles, Too
The pre- and post-Boot Camp utility drivers' performance difference was significant enough for us to wonder what was going on. According to Apple, the Boot Camp utility installs drivers that are the necessary for enabling unique Mac hardware features, such as the MacBook Air's m8403 backlit keyboard, iSight webcam, trackpad (you get two-finger scrolling, but not the neat gesture maneuvers Air is capable of under Mac OS), and function keys (which enable hardware button controls for volume and display brightness, for example).

Meanwhile, we also noticed that Vista seemed to have some issues as well. We observed that, although you can bump down the display's brightness using the keyboard controls, our Vista installation on the MacBook Air showed incomplete power management options: The brightness control sliders and adaptive display functionality were missing in action.

According to Microsoft, the Windows Mobility Center controls in Vista checks to see if a system has a battery installed. If it does, then Vista assumes the system is a laptop, and enables the Mobility Center controls that provide power management options such as the brightness control sliders and adaptive display functions.

It's unclear why those controls were not enabled--especially considering that a battery is clearly represented in the Vista System Tray.

The MacBook Air's Limits m9324
While the MacBook Air clearly showed a performance advantage over other uber-lightweight notebooks, it's important to note that it is only an average performer once you consider it against the greater field of ultraportables.

More critically, its mediocre battery life should give serious pause to anyone who plans to use the Air on-the-go, and away from an outlet. If you buy one, stick close to electricity.

Computer Glasses for Computer Vision Syndrome Sufferers

tony chang (deliton) — Fri, 28 Nov 2008 20:01:01 -0800

The majority of people who suffer from the symptoms of Computer Vision Syndrome (CVS) - blurred vision, eyestrain and burning - are middle-aged and presbyopic. Presbiopia is the inability to focus at all distances with symptoms including squinting and headaches. So, getting computer glasses can transform the office environment for millions of workers at their workstations. As the glasses correct the intermediate zone of your vision, which is the typical distance (20-24") from your eye to the lcbtp03003 computer monitor screen, they enable the eye muscles to move from keyboard to monitor and back more easily. This alleviates the CVS symptoms of blurred vision and eyestrain. Perhaps you are sceptical of the need for specific computer glasses and consider them an unnecessary expense: less emphasis has traditionally been placed on acer btp-43d1 computer-induced vision problems than on the ergonomic layout of the workstation. Buying a pair of inexpensive, single-vision (intermediate) lenses off the rack might, then, seem a good idea. Unfortunately, as most people who need computer glasses also need their vision corrected in the near, and maybe far, zones as well, ready to wear, single-vision glasses don't usually fit the bill. Nor do cheaper, tinted glasses help presbyopic individuals. The pupil dilation, which results from reduced light entering the eye, can exacerbate the problem of blurred vision and eyestrain. Let's move now from the cheapest, ready to wear, the acer btp-58a1 computer glasses to affordable, but more expensive, eyewear with a greater degree of customization. Lenses can be selected to match the requirements of each eye. This gives you a pair of bifocal reading glasses with the upper area optimized for reading text on your monitor, and the bifocal area set to allow the correct focal distance for the keyboard and desktop. Customization of the individual eyeglass lenses, however, is sometimes not enough to prevent 'prism' which occurs when your eye movements are not perfectly synchronised. To overcome this problem, a choice of nose bridges is often made available which realigns the distance between pupils and removes this particular cause of eyestrain. These "do-it-yourself" computer glasses, which require you to find out your existing "add" prescription for each eye, are stylish and lightweight. They also come with anti-reflective coatings. Not only do these reduce the glare from ambient lighting in the workplace, which adversely affects the eye's ability to focus clearly on the monitor, but they also increase the scratch resistance of the lens. The best possible solution, of course, is btp-63d1 computer glasses made to match the requirements of your exact prescription and workplace setup. Fulfilling these requirements means a visit to your eye doctor and a willingness to pay more for your eyewear. Seeking professional help represents, for most people, the safest option. The more popular styles are the multifocals, particularly the progressive (no-line) lenses. These have a larger intermediate zone than normal progressives and allow you to see clearly in all zones (near, intermediate and far) at the same time while at work. However, in occupational progressive lens and lined trifocals, there is a trade-off between a larger intermediate zone and distance viewing. Both will allow you to see adequately in an office environment, but they are not suitable for wear outside the office. This problem of one pair of glasses for normal use and a dedicated pair for batcl50l computer use, can be obviated by the use of clip-ons. Provided you are fortunate enough to need two prescriptions only in your lenses (intermediate and near or intermediate and far). You can wear your regular prescription lens in the glasses and the computer lens in the clip. Finally, there is a question of tinted lenses in computer glasses. Opinions seem to vary on their use in reducing excessive "blue light" spectrum. As we have seen, an ultraviolet coating can filter out much of the blue light which reaches the eye from harsh fluorescent lighting. The jury seems to be out, though, when it comes to amber-tinted computer glasses. Many sportsmen use them to cut down glare from a bright sun, but, in the workplace, their use is not always thought to be beneficial. Some people believe the resulting cut in light transmission and the concomitant increase in use of the eyes focusing muscles, can aggrevate the very condition - eyestrain - which the tint is supposed to alleviate. Choose your computer glasses wisely, but if your blurred vision continues, look at your work habits and evaluate whether your working environment is ergonomically sound.