Resource: Some Info About Batteries

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sg219
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Resource: Some Info About Batteries

Post by sg219 » Sat Nov 20, 2004 12:57 am

I was wondering around the internet and found some good info on batteries that was pretty straight forward and complete.


Types of Batteries

Nickel Cadmium (Ni-Cd)
Nickel Cadmium (Ni-Cd) batteries were the standard technology for years, but today they are out of date and new laptops don't use them anymore. They are heavy and very prone to the "memory effect". When recharging a NiCd battery that has not been fully discharged, it "remembers" the old charge and continues there the next time you use it. The memory effect is caused by crystallization of the battery's substances and can permanently reduce your battery's lifetime, even make it useless. To avoid it, you should completely discharge the battery and then fully recharge it again at least once every few weeks. As this battery contains cadmium, a toxic material, it should always be recycled or disposed of properly.

NiCad batteries, and to a some degree NiMH batteries, suffer from what's called the memory effect. Memory Effect means that if a battery is repeatedly only partially discharged before recharging, the battery will forget that it can further discharge. The best way to prevent this situation is to fully charge and discharge your battery on a regular basis.

Nickel Metal Hydride (Ni-MH)
Nickel Metal Hydride (Ni-MH) batteries are the cadmium-free replacement for NiCad. They are less affected by the memory effect than NiCd and thus require less maintenance and conditioning. However, they have problems at very high or low room temperatures. And even though they use less hazardous materials (i.e., they do not contain heavy metals), they cannot be fully recycled yet. Another main difference between NiCad and NiMH is that NiMH battery offers higher energy density than NiCads. In other words, the capacity of a NiMH is approximately twice the capacity of its NiCad counterpart. What this means for you is increased run-time from the battery with no additional bulk or weight.

Lithium Ion (Li-ion)
Lithium Ion (Li-ion) are the new standard for portable power. Li-ion batteries produce the same energy as NiMH but weighs approximately 20%-35% less. They do not suffer from the memory effect unlike their NiMH and Ni-Cd counterparts. Their substances are non-hazardous to the 0. Because lithium ignites very easily, they require special handling. Unfortunately, few consumer recycling programs have been established for Li-ion batteries at this point in time.

Smart Batteries
Smart batteries are not really a different type of battery, but they do deserve special mention. Smart batteries have internal circuit boards with chips which allow them to communicate with the laptop and monitor battery performance, output voltage and temperature. Smart batteries will generally run 15% longer due to their increased efficiency and also give the computer much more accurate "fuel gauge" capabilities to determine how much battery run time is left before the next recharge is required.

General Battery Care
Even if the battery case looks the same, you cannot just upgrade to another battery technology unless your laptop has been pre-configured from the manufacturer to accept more than one type of battery type, since the recharging process is different for each of the three types of batteries.

A battery that is not used for a long time will slowly discharge itself. Even with the best of care, a battery needs to be replaced after 500 to 1000 recharges. But still it is not recommended to run a laptop without the battery while on ac power -- the battery often serves as a big capacitor to protect against voltage peaks from your ac outlet.

As the manufacturers change the shapes of their batteries every few months, you might have problems to find a new battery for your laptop in a few years from now. This is somewhat of a concern only if you anticipate using the same laptop several years from now. If in doubt, buy a spare battery now - before it's out of stock.

New batteries come in a discharged condition and must be fully charged before use. It is recommended that you fully charge and discharge the new battery two to four times to allow it to reach its maximum rated capacity. It is generally recommend that you perform an overnight charge (approximately twelve hours) for this. Note: It is normal for a battery to become warm to the touch during charging and discharging. When charging the battery for the first time, the device may indicate that charging is complete after just 10 or 15 minutes. This is a normal with rechargeable batteries. New batteries are hard for the device to charge; they have never been fully charged and are not broken in. Sometimes the device's charger will stop charging a new battery before it is fully charged. If this happens, remove the battery from the device and then reinsert it. The charge cycle should begin again. This may happen several times during the first battery charge. Don't worry; it's perfectly normal. Keep the battery healthy by fully charging and then fully discharging it at least once every two to three weeks. Exceptions to the rule are Li-Ion batteries which do not suffer from the memory effect.

Batteries should be stored in a discharged state since they can self-discharge and may become inactive after a long storage period. They should not be stored for any length of time while connected to the laptop. High humidity and temperatures can cause the battery to deteriorate, so these should be avoided during storage.

Do not remove and carry a battery pack in your pocket, purse, or other container where metal objects (such as car keys or paper clips) could short-circuit the battery terminals. The resulting excessive current flow can cause extremely high temperatures and may result in damage to the battery pack or cause fire or burns.






The Lithium-Polymer Battery:
The phrase "lithium-polymer" has become synonymous with advanced battery technology. But what is the relationship between "polymer" and the classic lithium-ion battery? In this article we examine the basic differences between the lithium-ion and lithium-ion polymer battery. We look at packaging techniques and evaluate the cost-to-energy ratio of these batteries.
The lithium-polymer battery differs from other battery systems in the type of electrolyte used. The original design, which dates back to the 1970s, uses a polymer electrolyte. This electrolyte resembles a plastic-like film that does not conduct electricity, but allows the exchange of ions (electrically charged atoms or groups of atoms). The polymer electrolyte replaces the traditional porous separator, which is soaked with electrolytes.

The dry polymer design offers simplifications with respect to fabrication, ruggedness, safety and thin-profile. There is no danger of flammability because no liquid or gelled electrolyte is used.

With a cell thickness measuring as little as 1mm (0.039in), design engineers are left to their own imagination in terms of form, shape and size. Theoretically, it is possible to create designs that form part of a protective housing, are in the shape of a mat that can be rolled up, or are even embedded into a carrying case or a piece of clothing. Such innovative batteries are still a few years away, especially for the commercial market.

Unfortunately, the dry lithium-polymer suffers from poor conductivity. The internal resistance is too high and cannot deliver the current bursts needed for modern communication devices and spinning up the hard drives of mobile computing equipment, although heating the cell to 60 degrees C (140 degrees F) and higher increases the conductivity to acceptable levels. This requirement, however, is unsuitable for portable applications.

Some dry solid lithium-polymers are currently used in hot climates as standby batteries for stationary applications. One manufacturer has added heating elements in the cells that keep the battery in the conductive temperature range at all times. Such a battery performs well for the application intended because high ambient temperatures do not degrade the service life of this battery in the same way as it does with the VRLA type. Although longer lasting, the cost of the lithium-polymer battery is high.

Engineers are continuing to develop a dry solid lithium-polymer battery that performs at room temperature. A dry solid lithium-polymer version is anticipated by 2005. This battery should be very stable, would run 1,000 full cycles and would have higher energy densities than today's lithium-ion battery.

How then is the current lithium-polymer battery made conductive at ambient temperatures? Most of the commercial lithium-polymer batteries or mobile phones are a hybrid. Some gelled electrolyte has been added to the dry polymer. The correct term for this system is "lithium-ion polymer". For marketing reasons, most battery manufacturers call it simply "lithium-polymer". Since the hybrid lithium-polymer is the only functioning polymer battery for portable use today, we will focus on this chemistry variation, but use the correct term of "lithium-ion polymer".

With gelled electrolyte added, what then is the difference between lithium-ion and lithium-ion polymer? Although the characteristics and performance of the two systems are very similar, the lithium-ion polymer is unique in that the solid electrolyte replaces the porous separator. The gelled electrolyte is simply added to enhance ion conductivity.

Technical difficulties and delays in volume manufacturing have deferred the introduction of the lithium-ion polymer battery. In addition, the promised superiority of the lithium-ion polymer has not yet been realized. No improvements in capacity gains are achieved - in fact, the capacity is slightly less than that of the standard lithium-ion battery. For the present, there is no cost advantage in using the lithium-ion polymer battery. The major reason for switching to the lithium-ion polymer is form factor. It allows wafer-thin geometries, a style that is demanded by the highly competitive mobile phone industry. Table 1 summarizes the advantages and limitations of the lithium-ion polymer battery.

Table 1. Advantages and limitations of lithium-ion polymer batteries.Advantages: Very Low Profile -- batteries that resemble the profile of a credit card are feasible.
Flexible Form Factor -- manufacturers are not bound by standard cell formats. With high volume, any reasonable size can be produced economically.
Light Weight -- gelled rather than liquid electrolytes enable simplified packaging, in some cases eliminating the metal shell.
Improved Safety -- more resistant to overcharge; less change for electrolyte leakage.
Limitations: Lower Energy Density and Decreased Cycle Count Compared to Lithium-Ion -- the potential for improvements exist.
Expensive to Manufacture -- once mass-produced, the lithium-ion polymer has the potential for lower cost. A reduced control circuit offsets higher manufacturing costs.




Credits:

Isidor Buchmann
President
Cadex Electronics Inc.
Richmond, BC, Canada

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Post by sg219 » Sat Nov 20, 2004 1:38 am

A Breif History of the Battery.


History of Batteries

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Post by betty.k » Sat Nov 20, 2004 5:59 am

this place has good info on all types of batteries and charging http://www.batteryuniversity.com/
i used to be cool
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