FAQ and Battery Tips
A: The best battery is design for small size and long runtime but has a limited cycle life. Another pack may be built for durability and is big and bulky. A third may have high energy density and long durability but is made for a special application and is too expensive for the average consumer. A lithium-based battery can be designed for maximum energy density but its safety would be compromised.
A: CMOS & clock backup batteries perform the same function in desktop and laptop computers: when the computer is turned off, the battery maintains the time and date, thus insuring their accuracy when the system is once again restarted. More importantly, the battery saves the computers BIOS setup configuration, which allows the system to efficiently reboot once it is restarted. The computer knows what type of hard drive it is dealing with, etc. Not surprisingly, these batteries are known alternatively as CMOS batteries, Real Time Clock (RTC) batteries, or simply internal batteries.
The most common CMOS battery chemistries are Lithium, Nickel Cadmium (Ni-Cd) and alkaline. They are usually somewhere in the 3 to 7.2 volt range and either solder onto the motherboard or plug in via a snap-in connector (depending upon the computer manufacturers design).
In most cases, replacement of the CMOS battery is an easy task. It is simply a matter of locating the battery on the computer's motherboard, removing it and plugging in a new one. As a rule, internal batteries should be replaced by the same type of battery which was originally used in the machine or according to the manufacturers' specifications. The major exception to this rule is older PCs which were manufactured with a Ni-Cd battery soldered onto the motherboard. These computers usually have a three or four pin male plug, with two of the pins connected via a jumper (this is generally found in the same area of the motherboard as the original battery). This plug gives you the option of leaving the soldered battery in place and replacing it with a plug-in lithium or alkaline battery. Removing the jumper tells the computer to ignore the soldered battery and to look to the pins for its power source. If the motherboard has this provision, you can install a standard PC plug-in battery instead of removing the soldered battery and re-soldering a new one (the standard PC plug-in battery is Electro Battery part number BAT 2005 (lithium) or BAT B40 (alkaline). These batteries are interchangeable).
Some computers have 4 pins on the motherboard, whereas today's plug-in batteries come with a 3 pin connector (one of the pinholes is closed in order to prevent the user from inadvertently plugging the battery in with reversed polarity). If this is the case, you should clip the pin from the motherboard that corresponds to the sealed pinhole on the battery plug. That pin is nonfunctional and by clipping it you ensure that future batteries will not be installed on the motherboard with reversed polarity.
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Ni-Cd batteries are rechargeable, whereas Lithium and alkaline batteries are NOT. Therefore, Lithium and alkaline batteries must be replaced by equivalent batteries of the same type. Attempting to replace these non-rechargeable batteries with a Ni-Cd will result in a nonfunctional battery because the computer lacks the proper charging circuitry to charge the Ni-Cd battery.
If a motherboard lacks the above-discussed male pins for an external battery, the Ni-Cd battery MUST be unsoldered and replaced by a Ni-Cd battery ONLY. Attempting to use an alkaline or lithium battery in place of Ni-Cd on such a board could be hazardous. These batteries are not designed to be recharged, and an attempt to do so may cause the battery to "burst", or explode.
CMOS batteries generally last for two to three years, although some (especially the lithium type) have been known to last much longer. Ironically, the less the computer is used the faster the CMOS battery will run out. This is because when the computer is turned off the battery begins to function. It is recommended to replace the CMOS battery approximately once every two years or when servicing the computer. If the computer has been idle for an extended length of time it is a good idea to change the battery. Changing the battery is a relatively easy and inexpensive task, especially (as were sure many of you out there know) when compared to trying to reboot and configure a computer which has lost its BIOS settings.
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A: Some notebook computers are designed with a dedicated battery for backing up RAM (random access memory) functions when the machine temporarily loses power from the main battery. This feature allows users to change the main battery pack without losing the current applications and settings residing in memory. This is called a "battery hot swap" - switching the main battery pack without having to turn off the computer.
These types of batteries are alternately known as bridge batteries, RAM batteries, auxiliary batteries or resume batteries.
Most RAM batteries are rechargeable Ni-Cd or Ni-MH and will last around 2-3 years. It is recommended that you replace your notebook's RAM battery when replacing the CMOS battery.
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A: Battery run-time on a laptop is difficult to determine. Actual battery running time depends upon the power demands made by the equipment. The use of the screen, the hard drive and other accessories results in an additional drain upon the battery, effectively reducing its running time. The total run-time of the battery is also dependent upon the design of the equipment. Generally, a new Hi-Capacity battery will run 30% to 50% longer than the old battery did when it was new.
A: The recommended storage temperature for most batteries is 15°C (59°F). While lead-acid batteries must always be kept at full charge, nickel and lithium-based chemistries should be stored at 40% state-of-charge (SoC). This level minimizes age-related capacity loss, yet keeps the battery in operating condition even with some self-discharge. While the open terminal voltage of nickel-based batteries cannot be used to determine the SoC accurately, voltage fuel gauging works well for lithium-ion cells. However, differences in the electrochemistry of the electrodes and electrolyte between manufacturers vary the voltage profile slightly. A SoC of 50% reads about 3.8V; 40% is 3.75V. Store lithium-ion at an open terminal voltage of 3.75-3.80V. Allow the battery to rest 90 minutes after charge before taking the voltage reading.
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A: Simple Guidelines
What's the best battery for laptops? Batteries for laptops have a unique challenge - they must be small and lightweight. In fact, the laptop battery should be invisible to the user and deliver enough power to endure a five-hour flight from Toronto to Vancouver. In reality, a typical laptop battery provides only about 90 minutes of service. Many users complain of much shorter runtimes.
A battery in a laptop ages more quickly than in other applications because of heat. During use, the inside temperature of a laptop rises to 45°C (113°F). The combination of high temperature and full state-of-charge promotes cell oxidation, a condition that cannot be reversedonce present. The battery's life expectancy when operating at high temperature is half compared to running at a more moderate 20°C (68°F) or lower. Leaving the laptop in a parked car under the hot sun will also aggravate the situation. All batteries suffer permanent capacity loss as part of elevated temperatures but lithium-ion is affected more than other batteries.
How to calibrate the battery? Most laptop batteries are 'smart'; meaning that they know how much energy is left. Such a feature has definite benefits but the readings are often inaccurate. A laptop may indicate 30 minutes of remaining runtime when suddenly the screen goes dark. Here is the reason why:
With use and time, a tracking error occurs between the chemical battery and the digital sensing circuit. The most ideal use of the 'smart' battery, as far as fuel-gauge accuracy is concerned, is a full charge followed by a full discharge at a constant current. In such a case, the tracking error would be less than 1% per cycle. In real life, however, a battery may be discharged for only a few minutes and the load may vary widely. Long storage also contributes to errors because the circuit cannot accurately compensate for self-discharge. Eventually, the true capacity of the battery no longer synchronizes with the fuel gauge and a full charge and deliberate full discharge will be needed to 're-learn' or calibrate the battery.
There are no standards to tell what constitutes a fully charged and fully discharged battery. Lithium-ion packs are considered fully charged when the limiting voltage (4.20V/cell) is reached and the saturation current has decreased to 3% of the nominal value (50mA on a 1700mAh cell). Some chargers use 5% and 8% as 'ready' criteria.) A full discharge occurs when the cell reaches 3V/cell or lower. At this voltage level, the battery has a remaining capacity of 3 to 10%. Modern batteries adjust to a lower cut-off voltage on high load currents and include temperature compensation.
To calibrate a battery, a full charge and discharge is necessary. One without the other does not constitute a calibration. A problem arises if the battery is recharged after a brief use without providing the opportunity of a full discharge. A forced discharge to "Low Battery" may be needed from time to time.
What happens if no battery calibration is done? Can such a battery be used in confidence? Most 'smart' battery chargers obey the dictates of the chemical cells rather than that of the electronic circuit. In this case, the battery will fully charge regardless of the fuel gauge setting and function normally but the digital readout will become increasingly more inaccurate. If not corrected, the fuel gauge simply becomes a nuisance. Cadex Electronics manufactures 'smart' chargers and battery analyzers that are capable of calibrating a 'smart' battery.
Rechargeable batteries do not die suddenly but gradually get weaker over time. Implementing regular battery maintenance greatly reduces unexpected downtime caused by weak batteries. Manufacturers of portable equipment stress the importance of regular battery testing and endorse the use of battery analyzers.
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If you use your battery for seasonal activities only and must store it for extended periods of time, a battery maintainer is recommended. A maintainer is an electronically controlled charger and will not over charge your battery when hooked up for extended periods of time. Your battery will be ready for use when you are and last longer.
Maintainers are also great for winter starting - A fully charged battery has maximum.
A: Ni-Cd and Ni-MH batteries should be disposed of property. Do not throw these batteries in the trash. Ni-Cd batteries are composed of approximately 20% cadmium, an extremely hazardous element which is environmentally detrimental. While Ni-MH batteries are environmentally friendly, the higher capacity Ni-MH cells still contain trace amounts of cadmium. Be environmentally conscious. Recycle your batteries.
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Do not short-circuit or disassemble your battery. A short-circuit may cause severe damage to the battery. Do not drop, hit or otherwise abuse the battery. This behavior may result in the exposure of the cell contents, which are corrosive. Do not expose the battery to moisture or rain. Keep battery away from fire or from other sources of extreme heat. Do not incinerate. Exposure of battery to extreme heat may result in an explosion.
Certain batteries (i.e. lithium or wet-filled with acid-electric storage), when transported via air have to be properly declared to the air carrier, marked, labeled, and packaged per the Hazardous Materials Regulations. At a minimum, all battery types must be packaged securely and in a manner that prevents the dangerous evolution of heat, for example, by effective insulation of exposed terminals.
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Regularly clean the battery top and terminals. Apply baking soda to any corrosion and flush entire cover with water. Be sure the vent caps are tight before cleaning to prevent water or baking soda from entering into the cells.
A: Yes, but only if they can be kept dry as well. The higher temperature the battery has the more the free flow of ions or self-discharges from the battery. Storing primary batteries (D's, C's, AA's, AAA's, 9 volt, etc.) in a cooler environment slows down this rate of discharge that all batteries experience even when not in use, hence a longer shelf life. However, if this is done, it is important that the batteries be kept as dry as possible by keeping them in an airtight container in the driest part of the refrigerator, the door for example. Long terms exposure to moisture inside the refrigerator can cause internal corrosion to the battery. When removing batteries from the refrigerator, allow them to warm up to room temperature before using them in your device.
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