HP clocks up 24-hour laptop battery life

HP has beaten Dell - in the laptop battery longevity hype stakes, that is. It's produced a notebook with a full-day runtime, it claims - five hours longer than Dell's most recent battery life boast.

Register Hardware readers will not be surprised to learn there's a catch. Several catches, in point of fact.

First, you need to add an optional-extra secondary battery to the EliteBook 6930p to come within striking range of the claimed duration.

Punters will also need to make sure their 6930p uses not only one of Intel's new 80GB solid-state drives but also an "HP Illumi-Lite LED display". They'll have to run Windows XP - not Vista, you'll note; so much for the latest technology.

HP's EliteBook 6930p: all day runtime?

They'll also have to install new Intel graphics drivers - which presumably is pre-set to reduce the backlight and to perform other power-saving integrated GPU tweaks - and a new Bios from HP.

Do all that, and you might get you 24 hours of battery life. But not yet - HP's miracle screen, which "boosts battery run time by up to 4 hours compared to traditional LCD displays", won't be available as a system-configuration option until October.

HP also noted that "battery life will vary depending on the product model, configuration, loaded applications, features, and power management settings", so it's entirely possible you have to max out the laptop's power-conservation settings and turn the display down to its minimum brightness level to get the claimed runtime.

HP - as per all other laptop makers with the exception of Dell - didn't say how it had tested its machine to get the claimed battery life.

When Dell unveiled its 19-hour laptop - again, that's with an extra battery on board - it said it used the MobileMark benchmark to come up with that figure.

HP didn't say how much the suitably specced EliteBook will cost, but given the price of the Intel SSD, it's likely to be at least $600 on top of any given currently available 6930p HDD configuration.

By Tony Smith - reghardware.co.uk

Sharing battery knowledge

It is my pleasure bringing to you Battery University, the institution for Learning the basics about batteries. In each of the short commentaries you will read about the best battery choices, new battery technologies and ways to make your batteries last longer. Practical, down-to-earth battery information is sometimes hard to find. Battery manufacturers are often too optimistic with their promises and only emphasize positive features.

I have a background in radio communications and studied the behavior of rechargeable batteries in practical, everyday applications for several decades. In desiring to share this battery knowledge with you; I wrote several articles addressing the strength and limitations of the battery. These articles have been published in various trade magazines in the USA, Canada and Europe. I later compiled the material and wrote my first book entitled Batteries in a Portable World - A Handbook on Rechargeable Batteries for Non-Engineers.

The 88-page first edition appeared in 1997 and covered such topics as the memory effect of nickel-cadmium batteries and how to restore them. Some readers commented that I favored nickel-cadmium over nickel-metal-hydride. Perhaps this observation is valid and I have taken note. Having been active in the mobile radio industry for many years, much emphasis is placed on battery longevity, a quality that is true of nickel-cadmium. Today's battery users prefer small size and want maximum runtime. Longevity may be less important, especially in the fast-moving consumer market.

The second edition of Batteries in a Portable World was published in 2001. With 18 Chapters and 300 pages, this book has been extended to include new battery technologies and various field applications.
In May 2001, the Battery Information Website www.buchmann.ca was launched, making the contents of the book available to the world at large. Battery articles have been added to complement the book and serve readers of non-English languages. A search engine was installed to help you find topics of interest. The Battery Information Website is sponsored by Cadex Electronics Inc., the manufacturer of advanced battery analyzers chargers and PC software.

Getting the Most from your Batteries has consistently been first choice. People want to know how to care for their batteries to get maximum runtime and dependable service. Proper Charge Methods is also very much in the hearts of the battery users. A surprise was Internal Battery Resistance in third position. This subject is of growing concern with digital equipment that puts high demands on the battery. A seemingly good battery often fails to deliver the heavy current bursts because of elevated internal resistance caused by aging batteries.

Battery University is based on the book Batteries in a Portable World and will address such issues as the choice of battery chemistries, physical battery packs, charge and discharge methods, runtime concerns, the 'smart' battery, internal battery resistance, getting the most of your batteries and much more.

Batteries in a Portable World is written for the non-engineer. It addresses the use of the battery in the hands of the general public, far removed from protected lab environments of the manufacturer. Some information contained in this book was obtained through tests performed in Cadex laboratories; other knowledge was gathered by simply talking to diverse groups of battery users. Not all views and opinions expressed in the book are based on scientific facts. Rather, they follow opinions of the general public, who use batteries. Some difference of opinion with the reader cannot be avoided. I am prepared to accept the blame for any discrepancies. The book is available from www.buchmann.ca at $29.50US
I would like to hear your comments on Battery University. After all, battery technology is not black and white but has many shades of gray. I hope you will find these lessons interesting and helpful.

About the Author
Isidor Buchmann is the founder and CEO of Cadex Electronics Inc., in Vancouver BC. Mr. Buchmann has a background in radio communications and has studied the behavior of rechargeable batteries in practical, everyday applications for two decades. Award winning author of many articles and books on batteries, Mr. Buchmann has delivered technical papers around the world.
Cadex Electronics is a manufacturer of advanced battery chargers, battery analyzers and PC software. For product information please visit www.cadex.com.

Zapping

Zapping:
The process of applying a momentary high current pulse to a battery to improve performance. Zapping is said to improve new NiCd batteries but does not restore weak packs.

Voltage-limiting charger

Voltage-limiting charger:
A charger that limits the maximum voltage to a battery but allows the current to drop towards the end of charge. A voltage-limiting charge may also include current-limiting. (Typically used on lead acid and Li?ion battery chargers).

Voltage limit

Voltage limit:
The voltage value beyond which a battery is not permitted to rise on charge or fall on discharge.

Voltage delay

Voltage delay:
During open circuit storage, some battery systems develop a passivation film on the surface of the active material. On the initial discharge, these batteries demonstrate a momentarily lower than normal voltage until this film is removed by the discharge.

Topping Charge

Topping Charge:
To complete the fast charge, a topping charge is applied that continues charging the battery for 30 minutes or longer at a lower current. Typically used for nickel-based batteries.

Trickle charge

Trickle charge:
Maintenance charge to compensate for the battery's self-discharge.

Thermal runaway

Thermal runaway:
A condition whereby an electrochemical cell will overheat and destroy itself through internal heat generation. This may be caused by overcharge or high current discharge and other abusive conditions.

Thermal battery voltage

Thermal battery voltage:
Batteries are non-linear systems. The equations, which govern the battery's response, becomes linear below 25mV/cell at 25°C. This voltage is called the battery thermal voltage.

System Management Bus (SMBus)

System Management Bus (SMBus):
A commonly used protocol for the 'smart' battery.

Supercapacitor

Supercapacitor:
A capacitor that can store a high amount of energy. Supercapacitors hold about one tenth the energy of a nickel or lithium-based battery.

Sulfation

Sulfation:
The growth of lead sulfate crystals in lead acid batteries, which inhibits current flow. Sulfation is caused by storage at low state-of-charge.

State-of-Health (SoH)

State-of-Health (SoH):
A measurement that reflects the state-of-health of a battery, taking into account charge acceptance, internal resistance, voltage and self-discharge.

State-of-Charge (SoC)

State-of-Charge (SoC):
A measurement that reflects the state-of-charge of a battery. The SoC alone is not a valid indicator of the battery's runtime. The SoC readings will indicate 100 percent, even if a battery whose acceptance has dropped to 50 percent is fully charged.

Spinel

Spinel:
A family of compounds that have a specific chemical structure. In lithium-ion batteries, the structure is manganese-based.

Spectroscopy

Spectroscopy:
Same terminology as Electrochemical Impedance Spectroscopy.

Soft cell

Soft cell:
A cell whose voltage rises above its defined boundaries during charging. This voltage rise may be caused by high cell impedance, cold battery temperature or lack of electrolyte.

'Smart' battery

'Smart' battery:
Also known as an 'intelligent battery.' A battery pack containing internal circuitry that enables communication between the battery and the user.

Slow charge

Slow charge:
Typically an over-night charge lasting 10 to 16 hours at a charge current of 0.1C. A battery does not require instant removal when fully charged.

Single wire bus

Single wire bus:
Simplified 'smart' battery using only one wire for digital communications to the outside world.

Self-discharge

Self-discharge:
Capacity loss during storage due to the internal leakage between the positive and negative cell plates.

Secondary battery

Secondary battery:
A battery that is rechargeable by reversing its chemical reaction.

Reverse load charge

Reverse load charge:
A charge method that intersperses discharge pulses between charge pulses to promote the recombination of gases generated during fast charge. Reverse load charge also helps to reduce memory.

Residual capacity

Residual capacity:
The charge capacity remaining in a battery prior to charge.

Resistance

Resistance:
Opposition to electrical current flow. Batteries with high internal resistance are not able to deliver heavy current pulses or elevated loads.

Recondition

Recondition:
A deep discharge below 1.0V/cell with a controlled current, causing a change to the molecular structure of the cell and a rebuilding of its chemical composition. Recondition helps break down large crystals to a more desirable small size, often restoring the battery to its full capacity. Applies to nickel-based batteries.

Reactance

Reactance:
The presence of inductive and capacitive resistance.

Rapid charge

Rapid charge:
Same terminology as quick charger.

Quicktest

Quicktest™:
A method to quick test the state-of-health of a battery.

Quick charger

Quick charger:
A charger that charges a battery in 3 to 6 hours.

Protection circuit

Protection circuit:
Circuitry built into the battery pack to maintain the safety of the battery and equipment in case of improper handling.

Prismatic cell

Prismatic cell:
The positive and negative plates are stacked rather than rolled.

Primary battery

Primary battery:
A non-rechargeable battery. The active materials of a primary battery undergo an irreversible change during discharge.

Pouch cell

Pouch cell:
A battery in which the typical metallic cylinder and glass-to-metal electrical feed-through is replaced with a flexible, heat-sealable foil package.

Polymer

Polymer:
An ionic conductor that is an electrical insulator put passes ions.

Passivation layer

Passivation layer:
A resistive layer that forms in some cells after prolonged storage. This layer must be broken to enable proper operation. Applying charge/discharge cycles often help in preparing the battery for use.

Overcharge

Overcharge:
Charging a battery after it reaches full charge. On overcharge, the battery can no longer absorb charge and the battery heats up.

Organic

Organic:
Carbon-based solvent.

Ohmtest

Ohmtest™:
A measurement that reflects the internal resistance of a battery.

Ohmic resistance

Ohmic resistance:
Electrical resistance void of reactance.

Nominal voltage

Nominal voltage:
The cell voltage that is accepted as an industrial standard. (Cell voltages of 1.20 and 1.25V are used for NiCd and NiMH batteries).

Nickel cadmium battery

Nickel cadmium battery:
A rechargeable battery using cadmium as the negative electrode.

Negative delta V (NDV)

Negative delta V (NDV):
A drop in battery voltage, which occurs when a sealed NiCd or NiMH battery reaches the full charge state and goes into overcharge.

Milliampere-hour

Milliampere-hour:
A battery capacity or rating. A battery that provides a current of 1000mA for 1 hour is rated at 1000mAh (or 1Ah).

Memory

Memory:
Reversible capacity loss in NiCd and NiMH batteries. The modern definition of memory commonly refers to a change in crystalline formation from the desirable small size to a large size. Memory is often used to describe any reversible capacity loss on nickel-based batteries.

Maintenance Requirements

Maintenance Requirements:
Battery maintenance prolongs battery life. Nickel-based batteries need a periodic full discharge to eliminate 'memory'. Lead acid batteries require periodic equalizing charge. Lithium-based batteries need little maintenance.

Manganese

Manganese:
A metallic chemical element.

Matrix

Matrix:
The set of battery parameters stored in the battery adapter to enable the Cadex Quicktestä function.

Load current

Load current:
The discharge current delivered to a battery-powered device.

Lithium polymer

Lithium polymer:
A rechargeable battery using solid polymer as electrolyte. Most lithium polymer batteries require heat to promote conductivity.

Lithium ion polymer

Lithium ion polymer:
A rechargeable battery similar to the Li?ion but with a solid polymer as electrolyte. Some gelled conductive material is added to promote conductivity.

Lithium ion battery

Lithium ion battery:
A battery dependent on the flow of lithium ions. The lithium metal on the negative electrode is replaced with carbon to improve safety.

Lithium battery

Lithium battery:
A battery using lithium metal as negative electrode. Most lithium batteries are non-rechargeable.

Lead acid battery

Lead acid battery:
Rechargeable battery commonly used for wheeled and stationary applications. The plates consist of lead-antimony alloy.

Ion

Ion:
A charged particle that is combined with a particle of opposite charge to produce a chemical salt.

Intrinsically Safe

Intrinsically Safe:
A battery with built-in protection circuitry. These batteries are used primarily in explosive environments.

Intelligent battery

Intelligent battery:
Also known as a 'smart' battery. The battery pack contains internal circuitry to enable communication between the battery and the user.

Impedance

Impedance:
Resistance to electrical current created by reactance and ohmic resistance

Internal resistance

Internal resistance:
Resistance to electrical current inside a cell or battery pack.

Hydrogen battery

Hydrogen battery:
A rechargeable battery commonly used for space applications.

Graphite

Graphite:
A form of carbon.

Fuzzy logic

Fuzzy logic:
A mathematical technique used to obtain an approximate output reading derived from various analog inputs. Fuzzy logic can be utilized to quick-test batteries.

Fuel cell

Fuel cell:
An electrochemical device that generates electricity by converting oxygen and hydrogen into water.

Float charge

Float charge:
Similar to trickle charge. Compensates for the self-discharge on a lead acid battery.

Fast charge

Fast charge:
Typical fast charge time for a nickel-based battery is 1 hour; lithium-based is 3 hours. The fast-charger detects the state-of-charge and switches to trickle charge when full-charge is reached.

Exercise

Exercise:
Commonly understood as one or several discharge cycles to 1V/cell with subsequent recharge. Used to maintain NiCd & NiMH batteries.

Equalizing Charge

Equalizing Charge:
With time, the charge levels of individual cells of a large battery tend to become slightly unbalanced. The equalizing charge applies an elevated charge voltage for a few hours to balance the cells. Used mainly for large lead acid cells.

Energy density

Energy density:
The amount of energy a cell can contain. Gravimetric energy is the watt-hours a battery is capable of providing per given weight (pound or kilogram), and volumetric energy is the watt-hours per given size (cubic inch or cubic centimeter). The energy is defined as nominal battery voltage multiplied by rated capacity.

Energy

Energy:
Voltage multiplied by current expressed in watts.

Electrolyte

Electrolyte:
A non-metallic conductor of electricity (typically liquid) between the positive and negative electrodes of a battery. The current is carried by the physical movement of ions.

Electrode

Electrode:
Conducting element within a cell in which an electrochemical reaction occurs. Normally includes active materials plus conductive and supportive elements.

Electrochemical Impedance Spectroscopy (EIS)

Electrochemical Impedance Spectroscopy (EIS):
Used to investigate electrochemical characteristics of batteries. The method applies an AC potential at varying frequencies to an electrochemical cell and the current response is measured.

Dumb battery

Dumb battery:
A battery which contains no electronic circuitry with which to communicate digitally.

Double layer capacitor

Double layer capacitor:
Capacitor with high farad rating. The high capacity is made possible by a double layer formed near the carbon electrode surface.

Cylindrical cell

Cylindrical cell:
The positive and negative plates are rolled up and placed into a cylindrical container.

Cycle life

Cycle life:
The number of cycles a battery provides before it is no longer usable. (A battery is considered non-usable if its nominal capacity falls below 60 to 80 percent).

Cycle

Cycle:
A process consisting of a single charge and discharge of a rechargeable battery.

Current-limiting chargers

Current-limiting chargers:
A charger that keeps the charge current constant during the charge process but allows the voltage to fluctuate (typically used on NiCd and NiMH chargers).

Coke

Coke:
Coal from which most of the gases have been removed by heating. Coke is used as an industrial fuel.

Coulomb

Coulomb:
A unit of electric charge used to measure the ingoing and outgoing discharge current of a battery. One coulomb (1C) is equal to the electricity transferred by a current of one ampere in one second. (The maximum energy a molecular weight of a chemical system can deliver is one faraday of energy or 96495.7C which is the equivalent of 26.8Ah of capacity.)

Co-generation

Co-generation:
The utilization of heat produced as byproduct in converting oxygen and hydrogen to electricity in a fuel cell. The heat is used to drive steam turbines.

Charge

Charge:
The process of replenishing or replacing the electrical charge in a rechargeable cell or battery.

Cell reversal

Cell reversal:
The stronger cells of a battery (several cells connected in series) impose a voltage of reverse polarity across a weaker cell during a deep discharge.

Cell mismatch

Cell mismatch:
Cells within a battery pack containing different capacity and voltage levels.

Capacity offset

Capacity offset:
A correction factor applied to the rating of a battery if discharged under different C?rates from the one rated.

Capacity

Capacity:
The electrical energy content of a battery as expressed in ampere-hours. Capacity is the total number of ampere-hours or watt-hours that can be withdrawn from a fully charged cell or battery under specific condition of discharge. The capacity is measured by observing the time it takes to discharge a battery at a constant current until a specified cut-off voltage is reached.

C-rate

C-rate:
Unit by which charge and discharge times are scaled. A battery rated at 1000mAh provides 1000mA for one hour if discharged at 1C. A discharge of 1C draws a current equal to the rated capacity. The same battery discharged at 0.5C would provide 500mA for two hours.

C-code

C-code:
Abbreviation of 'configuration code.' This information is typically stored in a battery adapter and configures the analyzer to the correct battery settings when installed.

Button cell

Button cell:
A miniaturized battery. Most rechargeable button cells are NiCd or NiMH.

Battery cycle

Battery cycle:
A full charge followed by a full discharge (or the other way around).

Ampere-hours (Ah)

Ampere-hours (Ah):
A measure of energy that is provided to or drawn from a battery. (A current of one ampere for one hour equals 1Ah).

Ambient temperature

Ambient temperature:
The average temperature of the battery's surrounding medium, typically air.

How to prolong lithium-based batteries

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 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 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 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 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.

Figure 1: Permanent capacity loss of lithium-ion as a function of temperature and charge level.
High charge levels and elevated temperatures hasten permanent capacity loss. Improvements in chemistry have increased the storage performance of lithium-ion batteries.

The mentioning of limited service life on lithium-ion has caused concern in the battery industry and I will need to add some clarifications. Let me explain:
If someone asks how long we humans live, we would soon find out that the longevity varies according to life style and living conditions that exist in different countries. Similar conditions exist with the batteries, lithium-ion in particular. Since BatteryUniversity bases its information on the feedback from users as opposed to scientific information derived from a research lab, longevity results may differ from manufacturer' specifications. Let's briefly look at the various living conditions of the lithium-ion battery.

The worst condition is keeping a fully charged battery at elevated temperatures, which is the case with running laptop batteries. If used on main power, the battery inside a laptop will only last for 12-18 months. I must hasten to explain that the pack does not die suddenly but begins with reduced run-times.

The voltage level to which the cells are charged also plays an important role to longevity. For safety reasons, most lithium-ion cannot exceed 4.20 volts per cell. While a higher voltage boosts capacity, the disadvantage is lower cycle life. Figure 2 shows the cycle life as a function of charge voltage.

Read more this article at http://www.batteryuniversity.com/parttwo-34.htm

4 tips to extend the life of your laptop battery

In a 2002 survey by chipmaker Intel, 57% of laptop users said they wished their batteries lasted longer. And that is wishful thinking, according to Isidor Buchmann, president and founder of Cadex Electronics in

Vancouver, B.C., Canada. He suggests that although batteries become about 10% more efficient every year, the average PC's power needs also increase by about the same amount. Result: The average battery life is still painfully short (just three to four hours for most laptop models).

But you don't have to end up sitting in a waiting area, staring at a darkened screen, like I was. Here are four tried-and-true tips to extend the life of your laptop battery. Why should you take advice from a guy who couldn't keep his own unit charged? Read on if you want to hear my sad excuse.

1. Power down all nonessential functions.

Switch it off if you're not using it. Many business travelers already know that you don't want to take the DVD player for a spin on the plane, and that every time you hit "save" it can set the hard-drive whirring, which devours even more power. "But users often also forget to turn off their wireless card when they are no longer using it but are still using their computer," notes Mike Fuller, executive vice president of PC Laptops, a Sandy, Utah, laptop manufacturer. "When the wireless card is on, it still continually searches for networks." In Windows XP, click on "Power Options" in your control panel. It allows you to reduce the power consumption of any number of your computer devices or of your entire system.

2. Stay out of extreme temperatures.

The technology that powers you battery isn't terribly complicated. But it's important to understand a little bit about the chemistry behind batteries, and how that can affect your work. Specifically, temperatures can affect the performance of your battery. It's best to use (and especially charge) your batteries at room temperatures. Extreme conditions can drain your battery quickly. Also, avoid partial charges and use the battery until it is dead. Battery experts liken partial charges — and discharges — to eating a cup of lard every day. It significantly shortens your battery's life. Considering that a lithium-ion battery can explode if it's improperly used, it could also shorten your life.

3. Let your laptop do the saving.

Not every computing device handles a power source in the same way. Some of the more sophisticated laptops, which are designed with business travelers in mind, are misers when it comes to using power. And that's a good thing — if you can remember to take advantage of it. "Most users make the mistake of simply not choosing to use a product's built-in ability to conserve battery life," says Dan Coffman, a senior product manager for PC manufacturer ViewSonic. How do you harness your PC's built-in ability to save? Consult your user manual. Often, calibrating your laptop is as easy as double-clicking on the battery icon in the toolbar.

4. Always, always carry a spare device that uses batteries.

How obvious is that? Well, if you're trying to keep under the onerous new airline weight-limits, it isn't. But as Rick Thompson, director of engineering at Valence Technology in Austin, Texas, observes, "the availability of 'free' power outside of your hotel room is not predictable." That's a nice way of saying it. In fact, I sometimes think airport terminals, car-rental facilities and hotels try to hide the power outlets from us to keep us from accessing their free power.

Thompsonrecommends a system that can simultaneously charge a second portable device such as a cell phone or PDA, allowing you to multitask your battery operations. If you've stuck with me long enough to hear my pitiful excuse for running my laptop battery down, here it is: My 2-year-old-son, Aren, uses my laptop to watch "The Wiggles" while I'm on the road (if you don't know who "The Wiggles" are, consider yourself fortunate). Aren decided to pull the power chord while he was watching an episode and used up all the power to run the DVD player. By the time I got to the PC, all the juice was gone.

I should probably thank Aren. He taught me how fast a DVD can run down a lithium-ion battery (in almost no time). Incidentally, he's also demonstrated how impact-resistant a battery can be (surprisingly) and that at least some of those warnings about the battery coming into contact with liquids are exaggerated. You'd be amazed at how well a battery holds up to liquids, especially whole milk.

By Christopher Elliott

Top 15 Ways to Extend Your Laptop’s Battery Life

Laptops tend to lose their charm quickly when you’re constantly looking for the nearest power outlet to charge up. How do you keep your battery going for as long as possible? Here are 15 easy ways to do so.

1. Defrag regularly - The faster your hard drive does its work - less demand you are going to put on the hard drive and your battery. Make your hard drive as efficient as possible by defragging it regularly. (but not while it’s on battery of course!) Mac OSX is better built to handle fragmentation so it may not be very applicable for Apple systems.

2. Dim your screen - Most laptops come with the ability to dim your laptop screen. Some even come with ways to modify CPU and cooling performance. Cut them down to the lowest level you can tolerate to squeeze out some extra battery juice.

3. Cut down on programs running in the background. Itunes, Desktop Search, etc. All these add to the CPU load and cut down battery life. Shut down everything that isn’t crucial when you’re on battery.

4. Cut down external devices - USB devices (including your mouse) & WiFi drain down your laptop battery. Remove or shut them down when not in use. It goes without saying that charging other devices (like your iPod) with your laptop when on battery is a surefire way of quickly wiping out the charge on your laptop battery.

5. Add more RAM - This will allow you to process more with the memory your laptop has, rather than relying on virtual memory. Virtual memory results in hard drive use, and is much less power efficient. Note that adding more RAM will consume more energy, so this is most applicable if you do need to run memory intensive programs which actually require heavy usage of virtual memory.

6. Run off a hard drive rather than CD/DVD - As power consuming as hard drives are, CD and DVD drives are worse. Even having one in the drive can be power consuming. They spin, taking power, even when they?re not actively being used. Wherever possible, try to run on virtual drives using programs like Alcohol 120% rather than optical ones.

7. Keep the battery contacts clean: Clean your battery’s metal contacts every couple of months with a cloth moistened with rubbing alcohol. This keeps the transfer of power from your battery more efficient.

8. Take care of your battery - Exercise the Battery. Do not leave a charged battery dormant for long periods of time. Once charged, you should at least use the battery at least once every two to three weeks. Also, do not let a Li-On battery completely discharge. (Discharing is only for older batteries with memory effects)

9. Hibernate not standby - Although placing a laptop in standby mode saves some power and you can instantly resume where you left off, it doesn’t save anywhere as much power as the hibernate function does. Hibernating a PC will actually save your PC’s state as it is, and completely shut itself down.

10. Keep operating temperature down - Your laptop operates more efficiently when it’s cooler. Clean out your air vents with a cloth or keyboard cleaner, or refer to some extra tips by LapTopMag.com.

11. Set up and optimize your power options - Go to ‘Power Options’ in your windows control panel and set it up so that power usage is optimized (Select the ‘max battery’ for maximum effect).

12. Don’t multitask - Do one thing at a time when you’re on battery. Rather than working on a spreadsheet, letting your email client run in the background and listening to your latest set of MP3’s, set your mind to one thing only. If you don’t you’ll only drain out your batteries before anything gets completed!

13. Go easy on the PC demands - The more you demand from your PC. Passive activities like email and word processing consume much less power than gaming or playing a DVD. If you’ve got a single battery charge - pick your priorities wisely.

14. Get yourself a more efficient laptop - Laptops are getting more and more efficient in nature to the point where some manufacturers are talking about all day long batteries. Picking up a newer more efficient laptop to replace an aging one is usually a quick fix.

15. Prevent the Memory Effect - If you’re using a very old laptop, you’ll want to prevent the ‘memory effect’ - 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 most laptops have) which do not suffer from the memory effect.

Bonus Tip #1: Turn off the autosave function. MS-Word’s and Excel’s autosave functions are great but because they keep saving regular intervals, they work your hard driver harder than it may have to. If you plan to do this, you may want to turn it back on as the battery runs low. While it saves battery life in the beginning, you will want to make sure your work is saved when your battery dies.

Bonus Tip #2: Lower the graphics use. You can do this by changing the screen resolution and shutting off fancy graphic drivers. Graphics cards (video cards) use as much or more power today as hard disks - Thanks Andrew

Update 7/7/07: Bonus Tip #1 to give caution about turning off autosave, tip #8 to change information about discharging batteries - thanks to all who pointed it out. Added Bonus tip #2, Tip #1 to add in clause in regards to Mac OSX, Tip #1 about the spinning of hard drives - thanks to all who pointed it out