Notebook Battery Guide

[chrisyano]

Notebook Battery Guide
By Chris Yano

Notebook batteries are a common topic of discussion, and the vast majority of questions about them deal with prolonging their lives. There is a lot of information about Lithium Ion (hereafter Li-Ion) batteries to wade through. There are a lot of misconceptions floating around as well. This simple guide addresses the most common notebook battery questions and concerns.

Quick Reference: Simple Guidelines

Frequently Asked Questions:

How long will my battery last?
Connected or Disconnected when on AC power?
How do I prolong my batteries’ life?
Battery Wear Estimates?
Considering a second battery?
Can I use a battery from another system in my new laptop if it fits? Can I use a generic battery in my laptop?
What about recalls and exploding batteries?

[chrisyano]

How long will my battery last?

Your notebook battery will deteriorate over time whether you use it or not. Although the Li-Ion industry does not publicize this fact, your battery’s clock began ticking the moment it was assembled. The elements inside your battery slowly react with each other, eventually rendering the battery unable to supply the required power to your notebook. In addition, your battery is rated to last between 300 and 800 charge/recharge cycles. It will gradually lose charge capacity rather than abruptly fail to power your notebook.

The general consensus is that notebook batteries last one to three years. While you can slow the battery’s aging and loss of capacity, you cannot stop either decline. The temperature of the battery, combined with the amount and nature of its usage contribute significantly to your battery’s lifespan. You can ease the aging process with some care and maintenance.

Temperature

Lower temperatures slow down the self-discharge (loss of charge while disconnected) and aging process of the elements within your battery. Therefore it follows that higher temperatures shorten the life of your battery. Leaving your battery connected while on AC power causes the internal temperature of the battery to rise. Removing your battery and storing it in a cool, dry place will help to slow the aging process. Keeping your notebook in a hot environment is also detrimental to your battery.

Amount of Usage

The Lithium-Ion batteries used in notebooks are rated to handle between 300 and 800 charge/discharge cycles. Some of these cycles are used when you leave your battery connected to your notebook while on AC power. On AC power, the notebook will routinely “top-off” the battery when its charge reaches predetermined levels (i.e. 95%). Removing your battery and storing it in a cool, dry place will help to preserve some of these cycles.

Nature of Usage

Li-Ion batteries do not suffer from the memory-effect (requiring complete discharge before recharging to avoid loss of capacity) like older rechargeable batteries. Regular full discharge/recharge cycles result in an increased loss of capacity per cycle. A series of partial discharge cycles are better for Li-Ion batteries than a single full discharge. You should, however, calibrate your battery routinely.

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Connected or Disconnected when on AC Power?

Things to consider if:

You are removing the battery while on AC power:
Pros:
• Preserves charge cycles
• Keeps the battery temperature lower thus slowing the aging process
Cons:
• Lose the battery as backup power during power outages and voltage drops
• Unsaved work will be lost and data may be corrupted without backup power
• UPS (uninterruptible power supply) needed to serve as backup power source

You are leaving the battery connected while on AC power:
Pros:
• Battery serves as backup power during power outages and voltage drops
• More convenient for “grab-and-go” use
• Battery doesn’t require sufficient warming time (as it would after being stored in the refrigerator)
Cons:
• Loss of charge cycles
• Battery’s temperature is higher on AC power resulting in accelerated aging

[chrisyano]

Prolonging your Battery’s Life

• Calibrate your battery with a full discharge every 30 charges to help the battery’s fuel gauge remain accurate. Run the battery down to the automatic cut-off point of your notebook before recharging.
• Avoid repetitive and regular full discharges. Li-Ion batteries will lose less charge capacity when partially recharged. Recharging at a 10 to 20% charge level is recommended.
• Disconnect the battery and store it in a cool, dry place. The optimal charge level is 40% for prolonged storage. Storing the battery with a low charge will result in permanent damage or battery failure.
• If you store your battery in a refrigerator, use a sealed plastic bag to keep moisture out. Allow the battery to warm to room temperature before using or recharging it.

[chrisyano]

Battery Wear Estimates

Hardware utility applications such as Notebook Hardware Control can estimate the amount of wear your notebook’s battery has experienced. Many are alarmed when their two-week-old battery registers a 16% battery-wear-level. Understandably, they are concerned that their battery is dying and will not be useful for long. Unless you were given an older battery with your new system, you can take those alarmingly high figures with a grain of salt.

Unless the application you are using was designed with the exact specifications of your notebook and battery, it is a generic program that estimates battery wear levels. There are countless variables that can affect the outcome of this estimate (notebook-specific configurations, BIOS and software settings, battery specifications, etc.). The utility can not possibly communicate perfectly with every notebook system and battery model available, so it takes what information it can and calculates its best guess. To give you an idea of how inaccurate these figures can be, my five month-old battery has 0% battery wear according to Notebook Hardware Control.

[chrisyano]

Considering a Second Battery?

As mentioned above, the elements inside your Li-Ion battery will deteriorate over time regardless of what you do. This is why you may want to consider delaying that second battery purchase – to stagger the aging process of multiple batteries. You may find that you do not need a second battery after all. If you do find that you need an extra battery, however, it is recommended that you buy only when needed for this reason.

[chrisyano]

Can I use a battery from another system in my new laptop if it fits?
Can I use a generic battery in my laptop?

Li-Ion cells are permanently damaged when their charge drops below certain levels. If the voltage gets too low, the battery will stop working and become unsafe to use. Therefore all systems powered by Li-Ion batteries have a predefined threshold set to shut down at certain levels of discharge. As a result, Li-Ion batteries are made to the exact specifications of the systems they are designed for, and vice-versa. This is where batteries from another system or low-cost generic batteries may not be compatible. If the thresholds of the system and battery do not match, there is a risk of power cutting off at the wrong moment. This may lead to unsaved work being lost, data corruption, or irreversible battery damage.

In addition, generic low-cost batteries are not made with the high safety standards of official batteries. Main-brand batteries use only approved safety circuits in their battery packs whereas there is no regulation of off-brand battery production. This, as well as attempts by notebook manufacturers to ensure approved batteries are used, is responsible for the higher cost of official batteries. There have been reports of notebooks rejecting generic batteries (to avoid usage of potentially dangerous batteries) without software changes (bypassing the security system). Some generic batteries even fail to work altogether.

There are subtle differences in design, manufacture, and the operation of generic and official batteries which may or may not cause problems for you. For every person that has had problems using generic batteries, there is another who has had no problems whatsoever. You must decide if saving a little money on a replacement battery is worth the potential risks.

[chrisyano]

What about recalls and exploding batteries?

Recently there were a number of reports of exploding batteries. Naturally, you may be concerned about the safety of your notebook’s battery. The cause of recent battery explosions has been traced to metal particle contamination of internal components in batteries produced in certain factories. A recall is in place for the batteries at risk of suffering from this defect.

Here is the recall list from October 23, 2006, where you can check to see if your battery is at risk.

[chrisyano]

Quick Reference: Simple Guidelines

• Heat is your battery’s worst enemy. Avoid keeping your battery in hot places such as your car during the daytime.
• A full discharge puts more strain on your battery than several partial discharges. You do not need to worry about battery memory with Li-Ion batteries. Get into the habit of recharging the battery when it reaches 10-20%.
• Never discharge your battery to 0% – as this can render your battery useless.
• Calibrate your battery’s fuel gauge by doing a full discharge every 30 cycles. Run the battery to the cut-off point in your notebook to keep the battery’s fuel gauge accurate.
• If you will be on AC power for an extended period of time, you can prolong your battery’s lifespan by removing it and putting it into prolonged storage.
• Prolonged storage should be done with a 40% charge-level and in a cool, dry place. Some experts recommend you place the battery in your refrigerator. Use a sealed plastic bag to keep moisture out if you do this.
• Do not freeze your battery.
• Allow a stored battery to warm to room temperature completely before using or recharging it.

Further Reading
• Battery University Homepage
• Batteries in a Portable World
• Wikipedia
• laptopbattery.net Maintenance Tips

[Andrew]

Wow, that's pretty thorough. Without getting into the science and chemical reaction involved with Li-Ion batteries that's about all you need to know.

One thing some manufacturers are offering now is "Express Charge", specifically Dell. While I like that feature, a word of warning, Express Charge can be a killer on the battery as the faster you charge a battery the more it tends to warp the cells. So in the long run a trickle/slow charge of a battery is better. However, tell that to the guy that has an hour layover in an airport and needs to charge a battery as fast as possible. I kind of wish notebook makers offered a way to toggle how fast the battery charges so you could trickle charge when it doesn't matter and fast charge when you really need to charge the battery fast.

Anyway, that's a bit off topic. I have nothing else to add to this very thorough post, but if someone has some more pointers here please post!