Eee PC Charging, Battery and Power-Saving Tips

First Charge

When you first take your EeePC out of the box, you have two options. First plug in the unit to mains/wall socket.

The orange charging light will come on and you can let it charge fully for about two hours.
You can power on the unit and use it while it is charging. It will take MUCH longer to fully charge.

Either way, do not unplug the unit until it is fully charged and the orange charging indicator has turned off.

Eee PC Charging, Battery and Power-Saving Tips

Regular Use

The EeePC comes with a lithium-ion battery, so you don’t need to drain the battery before recharging. If you start recharging at the “Battery Low” warning, the Eee 70x will take about 2 to 2 1/2 hours to fully charge while plugged in and powered down while the Eee 900 will take about half that. You can use it while charging, but it will charge much more slowly, especially the 70x series.

You can remove the battery and use the cord as the sole power source.

Battery Life

The Eee is provided with a 5200, 4800, 4400 or (in rare cases) 5800mAh, 4-cell battery. Replacement batteries are available, as well as third-party batteries with greater capacities.

You can expect around 2.5 to 3 hours of battery capacity when being used. Please note that capacity varies significantly according to how it’s used. Please see the section on power saving tips to improve this.

Lithium-ion batteries are typically capable of 300-500 charge/discharge cycles.

Battery care, Weardown and ‘Dead’ batteries

The battery will deteriorate naturally over time. After 2 or 3 years, the battery capacity is likely to be noticeably reduced and you may want to replace the battery. This is called ‘weardown’. It is a gradual process and different batteries within the same batch may wear at different rates.

The battery will deteriorate almost as quickly when not in use, so it doesn’t make sense to buy a replacement to put away for the future.

One of the problems with lithium-ion technology (compared to other types of rechargeable battery) is that this deterioration starts immediately after manufacture, whether or not the battery has been used. This gives lithium-ion batteries a “shelf-life”. Therefore, be wary of cheap replacement batteries which may be old stock that is past its “sell-by date”.

Loss of capacity happens fastest when the battery is fully charged and increases at higher temperatures. The following table shows typical loss of capacity for a lithium-ion battery after one year at full charge and 40% charge (the recommended amount for storage) at different temperatures:

Temperature oC 40% charge 100% charge
0 2% 6%
25 4% 20%
40 15% 35%
60 25% 40%

If you regularly use your Asus plugged in to the mains at home or in the office, then its battery is likely to be kept fully charged and at a temperature around 20oC or more. When the computer is running, the battery’s temperature is likely to be higher than this because the computer gets warm. So, if you use the machine for long periods plugged into the mains, take the battery off and keep it in a cool place (ideally in a fridge).

The battery contains a small microcomputer, which can communicate with the Eee, giving information about load and diagnostic information about the battery. This includes information about how much charge remains. However, it is notoriously difficult to measure the remaining charge in a rechargeable battery and the only two “calibration points” that this circuitry has to work from are “fully charged” and “empty”. If you continually recharge the battery before it is empty, then the second point doesn’t get recalibrated and the accuracy of the ”% charge left” measure (which is never very accurate to start with!) drifts. So it is recommended that you let the battery run right down until the computer tells you it is empty about every 30th charge/discharge cycle to allow for recalibration.

The battery contains a protection circuit preventing it from ever fully discharging. When the battery is at 0% capacity and your loses power, it means the battery has shut itself off, preserving a small amount of charge to prevent permanent damage. If a battery is left in this discharged state for a long time (many weeks), it may become so discharged that it may be dangerous to attempt to recharge it. In this case, a protection circuit inside the battery may permanently disable the battery (dead battery) and the battery should be discarded. To prevent this from happening, never leave the battery discharged for a long time. This will also help keep the battery healthier.

If you are not going to use the battery for a long time (many weeks) it is best that you charge it to about 40-50% before doing so and store it in a cool place (ideally in a fridge).

There exists a similar protection circuit inside the battery which prevents it from overcharging, which could also be detrimental. The circuit stops the charging process at a certain point, ensuring it is safe to leave the battery connected to the charger without fear of damaging the battery.

Memory effect

The batteries in an Eee do not exhibit any memory effect. ‘Memory effect’ is a term used to describe the loss of usable capacity in a NiCd battery caused by repeatedly recharging the battery without fully discharging it first. The batteries in an Eee, or any laptop in the last 15 years, are not NiCd batteries and do not exhibit this behavior.

Any reduction in capacity or voltage in the battery is due to wear down or natural aging which is not influenced by whether you fully discharge the battery before recharging. Indeed, fully discharging the battery before recharging may have a slight but insignificant negative effect on the battery due to increased wear.

Using External (home-brew or DVD player) Batteries

People have experimented building battery packs. Luckily the eeepc shares a battery consumption needs of many portable DVD players, and so the reports of using DVD player batteries may be more useful, reliable and quicker than following home brew solutions.

Please note that using batteries in your Eee that were not designed for an Eee (such as batteries from other devices) may cause permanent damage to the Eee or the battery if you do not know what you are doing.

Power-Saving Tips

The biggest built-in power drains that you as a user can affect are the screen, the wireless network, the CPU usage, and the Standby mode. The standby mode will drain a full battery in about 22 hours, so consider switching off the Eee PC rather than putting it in standby mode.

When the system is on, you can switch off the wireless network if you don’t use it. Turn down the screen brightness, have the screensaver switch off the screen aggressively, and don’t run too many processor-intensive stuff in the background. In the full desktop mode, try adding a Performance monitor applet to the task bar. (You can tweak it to take very little space). The bad news is that these things will only give you a very modest increase of battery life; see Power consumption of the Eee PC.

Here are some other tips:

Use the Fn+F3 to reduce screen brightness as low as possible (Use Fn+F4 if you need to increase it).
Use Fn+F2 to turn of the wireless network when you are not using it.
If you’re not using wired LAN, you could disable it in the BIOS. Remember to enable it before plugging in an ethernet cable, or you’ll wonder why you can’t access the ‘net!
If you’re not using the webcam, disable it in the BIOS.
Adjust screensaver settings.
To increase battery life from weardown-effect (see above), when using the EeePc, use it with the AC(/adaptor) and the battery removed as much as possible!
In the case of unplugging and storing the battery away for several months or more, first half charge the battery, and recharge about once or twice a year. If not recharged in a long time, battery might become dead. Its life can be extended by charging it only half-full and storing it in the fridge (see Wikipedia). Let it come back to room temperature before re-use, though, and check the charge state every few months.
Use the lower voltage, underclocked 630MHz mode
Use a USB flash drive rather than a USB optical drive
Use a USB flash drive rather than a USB hard drive
Avoid utilizing 3D graphics hardware either in games, screensavers or the desktop (especially Aero, Compiz or 3D screensavers).
If using Windows, activate a power saving mode such as “Max Battery”.