A typical scenario is that you have been using a notebook or tablet PC on the battery for several months and you notice that it does not last as long on a single full charge as it used to.

For instance, when first purchased, the system lasted for two hours on a fully charged battery, but after three months it only seems to last for one hour.

The cause may be one of the following:

• There is an issue with the mains supply.
• The AC adaptor is not the correct type or is faulty.
• The battery requires re-calibration.
• The battery is past its useful life, possibly because it has been kept at a high temperature for extended periods.
• The battery, system or charging circuit/AC adaptor is faulty.

It is essential to carry out the following procedure in the order listed.

1.  Check supply

1. Use a known working AC mains lead and AC adaptor of the same type (if you have one).
2. Connect the AC adaptor to a mains wall socket that you know is working (eg if you normally charge from an RM NoteBus, remove the adaptor from the RM NoteBus and use a wall socket instead).
3. Switch the system on and check that the power icon at the bottom right of the system has a 'mains plug' symbol and that is says 'On AC Power' or 'Charging' when the pointer hovers over it.

2.  Check the Power Scheme configuration

To check the configuration of the Power Scheme of a system, look at the Control Panel, Performance and Maintenance, Power Options and check that you have not set the 'Running On Batteries' settings to a short time (eg 20 minutes). This would cause the system to enter standby mode after being idle for 20 minutes. Similarly, if you have a 'System hibernates' option, check that this is not set for a short time. This may give the appearance that the battery is not lasting very long, but in fact the system is simply switching off after a set period of idleness.

Tip: To give slightly better battery times, use the Max Battery or Presentation Schemes (note: this may also reduce performance on some systems).

3.  Recalibrate the Smart Battery

1. Check that the system is on AC power (see 1. above).
2. Switch off the system.
3. Leave the system overnight (eight hours) to charge.
4. Switch on the system and check that the system is still on AC power (see above).
5. In Control Panel, Performance and Maintenance, Power Options, and change the Power Scheme to Always On. Then change the 'Running on Batteries' settings to all say 'Never' and click on 'OK'.
6. Click on the Power Meter tab, and check that the battery is at 100%.
7. Now remove the AC adaptor plug and switch off the AC adaptor power at the mains supply.
8. Time how long the system remains powered. You can use a utility to log the time to the hard disk at regular intervals (see Other Useful Articles below).
9. After the system has switched itself off (usually by a self-controlled 'Shutdown'), connect the AC adaptor again and switch on the power to recharge the battery.
10. Leave for eight hours to fully recharge.

If step 8 above took several hours, then the battery required calibration, and this procedure should have fixed the problem.

If step 8 still only lasted for a short time (eg 30 minutes), you may have a faulty or old battery, so go to the next test below.

4.  Try another battery

If you have another system of the same type that seems to have good battery life, swap over the batteries. If the 'good' system now has a short battery life and the 'bad' system now has a much longer battery life, this indicates that the battery has a problem.

However, if the short battery life problem seems to stay with the original system, this indicates that the system may have an incorrect configuration.

Please note: As Lithium Ion batteries have a finite life, they usually have a limited warranty (eg a notebook with a one year warranty may have a six month battery warranty). Please check the warranty terms and conditions of your system.

Notebook and tablet PC batteries are usually the Smart Lithium-Ion type. They usually include a small micro-controller unit which can predict how long the battery is going to last. This prediction feature is necessary as without it, it would be very difficult to know when the battery is about to run out of charge.

If you consistently use the system for only an hour or so on the battery, and then connect it to the AC adaptor to recharge it, over the period of a few months the battery will 'lose track' of how much charge it really holds.

In this case it may report to Windows that it is about to run out of power, when in fact the battery has plenty of charge left. Windows will try to shut down if the battery reports low power and so your system may shut down prematurely, even though there is still charge remaining in the battery.

Battery calibration works by allowing the Smart battery micro-controller to re-calculate the length of time that a battery will last for. All you need to do is to ensure that the system goes from a fully charged state to a fully discharged state. This is done by simply ensuring the system stays on for as long as the battery will last.

Battery calibration does not extend the battery discharge time. This feature calibrates the battery so that it shows the remaining charge accurately.

Some notebooks have a battery calibration feature in the BIOS settings menu - consult the paper or on-line manual that accompanied your system for details.

When using the BatCal.exe calibration assistance utility, you may see the following message:

'The previous run lasted for XXX minutes before the battery ran out of charge.
Note: This time is not an accurate measure of battery life, to do this, you need to run a BatteryMark test after calibrating the battery.'

This message simply means that Bat-Cal is not a battery life test tool and is not designed to give a meaningful measure of how long a notebook will last on a fully charged battery.

Battery benchmark programs (such as BatteryMark) simulate the use given to the processor, memory and various other parts by an average 'real' user over a period of time. For instance, whilst typing in a text application, the hard disk and CD-ROM would be powered down and the CPU would be running quite slowly, but whilst performing calculations on a hard disk database or displaying DVD video movies, the system will be working quite hard. BatteryMark is an accepted benchmark program for measuring the 'battery life' of a notebook by simulating a range of these different activities.

For instance, on a brand new system:

• If using a word processor, the batteries may last for three hours.
• If watching a DVD movie from a DVD player, the batteries may only last for one hour and 45 minutes.
• BatteryMark may give a result of two hours and 15 minutes.

Bat_Cal.exe does not produce results that can be compared with BatteryMark or any other battery benchmark program.

You can however, use Bat_Cal to compare batteries by using the same notebook but replacing the battery with another each time you run Bat_Cal. You must remember to keep the display brightness, power saving settings and all other factors constant on each test run.

Any battery has a finite life span no matter what device it powers. Rechargeable batteries are no different from normal batteries with the exception that they can be recharged a finite number of times. Under normal use rechargeable batteries have a usable life of between 250-500 recharge cycles (depending on the type used).

Lithium-Ion batteries chemically degrade over time and with temperature. As soon as the battery cells are manufactured the 'clock is ticking'. The length of time your battery lasts will depend on how well you treat it (ie keep it cool and never leave it in a discharged state for months at a time).

Always keep notebooks and tablet PCs as cool as possible and store at about 50% charge level or more. A battery kept at 40°C in direct sunlight will deteriorate much faster than one kept at 20°C in a cool room. For instance, even if you do not use the battery, if it is stored fully charged for one year at 40°C it will only have a 65% capacity at the end of that year. That is, after one year it will only last 65% as long as it did when it was new! However, if you store it at a 40% charge level at 25°C or less for one year, it will have a 96% capacity by the end of the year - ie as good as new!

Always ensure there is adequate ventilation around a notebook and avoid placing them in a confined space when they are charging, unless adequate ventilation can be ensured. This is because the AC adaptors will discharge heat whilst they are on, and this will warm up the air around the notebook battery and thus the notebook battery itself. If you have several notebooks or tablet PCs and their AC adaptors in a confined space, the batteries will be kept warm for long periods of time. In particular, placing the AC adaptor on top of, or in close proximity to, the battery compartment when in use or charging will severely affect the useful battery life and they may only last six months.

If a Lithium-Ion battery is always kept cool, it should last for several years. If it is kept at a warm temperature for most of its life, it will not last much longer than one year. This is why most manufacturers will only warranty their batteries for periods of between three months and one year (maximum).

For the same reason, never buy a spare battery for use later on in the year or next year. Lithium-Ion batteries start to degrade as soon as they are made. So only buy a fresh battery at the time that you need to use it.

When storing notebooks for long periods (for six months or more for example), charge the battery (ideally to 50% or more, but never less than 40%) and then remove it from the notebook before storing in a cool place (but not below five degrees entigrade). This process will reduce battery degradation while it is stored.

Battery calibration does not recondition the battery cells but merely allows the notebook 'Smart' circuitry to accurately predict how much charge the battery is holding at any time. Battery calibration 'teaches' the Smart battery so that it can assess how long the battery will last if fully charged - it will then show the amount of remaining charge more accurately on future charges.

A battery that has gone out of calibration may, for example, show 90% charge remaining when there is, in fact, less charge actually remaining. This may show itself when a notebook suddenly powers down while it reports a reasonable percentage of capacity still remaining. Alternatively, the Windows battery power meter may show hardly any charge remaining after only say 1.5 hours of use, but the battery is only six months old, was fully charged and used to last much longer a few months previously.

If you are unsure how to recalibrate your battery, the BatCal utility below will guide you through the steps you need to take. If you are not going to use the notebook, you can use the Fast Discharge option so that the charge will be used up quickly. If you wish to use the notebook during the battery discharge sequence, use the Slow Discharge option (or simply Exit the utility). This utility can be used on any tablet PC or notebook and simply guides you through a full charge - full discharge - full charge cycle.