Li-On Batteries

Li-On Battery Do's and Don'ts

Here is a quick list of Do's and Don'ts for the care of your Li-On batteries.
When you receive a new NoteBook or Tablet PC, leave the battery to fully charge overnight.
·         Do Not - Expose the battery to excessive heat or cold (i.e. outside the range of 10-35 degrees Centigrade ambient).
Remember: Your battery is slowly degrading all the time, even if it is not used. Keeping your battery as cool as possible will slow down this degradation considerably.

Essential Li-On Information

Lithium-Ion batteries have a finite life, they slowly degrade from the day they are first made. The life of the battery will depend upon how you charge and discharge the battery and the temperature at which the battery is kept. A manufacturer will rate a Notebook battery to the point where it holds 50% of its original capacity.  At this point you should consider replacing the battery.
RM has been in consultation with one of the world's leading authorities on Lithium-Ion batteries, Isidor Buchmann, President and CEO of Cadex Electronics ( We are able to provide the following information to our customers about the best practices for the treatment of Lithium-Ion batteries, as used in many Notebooks and Tablet PCs.
How can I make my Lithium-Ion batteries last longer?
Lithium-Ion batteries are very different from Nickel-Cadmium (Ni-Cd) batteries and must be treated differently. Notebook batteries deliver an extremely high current (similar to a power hand tool) and so the batteries are stressed much more highly than a low-current battery (such as that used in a mobile phone).
Lithium-Ion batteries begin to degrade from the moment the battery cells are made by the battery cell manufacturer. This is due to a chemical reaction that gradually causes the internal impedance of the cells to increase and in time, and reduces the ability of the battery to deliver its charge. All chemical reactions are affected by heat. Each 10 degrees Centigrade rise in temperature will double the rate of this reaction. For this reason, it is very important to keep you battery as cool as possible at all times, especially when it is charging.
The other main factor that can drastically reduce your battery life, is if it is left in a fully discharged state for any length of time. If a Lithium-Ion battery becomes too 'flat' it will refuse to be charged up again (even though the battery cells are probably good). If this happens you will need a new battery. For this reason do not store the battery for more than a week or so in a fully discharged state.
Under ideal conditions, after just 1 year, a Lithium-Ion battery will probably hold about 80% of the original capacity of a new battery. Even if you keep your battery as cool as possible, it can only be expected to last for 2-3 years at the very most.  If a battery is often kept warm/hot, it may only hold around 50%-60% of its original charge after 1 year.

Using Notebooks (and Tablet PCs) in schools

Generally it is best for schools to keep Li-On batteries fully charged. You can top-up the charge as often as you like. During the school holidays it is best to ensure they are 50%-100% charged, as storing batteries in a discharged state can be permanently damaging. You should always switch off the chargers during school holidays and make sure the Notebooks are not left on.
The battery should not be allowed to get warm if it can possibly be avoided. For this reason it is recommended that you always switch off the AC adapters at weekends and during the holidays. RM recommends the use of a Mains Timer. These can be set so that the mains is on only during the day (say 9 am to 8 pm).  This will also ensure that where you store the Notebooks (e.g. in a cupboard or in a NoteBus), the batteries are kept as cool as possible.
If not using the Notebooks during the day, it is best to switch them off, because if you leave them on, they will get warm and this will shorten the battery life.

Charging a Lithium-Ion battery

Lithium-Ion batteries can be charged at any time, whether at a 90% charge level or only 10%. You should fully charge them if you are not going to use them for several days (do not leave them in a discharged state for more than a week or so).

How long will a Lithium-Ion battery last?

The biggest enemy of the Lithium-Ion battery is heat. You should ensure that when you charge and store your Notebooks or Tablet PCs, they are kept in a cool place with plenty of ventilation. A notebook may get quite hot during use, but is important that the battery itself does not get hot as this will shorten its useful life.
It should also be noted that Lithium-Ion batteries tend to 'die' rather suddenly when they have reached the end of their life, whilst NiMH batteries will slowly degrade when they are nearing the end of their useful life. As a Lithium-Ion battery is taken through more charge/discharge cycles, it will deteriorate much faster if mistreated (e.g. left charging for 2 months during the school holidays with inadequate ventilation), so that you may find a drastic reduction in capacity as the battery approaches the end of its useful life.
If a battery only lasts a few minutes, even though it is fully charged, this may be because it is no longer accepting charge. This can happen when a fully discharged battery is stored for several months. For this reason always charge your batteries to a least 50% charge if you are not going to recharge them for a few months. Once Lithium-Ion batteries have become fully discharged they cannot be recharged by normal methods.

Why isn't my battery lasting very long after only a few months of use?

Apart from the obvious reasons (it is too old or has been mistreated), the other reason may be in the way that you charge it. If the battery is never allowed to fully charge and then fully discharge, it will become 'uncalibrated'. You can prevent this by ensuring that every month or so, you fully charge and then fully discharge the battery. After fully recharging again, the battery will be recalibrated and it may now last longer before Windows shuts down.