Most computers and electronic devices like Tablet PCs and UMPCs use Lithium Ion batteries. Lithium Ion (LiIon) batteries have some really compelling advantages that make the kind of small and lightweight gadgets that we have today possible. Lithium Ion batteries:

• Have a low weight to energy ratio
• Can be made in a variety of shapes and sizes
• Do not exhibit a memory effect (you don’t need to discharge them or run them down before charging again)

However, there are some disadvantages to having all this power…

What you should be aware of with Lithium Ion batteries:

• They have a minimum charge threshold - usually protected by the electronic controller on the battery-  and if they go below it they may be unrecoverable (i.e. dead).
• They lose capacity over time - A full battery will lose about 20% of its total capacity every year if stored at 25 degrees C. If fully charged it will lose 35% per year at 40 degrees C (laptops often get hotter than this!).
• They have a limited number of charge cycles* – usually between 500 – 1000.
• You should expect to replace them at some stage.

Tips for saving your Tablet PC or UMPC battery

The following tips will help you to keep your Lithium Ion battery running as long as possible. You might find that some of these tips are not that practical, but being aware of them will help you.

1. Store it at 30% – 40% charge (I.e. not full) - For example, if you’re heading away for a month and your not going to take your tablet, charge it to about half and put it somewhere cool.
2. Never leave your Tablet PC in your car, especially on a hot day – As detailed above, heat will greatly diminish the capacity of your lithium ion battery to hold a charge. Keep them cool as much as practically possible.
3. Remove the battery from the Tablet PC when you’re running on power constantly (I.e. if you’re mainly deskbound).
4. Unplug it! Let your Tablet PC run on battery as much as possible rather than keeping the battery in the unit fully charged.
5. Don’t leave a battery flat for long periods of time – If you do, it may discharge below the voltage threshold, and they don’t come back from that. The typical storage loss is 10% per month, so if you left a battery flat for a month or two or three, it may not recover.

Battery power is a critical component of your Tablet PC. Without your Lithium Ion you simply won’t be mobile anymore! So when choosing a Tablet PC you want to consider a couple of things about it’s batteries:

• How much do they cost? – Any decent Tablet PC or UMPC will outlive its battery! You absolutely will need to replace them at some stage
• How fast do they charge? – Some charge much faster than others
• How many will I need to keep? – If they charge faster you will probably need fewer batteries
• Will they continue to make the batteries? – Lithium Ion batteries do not store well as outlined above, so it is not a good idea to buy some for now with the intent of using them in future. You will want to be able to buy fresh new batteries in future.

* Charge cycle = 100% full discharge and recharge. So, if you discharge and recharge to say 60%, then back to full, then another 40%, then back to full you have reached 1 cycle.