This depends on what you are using and what you are doing. Without heavy use (e.g. no use of PCMCIA slot and light use of CF) you should manage 8 hours. However this will only decrease with use of serial port (which reduces life by about 1.5 hours), PCMCIA card slot (which has been reported to reduce life to 3 hours), heavy use of Compact Flash. Increasing the brightness setting (via the screen component of the control panel) will lead to increased power consumption. I have not yet run low (unless deliberately) because I find I'm always plugging the machine in to the external power source. The battery is a Li-Ion rechargeable battery. This is a sealed, non-serviceable unit that houses three 3.6v graphite-type Li-Ion cells. These give a very steady energy output until depletion at which point they very suddenly become flat. This means unlike with the AA batteries the CF card, recording and playback of sounds will always work with this machine.

There is no memory with this type of battery, this means you can charge it up at any point in its power cycle and the total charging capacity will not be effected.

When charging the charging lights come on. One red which is stronger the lower the battery current, and one green which become brighter as the battery is charged. Note although the red light dims out completely this does not indicate a full charge (this requires 3 hours). Using the lights as indicators you will get a 75% charge. You should there leave the mains in despite the charge light state to fully charge the battery. This is because although it reaches its maximum voltage, the maximum power is not reached.

If not used the battery may run flat after 3 months. You should therefore charge at least once very 3 months even if you are not using the machine (although I can't see why this would happen!). You can buy spare batteries from the suppliers mentioned in 'where can I buy a psion Series 7?' . Caution should be taken when replacing the battery because if removed without care the machine can hard reset. I have had no expereince of this, but it has happened to some people.