T61 Standby While Charging the Battery Question

[rubbish84]

I have a question regarding my new T61.

I have recently noticed that while charging the battery, if I leave the screen open and allow the computer to sit idle, it will not enter standby mode even though the power managment settings are set to standby after 20 mins when connected to wall power.

If I shut the screen while charging the battery it will enter standby with no problems.

Does anyone know why this would happen and if there is anything I can do to rectify the problem?

I'm currently running windows XP pro.

Any imput would be appreciated.

Thanks,