When I connect my phone to my laptop it automatically starts charging, however I would just like to use it in PC Suite Mode. Any ideas?

Remove the battery? Only plug it in when it's fully charged perhaps?

This is an unusual request, why is this important to you?

It is important to me because it drains my laptops battery.. All I need is to use the PC Suite mode, I don't want to charge my N900, since the battery is charged enough for me.

It is an unusual request to take out the battery when connecting the phone to a laptop. Thats a good one. You made my day!

Let us know if this works.

Cheers!

The N900 can't be powered on when it has no battery inserted without extra hack and good timing (forgot what post it was but a guy has proved that the N900 can be powered without battery for a few seconds when the charger is plugged)
For your question, you can try in terminal as root:
stop mce
Then plug the N900 in your PC, but I'm not sure that the USB system will work without mce.

@Dgonik what you are trying could be considered a hack.

The device is not intended to be used as you want. If you plug it in, it will start charging, AFAIK.

I know a hackish solution:
- go to a x terminal console, and type
- sudo gainroot
- stop bme

That way, you will be stopping the glorious Battery Management Entity, so then you could plug in your phone to the pc and it will not start charging.

I'm not sure about the secondary effects. BME is an important part of the phone.

remember to turn it on manually later.

I cant offer help, just wanted to add that I dont find this an unusual request - many windows mobile devices have it as an option in the settings.

Still doesn't make the OS any good though