every battery has a built in chip wich masures all the values. correct me if im wrong. Every battery is different.

I had 4 n900's in my hands in the past, and all of them felt different, slided different etc etc. So products even when they are produced exactly the same are still different.

When i read about the backup power i remebered a test i did back in my teenager time. i once called a friend with my nokia with an emty battery. it died instantly, i fired the phone back up and called 9-1-1 emergency (112 in holland) for some reason the phone did not die. so i guess that the phone then even recognised the emergency and did not shutdown itself. i havent tested it on the n900 though.

But when the n900 is saying 0% then offcourse its not 0% in the battery. there is always a safety in it . its very bad for a battery to be drained 100% it could even damage the battery.