My D600 will not boot up unless the power cord is plugged in. Is there some switch that I hit by mistake? Can this be corrected? I guess basically it doesnt work on the battery unesss it is plugged in but the power shows 100 % for the battery
Thanks for the asssistance

Can you try another battery to rule out the battery or motherboard is the issue?

The real check you want to do is just this. Does the system run on the battery that it doesn't boot on. Obviously you can't boot from the battery but if it runs from that same battery then its a motherboard problem. Also, note that your machine shouldn't be able to resume from standby on battery either. This problem has happened to many other Dell users including myself (twice). The new motherboard completely fixes this issue.

Note: Your machine is probably still able to boot from battery. It does so very infrequently; about once in every 20-50 tries. Obviously, this is still considered unusable to most people.

Dell has designed the "smart battery" system into it's laptops. If the system fails to communicate with the battery at startup, BIOS implementation might prevent startup. What BIOS revision you're using and is it the latest available?

Is the battery genuine DELL? Can the battery type be identified in Windows power options? Click on the battery and it shows manufacturer and type. BIOS setup also shows this info.

Read about the DELL laptop battery charging system.