Why my Nikon d3000 doesnt work with completely charged battery?

I dont know what you did or didnt do send it to nikon they will tell younwhat the problem is how much it cost to fix and how long it takes to fix then they send it back to you if its under their warranty they fix it free.

First off, have you dropped or otherwise impacted the camera, taken it to a sandy area, or spilled a sticky drink or water on it?

If dropped, then there is a flex under the bottom on the rewind side (or where it used to be) that can be broken by impact. Nikon does not sell this part, it would have to go to Nikon.

Check the mirror. Sometimes it is pushed to the left by impact and lodges against rather than on the stop. You should be able to gently lift the mirror. If the mirror is stuck, you may be able to gently lift it up and free it until it once again rests on the top of the stop.

There were a lot of defective main boards for this model. If you have consistently had problems, then send it to Nikon. I believe there have been 3 modifications of this board to solve a non-power problem.

How old are your batteries? If your batteries are more than a year old, especially if they are non-Nikon batteries, they may have gone bad and not be able to store enough amperage to operate the camera.