Why is the battery meter reading on my Nikon D5000 not changing?

The battery meter on the screen is displaying three bars [the full amount], and doesn't seem to be changing despite the fact I'm using the camera a lot. I haven't charged it in about three days.

I took two 30-minute long exposure shots of the stars which should definitely have drained on the battery but it's still saying that it's full. What could have caused this problem? Could cold weather have done it? Everything else on the camera works fine.

Cold weather is more likely to really drain the battery. I think the battery meter is accurate

Your camera can take up to 510 images before you have to charge them overnight.

You may be used to P&S cameras where the number of shots are closer to 200 or so before you had to charge the battery.

Long exposures do not drain the battery, but leaving the camera in Live View will. The second and third most draining function of the camera is using the built-in flash and using the image review feature on.

Sometimes even if battery is near to exhaust point and your appliance can show that battery is full this is mostly in the event when battery has got some malfunctioning

My D3000 will read full until it's getting close to being out of power.It'll change down to one bar (white) and then only be good for another maybe 50 photos. It's probably just a stupid problem in Nikon's firmware.