Every time I charge my battery, when I start my camera, it asks me to input the date and time.  Why? It's very annoying.

  • 3
    How long is the camera left without a battery?
    – Tetsujin
    Nov 25 '18 at 9:44

The Nikon D5100 uses a rechargeable internal clock battery. It should have enough charge to give you 3 months to charge the main battery. A main battery that is almost completely empty, should also have enough power left to keep the clock running for months or even years. There is probably a problem with your internal battery, or a contact to it.

The best option is to have it fixed, or to fix it yourself.

You can see the battery is step 7 on this site:

The battery is a MS518SE 3 Volt Lithium battery.


Most cameras have a capacitor or internal battery that keeps the clock and settings active while the battery is being changed. If the camera is left with a dead battery for a very long time, the capacitor or battery may become fully discharged and dysfunctional.

  • 1
    If you get a second battery (there some good brands that are much less expensive than original Nikon parts), you can just swap the batteries in the camera and charge the one you took out. The swap time will be too short to have the settings lost. Plus you have second battery for these occasions where you draw a lot of power (liveview, flash, etc...).
    – xenoid
    Nov 25 '18 at 8:28
  • 1
    Quickly switching batteries is worth trying, but may not work. I have an old camera that loses settings when the batteries are removed for even a fraction of a second. Something else to try is connecting the camera to USB while changing batteries.
    – xiota
    Nov 26 '18 at 11:46

There is usually an internal battery/capacitor that helps maintain small bits of information like date time and location. Most likely this battery is dead and causing you to re-enter the information. The D5100 is not really user serviceable and I wouldn't recommend changing this yourself. You can get yourself a battery grip and get a longer shooting period without having to re-enter this information on shoot days.

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