Nikon D300 User Manual page 479

This Battery info screen is just for information so there's
nothing to set. When you've finished examining your
camera's Battery info, just press the OK button to exit.
The D300(S) goes a step farther than most cameras. Not only
does it keep you informed of the amount of "charge" left in
your battery, it also lets you know how much "life" is left.
After some time, all batteries weaken and won't hold a full
charge. The Battery age/Charging life meter will tell you
when the battery needs to be completely replaced. It shows
five stages of battery life, from 0–4, so that you'll be prepared
for replacement before your battery gets too old to be of
many-shot use.
My Recommendation: In my opinion, it's important to use
Nikon brand batteries in your D300(S) so that they will work
properly with the camera. Aftermarket batteries may not
charge correctly in the D300(S) battery charger. In addition,
they may not report correct Battery age/Charging life
information.
There may be an aftermarket brand that works correctly, but
I've not found it personally. Instead, I choose to use the
batteries designed by Nikon to work with this camera. I am a
bit afraid to trust a camera that costs this much to a cheap
aftermarket battery of unknown origin. In Figure 5-26 you'll
see a picture of the top and bottom of a genuine, gray-colored
Li-ion Nikon EN-EL3e battery. See the 3D Nikon hologram
on the top right of image 2?
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