Nikon D300 Complete Manual page 100

Microdrives are more efficient than older versions, but still
use more power than static cards). During write
operations, a Microdrive takes longer to write the same
amount of data than a solid-state card, increasing power
consumption. In short, using a Microdrive results in
shorter battery life than using a solid-state CompactFlash
card (when measured in number of shots per battery
charge).
• Cold can appear to impact apparent battery life. Lithium-
Ion batteries have pretty good cold weather
performance—I'd be surprised if you see any differences
down to freezing temperatures—but they still will have a
tendency to produce power for shorter periods in
extremely cold conditions. If you must use the camera in
sub-zero temperatures, carry a fully charged backup
battery with you and keep that in a warm place (some
outdoor apparel has inside pockets for just this purpose).
As performance drops on the battery in use, swap it with
the warm one.
Cold doesn't actually "drain" a battery; it's the change in
internal resistance at low temperatures that causes
reduced function. So, once the replaced battery is again
warm, it functions normally. You can usually juggle two
EN-EL3e batteries this way and get the full number of
expected exposures from each.
• Fully charge your batteries. When the charger indicates
the battery is fully charged, it may not be. I generally
leave my battery in for a short time after the charger
indicates that the battery is charged. The test: if the battery
is cool to the touch and the MH-18a light is in a steady on
state, the battery is fully charged.
• 5% is about the point where you definitely want to
change batteries. It is okay to ignore the battery level right
down to about the 5% mark without any risk of losing the
next picture (this is for a single EN-EL3e battery; users of
two EN-EL3e batteries (one in the MB-D10 and one in the
camera can let the first battery run down completely but
Thom Hogan's Complete Guide to the Nikon D300
V1.02
Page 100