Nikon Coolpix 990 - Manual (Page 17)

The Coolpix 990 uses four AA size batteries as its power source. I highly recommend
NiMH rechargeables as this camera like all digicams, eats alkaline batteries like candy.
At first I was a little concerned about the DC power input jack being on the front of the
camera. But after plugging the cable in that goes to my
Unity Digital ProPower pack I
was thrilled to see that it was a match made in heaven. There's still plenty of grip
surface left for your fingers and the angled plug makes the cable run straight down to
the bottom of the camera.