Batteries:
I find that the only reliable battery power sources for this monitor- until the rear-mount battery accessory is available- would be either very recently charged AA’s or lithium AA’s.
The tech rep from Marshall in El Segundo, CA has shown me a prototype of the upcoming accessory, one version of which will accept the battery for my D300s (EN-EL 3a).
I experimented with rechargeables over a period of several days and they seem to lose enough power in approx 24 hr that they don’t run this unit well, or don’t allow startup at all. Lithiums seem excellent, especially nice because of light weight.
HDMI Live view issues:
Unfortunately, the Coolpix S9100 apparently doesn’t allow LV feed to an external monitor. The D5100 apparently doesn’t allow LV feed while in 1080p/ 30FPS mode, although it works well in 1080p/24 FPS mode. Both cameras allow LV feed at all lower resolutions, such as 720 HD.
Therefore, the most obvious workflow would be to use the D5100 ‘s articulated monitor or a SD monitor for that mode. The S9100 works well on a slider or tripod.