When I ordered the Cree LED with 9V forward voltage I calculated a runtime of about 4 hours. I couldn’t check the actual voltages of the 9V block lithium ion batteries and ordered multiples with 680 mAh. Actually this kind of batteries will not have the 9 V :/ . Fully charged they have only 8.4 V. This is much too low for this array. The LEDs will only glow a little bit but for a very long time. The NiMH can help with a higher voltage of about 9.6V. The larges battery I could found was with 270 mAh. This gives you 1 hour of high lighting and one hour medium lighting. So what we will need is an LED array with a lower forward voltage. I checked and found this:

http://www.digikey.de/product-detail/de/NT-42D0-0426/521-1039-6-ND/1154195

This type of array fits with 7.6 V forward voltage but the efficiency is much lower than with the Cree. It doubles your capacity and halves the efficiency. Sound wired but that’s what I’m expecting with the the Lamina LED and the 8.4 Li-ion batteries.

http://www.dx.com/p/mp-rechargeable-680mah-9v-6f22-li-ion-battery-for-microphone-remote-control-more-silver-183353

Will this work as Beamboarder?!