Found a seller on ebay that offers two 3.6v saft AA lithium batteries for 5.95. Put in to a battery pack with a suitable connector, these will fit in to the head. Can anyone see a problem powering up the prime and secondary this way with these batteries? Typical meg packs are 5 times 1.5v or 2 times C Cell 3.6v packs and bought in the uk are about 30 quid each. The isc packs are about ten quid each plus postage and customs if bought from the US.