I first started operating portable as part of the Summits on the Air (SOTA) program in March 2013. At that time I used the supplied internal batteries for the Yaesu FT-817nd, which comprises eight (8) NiMH AA cells in a shrink wrapped package, with the rated capacity of the pack being 1400mAh. NiMH cells have a nominal voltage of 1.2V, so the total being 9.6V.
I then started using Sealed Lead Acid batteries (SLAB), a 12 volt 4Ah SLAB battery to be precise. I purchased these from the local Battery World Outlet. These were a little heavy, weighing in at 1.75 kg. That was ok for the easy summits, but many of the summits I was activating required a walk to the top, so reducing the weight in the backpack was a consideration.
My next purchase was a commercially made power pack by Matson, which in essence is two 22 Ah SLAB batteries. This is an excellent option for park activating and easy walk up summits. But being very heavy it was not an option for climbing.
So I then purchased some LiFePO4 batteries from Hobbyking. I have two (2) LiFePo4 (lithium iron phosphate) batteries. One being a 13.2 v 4.2 Ah (4200 mAh) and the other being a 13.2 v 8.4 Ah (8400 mAh). I purchased these through HobbyKing….. http://www.hobbyking.com/hobbyking/store/index.asp The 4.2 Ah LiFePO4 weights just 558 grams. Much lighter than the 1.75 kg of the 12V 4Ah SLAB. The 8.2 Ah LiFePO4 weights 1.026 kg. Still lighter than the SLAB.
LiFePO batteries are not to be confused with LIPO batteries (lithium polymer). LIPO's are widely used in the world of radio controlled aircraft and radio controlled cars. However, they need careful handling and the voltages are not directly useable for amateur radio transceivers.