I have some old Blonder Tongue BSTA spectrum analyzers that have NiCad battery packs consisting of ten 2200mAh cells plus an on-board charger. I tested three of those packs and get about one hour of use out of each of them with the screen set at full brightness. I figured that since they were a decade old, their capacity might have declined a little, so I bought ten 2700mAh NiMH cells from batteriesplus and soldered them into a pack, but am sad to observe that that pack runs my meter for about the same duration as the old ones. More recently, I bought some 6000mAh sub C cells from China and I just tested those today, yet in spite of them claiming to have more than twice the charge capacity of my other NiCads and NiMH cells, they, too, only sustained the meter for about an hour. They can be had from China for about $16 for ten cells with tabs, or you can get them shipped from the USA for about $25. http://www.ebay.com/itm/10x-Sub-C-S...US_Rechargeable_Batteries&hash=item2c6f052e1a . Needless to say, I am very disappointed in them Three weeks ago, I ordered ten 9500mAh C cells for $25 and ten 11000mAh D cells for $33 from China, without tabs, which is a minor nuisance to deal with because it is difficult to solder the negative wires as the mass of the cell sinks away the heat. I own a small arc welder that I have never used, so it looks like attaching tabs to these will be one of my first projects. Yesterday, the 11000mAh D cells arrived but curiously the C cells did not, even though the delivery notice said they did. The D cells don't fit into the battery pack compartment, but I'd be willing to make them fit if they got me appreciably more running time. I have more faith in them than in the 6000mAh I tried because I am confident that "bigger is better". The D cells each weigh twice as much as the sub C cells.