Here in the first picture is the battery that I use the most it is the Tenergy (not to be confused with the Turnigy batteries) 2000 mah 6volt Nimh. I buy them in bulk anywhere from five to ten at a time and these are what I use in the vast majority of my fleet and they have proven to be very robust.

I Absolutely do not use four cell Nimh for any 2.4 system and I believe the five cells types offer a much better safety margin. The only exception to this is I do have a few controlline airplanes that I do use fourcell types with 2.4 but those airplanes most have only one or two small servos and are never more than sixty feet away

Now I do use other technologies where its appropriate for instance I use two cell Life's for my diesel fuel pump pictured and the are ideal for pumping large quantities of fuel. The last picture is a three cell Life that supplies my turbines pumps and computer.

Heck I even use fourcell Lipo's for my daily starter having experimented with just about every possible type over the years and perhaps some might remember the many variations I have posted and pictured over the years.

John