We use a NiCad. That's not unusual, although nowadays people are buying Lead acid batteries because they have more juice, give cooler starts and after a number of years you just chuck em. They are cheap and don't have to be cycled etc.. ie no maintenance. We haven't gone that route because we operate in -40 degrees occasionally and we are not sure how that will effect them. Leave well enough alone.

The NiCad problem of years ago was solved by improved quality of plates. They don't warp as easily at high temperature and also better venting for the batteries has made this "Runaway Battery" problem history.

Actually full size aircraft don't get new technologies until they are old technologies. Our instruments although up to date are old news say compared to the computer world. The idea being that let the technologies settle down and we take the rock solid ones.

Can you imagine having Microsoft Word running an aircraft!!! Scary! Uh sorry folks but our instruments just crashed.