The T-38 had Lead-acid batteries when I was a student. Some years later, the Air Force converted them to NiCad.

Today?

Back to lead-acid, for about 10 years or more. I'm not sure if it was a thermal runaway issue, or the "sudden-death" nature of NiCads. (No warning they are about to fail).

Point is, sometimes engineering mistakes are made, and they have to be corrected....even if the correction is going back to the tried-n-true.