"add rechargeable batteries" That would be an epic fail. Like most of us, I carried around a 4-pack of AAA for my calc (at least thats what the TI-81 took) an

"add rechargeable batteries" That would be an epic fail. Like most of us, I carried around a 4-pack of AAA for my calc (at least thats what the TI-81 took) and if the battery finally ran out during a test, no problem, 30 seconds later you're back on the air. Also the teachers sold batteries or you could bum them off a neighbor. With rechargeable, I guess you just fail? Also rechargables are carefully value engineered to fail after a couple years, so that would increase costs quite a bit. A school system that bought a couple TI84 a decade ago can keep on using them today with COTS walmart batteries, but sealed rechargables means they would have to keep buying them every couple years. With careful value engineering the mfgr could likely get the lifetime down to a bit over a year, and sell kids a new calc every single august for school. Note that these calcs, at least the TI-81, were not like smartphones. A set of batteries lasted at least a couple months even with some game playing. I wrote some text adventures and others wrote little arcade games and still we got over a month at a time. The -81 was extremely crude as a programming language even compared to 1980s home computer BASICs.