Why have these batteries lasted so long?

I have a new hobby collecting old TI calculators with LED displays. Even with the battery packs rebuilt with new NiCads I only get a few hours use out of a charge, just like in ancient times. Contrast this with my regular, “daily driver” calculator, a Casio with an LCD display, no solar panel, permanent memory that I assume needs regular refreshment, and its original, un-rechargeable batteries that I bought in 1986! And these batteries don’t look like anything fancy, like alkalines. They appear to be plain ol’ carbon cells except they still, after 18-1/2 years, hold a charge and haven’t leaked. Why have they lasted so long? I know LCDs draw less current than LEDs (considerably less, it would appear) but at best when I bought the calculator I expected to replace the batteries in about a year. To have them last this long was inconceivable.

I don’t know either, but I too have a Casio® calculator I bought in 1983. It is battery and solar. Its still going strong even in low light so the battery is still good. It seems they didn’t expect you to ever change the battery in it either. I had to take the whole thing apart to get to it. ( Well, actually, I just take things apart.)

Are you sure they are in fact zinc-carbon cells? What size are they? I don’t think that carbon batteries have that long of a shelf life let alone useful life.

Takes me back. I got a TI-59 after I graduated from high school. Something like half a kilobyte of memory IIRC and a magnetic card reader for storing programs. Battery sucking monster.

Besides the switch from LED to LCD displays, integrated circuits moved from PMOS and NMOS to CMOS. CMOS circuits use far less power than PMOS or NMOS circuits. They only draw a noticeable amount of current when they switch states. In a device like a calculator, that spends 99% of its time in an idle state, the power savings are enormous.

Ain’t THAT the truth! It is, in fact, a TI-59 that triggered this. I put in some 800MAH phone batteries which help. I didn’t want to experiment with NiMHs right off thanks to warnings I received here–make sure the bastitch works before getting too creative–but I think I will try them with the next.