Lithium (coin cell) backup battery

[Jonathan Busby]

(11-20-2021 06:39 PM)Jonathan Busby Wrote:  

(11-20-2021 06:26 PM)SEasterling Wrote:  Thanks for the replies and sorry for my ignorance using the battery type too loosely. I should have specified lithium coin cell (3V, 2032) and was inquiring exclusively to HP graphing calculators. (I didn’t realize there was a large TI following here since it’s been a long time since I was active on this forum.). But specifically, I was wondering if HP had ever used a “lithium coin cell” for memory backup on any of the 48 series models (e.g., 48G+ or late-production 48GX) before discontinuing production in Indonesia. I know that my 49G+ and 50G models have this extra battery, but didn’t know if HP started doing it on the 48 just prior to ending that series. I know that none of the 48S, SX, G, G+, or GX models I’ve owned didn’t have them, but I may not have had late production models. Thanks.

To the best of my knowledge, none of the Saturn-based S/SX or G/GX models ever used a backup battery, instead, they used a capacitor to maintain the SRAM contents when changing the batteries.

Regards,

Jonathan

I own a late production Indonesian HP48GX and it has no backup battery. I bought it around 2003 from Fry's just before HP discontinued the HP48G series. Seeing that HP had no intention of continuing production of their Saturn-based calcs, it would have been illogical for them to spend money to rework the PCB and case for a backup battery. Reworking the PCB wouldn't have been a big deal technically but there's the problem of really no more pins available on the Yorke SoC to detect a backup battery low battery condition. Reworking the case would have been harder to allow the user to change the battery -- HP really had no incentive to do this as they were discontinuing their Saturn-based calcs.

Regards,

Jonathan