So as an experiment, I've replaced the battery in a MV1FZ with a 0.47F 5v super-capacitor (I have larger 5F ones, but they're chonky and this little one fits under the cartridge cowl). After leaving it running for awhile, I left it overnight and it's retained the calendar and soft-dip settings. Which would seem to be a positive indicator. But I'm not sure how long it would take to fully "charge", how long that charge would last powered off or even how long it takes for the backup RAM to clear when there's no power given that it retained data during the battery removal and replacement. I had previously tried to run the numbers, but I had to fudge too many of the variables such as voltage delta and amperage draw that it was kind of meaningless (and I don't math gud). So, opening this up for discussion & comments.