HP-16C current consumption

[Ardvan]

Don't forget about the self discharge of these rechargeable batteries.

The specification sheet says: Charge Retention at 20C: 90%
So your rechargeable batterie looses 10% of its energy per month in addition to the current your calculator will need.

If you use the calculator regularly then this will work. If you leave the calculator off for many months this will not work, because then the calculator will probably be discharged when you need it.