HP-50g Backup Battery

[SteveD]

How can I tell when my HP-50g Backup Battery (a CR2032) needs to be replaced (as opposed to my main batteries)?

The low battery annunciator, the ((.)) on the top line, and the accompanying "Low Battery(s)" message are non-specific and the none of the HP-50g manuals specify whether they refer to just the main batteries (4x AAA) being low or that either the main batteries or the backup battery is low.

If the low battery warnings come on when the backup battery is the one that is low (without mentioning which batteries it's talking about), I think it's talking about the 4 AAA main batteries which are the batteries most likely to be low, and I remove my main batteries to replace them, then I would have no good batteries in my calculator & lose everything in memory.