A friend now owns my trusty Canon SX230HS camera, but, given the restrictions on shipping lithium batteries, we agreed there was no point in transferring ownership of my nearly dead batteries.
For completeness, their final state:
The original Canon OEM battery (orange curve) looms above all the offerings from various Amazon sellers.
Searching for NB-5L will excavate many posts relating my misadventures, tests, and test fixtures:
Maybe I should build an astable multivibrator with a slip-in battery compartment.
The Smell of Molten Projects in the Morning 