I sent the SterlingTek batteries back and requested a refund. They wouldn't answer my question if they had changed suppliers.

I ordered a Duracell 511 battery that has a 3 year replacement warranty and will see how it performs. It costs $25.88; more than the SterlingTek, but less than a Canon replacement. Will keep you updated. I initially saw the battery at www.duracelldirect.com (same price as Wal-Mart) but ordered it through Wal-Mart who drop ships it from wholesaler BatteryBiz. I am covering a bridal shower Saturday and wanted the battery before then. Expedited shipping from Duracelldirect was $30.00 and expedited shipping from Wal-Mart was $7.00. I ordered the battery Sunday night and got it today (Wednesday).

Duracelldirect had this info on their website which I thought was interesting:

Break In New Batteries: New batteries come in a discharged condition and must be fully charged before use. It is recommended that you fully charge and discharge the new battery two to four times to allow it to reach its maximum rated capacity.