Updated 19 March 2006
I purchased my first digital camera, a Canon D30, in December 2001.
I later upgraded to a 20D, bought my wife a 300D, and handed down
the D30 to my daughter for her nascent photography business. My
daughter takes more exposures by far than the rest of us. She has
complained lately than many of the dozen or so batteries in our
pool (shared in common among the three cameras) are not holding up.
After some Internet research, I learned that Lithium-ion batteries
like the BP511 wear out after a few years. I decided to build a
text fixture to characterize our collection of batteries. I also
bought four new batteries from SterlingTek, anticipating that many
of our current batteries would prove worn out.
NOTE: Test runs prior to the evening of 14 March 2006 terminated on
a battery voltage of 5.2 V. This caused the underdischarge protection
circuit to trip on one battery. Those earlier discharge curves
indicate a negligible amount of capacity between 6.0 and 5.2 V.
Battery Description Purchased Nominal Measured Plot 1 SterlingTek 3/2006 1800 mAh 1225 mAh 1.pdf 2 SterlingTek 3/2006 1800 mAh 1221 mAh 2.pdf 3 SterlingTek 3/2006 1800 mAh 1149 mAh 3.pdf 4 SterlingTek 3/2006 1800 mAh 1274 mAh 4.pdf 5 SterlingTek 11/2004 1300 mAh 1101 mAh 5.pdf 6 Canon BP511 ? 1100 mAh 420 mAh 6.pdf RECYCLED 7 Canon BP511 ? 1100 mAh 539 mAh 7.pdf RECYCLED 8 Canon BP511 ? 1100 mAh 780 mAh 8.pdf 9 Polaroid PR511L ca. 2002 1100 mAh 479 mAh 9.pdf RECYCLED 10 Polaroid PR511L ca. 2002 1100 mAh 866 mAh 10.pdf 11 Polaroid PR511L ca. 2002 1100 mAh 867 mAh 11.pdf 12 SterlingTek 11/2004 1300 mAh 1118 mAh 12.pdf DONATED 13 Canon BP511A 11/2004 1390 mAh 1257 mAh 13.pdf 14 Canon BP511 ? 1100 mAh 977 mAh 14.pdf 15 SterlingTek 11/2004 1300 mAh 1127 mAh 15.pdf DONATED 16 SterlingTek 11/2004 1300 mAh 999 mAh 16.pdf 17 Polaroid PR511L ca. 2002 1100 mAh 380 mAh 17.pdf RECYCLED 18 SterlingTek 4/2006 1800 mAh 1347 mAh 18.pdf 19 SterlingTek 4/2006 1800 mAh 1359 mAh 19.pdf 20 SterlingTek 4/2006 1800 mAh 1370 mAh 20.pdf 21 SterlingTek 4/2006 1800 mAh 1351 mAh 21.pdf 22 SterlingTek 4/2006 1800 mAh 1355 mAh 22.pdf 23 SterlingTek 4/2006 1800 mAh 1291 mAh 23.pdf 24 Canon BP511 ? 1100 mAh 998 mAh 24.pdf
NOTE: The good batteries all produce a fairly flat discharge curve with
a sharp knee at the end. The bad batteries produce a discharge curve with
a steady slope, suggesting a high internal resistance. This high internal
resistance is said to be caused by internal corrosion, and is the usual
failure mode for Lithium-ion batteries.
NOTE: Some have interpreted this exercise as a slam on SterlingTek.
Not so--I have been very satisfied with their batteries. They are at least
as good as Canon originals. Sadly, most capacity claims from most battery
vendors are exaggerated. Caveat emptor!