I also bought another pair of Wasabi Power NP-BX1 batteries to see if they were as good as before:
The red traces are the original units (AB, January 2014), the blue traces are the next three batteries (CDE, October 2014), the purple traces are the new pair (FG, October 2015), and the green trace is the OEM Sony battery, all tested when more-or-less new.
So, about the same as before, not as good as the first pair.
That may show a year on the warehouse shelf doesn’t affect lithium batteries very much, because the date codes atop the batteries, labeled in order of arrival:
- AB = BMK20
- CDE = BNI18
- FG = BNI13
Assuming my interpretation of the date codes is correct, the last two digits indicate the day of manufacture: the most recent two batteries (F and G, arrived a few days ago) are five days older than the previous three (C, D, and E, arrived Oct 2014); all five were manufactured in September 2014, a bit over a year ago. The first two were built in November 2013.
The problem with lithium batteries is that no two devices use the same battery, even when the batteries are functionally identical, so distributors must stock an acre of separate items, each of which move pathetically few units. Perhaps the top ten items make up for the rest?