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.
Huh…
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?
The Smell of Molten Projects in the Morning 
I was recently looking for batteries for my sweetie’s older phone (this will be its third set). OEM ones simply aren’t available (although many sketchy eBay sellers claim to sell such), so it boils down to a choice of which Chinese reseller to go with. There seem to be three price points: $7-9 “new OEM” (probably garbage), $14-19 aftermarket/third party, and $28-35 aftermarket/third party. We went for the middle ground.
Interestingly, Nikon has been using the same EL-14 for several years now, across a wide range of cameræ. We’ve accumulated several of them, along with matching chargers. However, Nikon’s newest offerings use the EL-14A version, which is the same physically, but with more capacity. Both kinds work in all the cameræ, but the older ones will give less usage with the higher-capacity unit (there’s a firmware update available to fix this). I’m a little curious as to why that is.
From the brief description I saw, that battery includes a coulomb counter measuring incoming vs. outgoing charge; it even requires occasional recalibration (probably a full discharge-charge cycle). I betcha the original battery capacity fit neatly into a fixed-width field that can’t quite hold the higher capacity…