Having had the weaker of the two surviving STK batteries die 36 minutes into a ride, I tested them all:
The X axis shows W·h, rather than the usual A·h, because that seems more useful in a world of constant-power supplies.
The test current is now 1 A, rather than the previous 500 mA, to more closely match the camera’s actual load. The CBA tester doesn’t have a constant-power mode; I think that doesn’t make much practical difference.
The orange curve (STK D) is the failed battery, ending after 1.4 W·h. At an average 3.2-ish V, that’s 26 minutes, which is close enough to the actual run time, given the different current.
The red curve (STK C) is the sole STK battery of the original four from last November that actually worked.
The upper two curves come from the mostly unused Wasabi batteries (F and G), also from November. They have lost a bit of their capacity, but show the highest voltage out toward the end, so that’s good.
The black curve is the lightly used Sony OEM battery that came with the camera. Although it has about the same ultimate capacity as the other three “good” batteries, the voltage depression suggests it’ll trip out early.
The others are pretty much debris by now. I suppose they might be good for LED blinkies or some other low-voltage and low-current application, but …
So I’ll start using all four of the better batteries and see how the run times work out in actual use.