NP-BX1 Lithium-ion Batteries: Sony vs. Wasabi

With this NP-BX1 battery test fixture in hand:

Sony NP-BX1 battery holder
Sony NP-BX1 battery holder

The discharge tests run at 250 mA, which is probably a bit low, as the HDR-AS30V camera can capture video for about two hours on a single battery. Given the Sony’s nominal 1.24 A·h (love that precision!) capacity and derating the Wasabi’s ambitious 1.6 A·h, two hours suggests a current around 500 mA would be more appropriate, but we’ll go with a lower current for now.

Oddly, the two Wasabi batteries (green & blue traces) outperform the Sony OEM battery (red and purple) in terms of voltage:

Sony NP-BX1 - OEM Wasabi - 2014-01-28
Sony NP-BX1 – OEM Wasabi – 2014-01-28

I can’t explain the small kink just before the big dropoff for both Wasabi batteries. Perhaps the protection circuitry behind the battery terminals has a slight peculiarity?

Looking at the total energy delivered, however:

Sony NP-BX1 - OEM Wasabi - Wh - 2014-01-28
Sony NP-BX1 – OEM Wasabi – Wh – 2014-01-28

The Sony battery says it’ll deliver 4.5 W·h and actually produces 4.8 W·h. The Wasabi batteries claim 5.7 W·h and don’t even come close at 4.25 W·h.

I cross-checked those results by importing the CSV data into a spreadsheet, computing the point-by-point power, finding the average, and then multiplying by the total test time in hours. Doing it a couple different ways says you can eyeball a reasonable value by multiplying the median voltage by the test current to get average wattage, then multiplying by the total test time to get W·h. That’s within a few percent, which is good enough for me.

The camera’s power supply undoubtedly has a low-voltage cutoff, but it’s a single-cell battery and they might just run it down around 2.8 V; in that case, the Sony batteries will last longer. If the voltage cutout is 3.5 V, similar to the Canon camera, then the Wasabi batteries win.

I don’t have enough experience with the camera or the batteries to predict anything based on actual use.