I made the following report 6 months ago and am just now posting the information. Also have an Excel spreadsheet and additional images beyond the one graph below.
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There has been considerable discussion on the Sony Alpha A6000 camera batteries since the camera was released in early 2014 because the relatively small battery does not have a large capacity. Much of the Internet and forum information has not had much value as users make vague assessments of what they seem to notice. I've been an electronic tech in Silicon Valley for decades. The capacity of my Sony battery was 1020 miliamp-hours at a nominal 7.4 volts. Other brands have often been rated higher while informal user assessments have tended to indicate the Sony battery has more capacity than off brands. I found that true for off brands in 2014 but since 2015 have been buying DSTE batteries that actually last a bit longer than the Sony battery. Although they are rated at about 180% of the Sony capacity, they don't have that much more relative capacity.
Some may wonder why I own so many spares? It is because I sometimes backpack away from power charging sources for as long as 10 days at a time. I also multi row column stitch blend and focus stack frames, both of which add considerably to my shot counts. Otherwise I use known methods and camera settings to reduce current drain like shutting off the camera between shots.
It is difficult to measure the battery voltages or current because the camera contacts are small and with the battery inserted, not visible. I modified two of four Wasabi battery chargers I own in order to connect DMM meters to the contacts. The two sections of the chargers can be easily separated. A small bare wire can then be easily placed in the spring metal charger contacts that is clamped tightly when reassembled in order to externally monitor voltages on the other end of the wire.
I only own the A6000 and not other Alpha models. It is difficult to assess power drain on these cameras because much depends on its complex settings and operations. A more straightforward battery test per below instead loads its NP-FW50 batteries with a 20 ohm resistive load thus eliminating camera variables. At a nominal 7.4 volts, that results in a 370 milliampere load. Although the load is somewhat greater than camera operations, the resulting relative voltages over time reflect valid storage capacity and drain characteristics.
In order to test each of the 19 each NP-FW50 batteries I now own, I first fully discharged batteries with a static 10 ohm load. When the Sony Lithium Ion battery discharged from the fully charged 8.3 volts to 4.94 volts, the internal battery disconnected with resulting voltage zero. In other words internally with the battery packs, a circuit prevents battery voltages from dropping below a threshold value in order to prevent battery damage caused by further discharge. I used a timer to assist alerting me in order to monitor voltages every 15 minutes. When after a 15 minute period a battery had dropped to zero, I would end its test, fully charge it, and then verify after charge it showed a similar voltage to its unloaded value before the test.
When battery voltage is lower than 1%, the A6000 displays a slash across its battery indicator. When it goes somewhat lower it will power off and upon powering on displays BATTERY EXHAUSTED. I found with the Sony battery, when the unloaded battery voltage was 7.39 volts or the 20 ohm loaded voltage was below 7.01 volts, it displayed a slash across the battery indicator. When the unloaded voltage reached 7.23 volts or 6.96 with a 20 ohm load, it displayed BATTERY EXHAUSTED. Thus the camera shuts down well before the battery itself disconnects its output and that is indicated on the charts at that 6.9 volt line. All values above 6.9 volts are shaded yellow indicating the operating range and that shows the batteries with highest capacities are active twice as long as the weakest.
On the chart, the Sony is battery number 1 that came with the camera. Bought in 2014, batteries 2 through 4 are Wasabi and battery 6 and 7 (bad), are Sterlingtek. Bought in 2015, batteries 8 through 15 are from DSTE as are batteries 16 through 19 just bought now in June 2018. I just ordered an additional 4 DSTE batteries thus have bought 8 new batteries as a result of the test in order to not expend extra effort adding inefficient weight to my already heavy backpack. Each battery weighs about 1.6 ounces thus 10 weigh one pound.
I found batteries out of the camera hold their full unloaded charge value for at least a week without noticeable change. My least favorite feature of the A6000 is its power switch because it can easily be bumped into the ON position say while in a daypack that may discharge its battery. Accordingly I tend to remove a battery during periods the A6000 is being transported, not in use, or overnight. Adding a 20 ohm load immediately drops the battery output voltage by about 0.3 to 0.4 volts due to internal resistance within batteries and that is shown at the 0.1 minute point on the graphs. If one removes such a load, battery voltage bounces back up to near what it had read unloaded.
Besides the Sony battery, I bought 3 other brands. Only one of the batteries, number 7, was unable to power the camera for more than a few minutes thus bad. Battery 2 and 5 were functional though with poor capacity. Two batteries, number 5 and 6 initially seemed bad in that they held little capacity after seemingly being charged until I had performed a couple full discharge and charge cycles, after which they have been performing ok though with weak capacity. Thus it may be possible to recover a faulty battery by fully discharging it and then recharging. The spare batteries I bought in 2014, numbers 2 through 6 had lower capacity. Batteries bought in 2015, numbers 8 through 15 from DSTE have more capacity than the Sony. I bought 4 more from DSTE after starting the test, numbers 16 through 19 that show modestly greater capacity than identical types with a couple year's use. Thus at least with that brand, it does not show significant aging.
The best batteries lasted 2.5 hours with the 370 milliamp hour load that is roughly between 900 and 1000 milliamp hours of usable capacity. Generally batteries discharge at a consistent rate until a knee is reached around 7.1 volts, after which the rate of output voltage drop increases. Just below that knee is also where Sony shuts down the camera with the BATTERY EXHAUSTED.
