I use a simple
USB Meter although they're cheaper direct from China. I have a few so I've been able to calibrate them by comparing results from discharging and charging the same battery. I've only had one faulty meter so far.
If I use the official Samsung Charger Case then the capacity measures very close to the 3220mAh claimed, usually +-20mAh. If I charge the battery in the phone then the capacity is about 6% less than that shown by charging in the Charge Case.
I've bought around 30 Samsung branded batteries from Amazon, eBay and Samsung UK as well as a couple of other places I won't mention as they should know better and may have been one-offs. 11 of them were genuine, the fakes were either returned for a refund or refunded without hassle once I started quoting the measured capacities.
The fakes generally measure between 1900mAh to 2300mAh and I so far I've been able to identify the them in advance by reading the QR code. If the code doesn't consist of the Product reference+batch number+serial number e.g. GH43-04309A+AA1H119yS+00184 then it inevitably follows (always so far) that they won't have anything close to full capacity. Some of the fakes are starting to come close to the originals in terms of printed font, font colour and even having most of the QR code but none so far have included the final 5 digits which are actually the serial number of the batch. The batch number is unusually printed on the battery as the S/N and it can be the case that 2 genuine batteries have the same S/N printed on them but also have the additional unique 5 digit serial number within the QR code. I got lucky one day and actually spoke to a Samsung techhie who didn't follow the company line that any batteries not bought direct from Samsung were automatically fakes and gave me more information on how to identify them.
I have 3 x N910Fs which is one of the reasons why a have a large stock of batteries (I also have Anker and RAVPower).
