Most batteries for cameras are Lithium Ion batteries.
The camera manufacturers batteries are in the $100 (in Canada), that’s for Canon, Nikon, Fujifilm… There are also plenty of batteries that are supposed to be compatible with the same model number that cost only 10% to 20% of the camera manufacturers batteries.
Most Lithium ion batteries for cameras are between 7.2 volt to 7.8 volt because they are made of 2 cells with each cell having a charge of between 3.6 to 3.9 volt.
As far as I know, there are only 5 manufacturers of these Lithium Ion cells: 4 in China and 1 in Japan. Even Tesla doesn’t manufacture the Lithium Ion cells for its own car batteries, they use cylindrical Panasonic 18650 Lithium Ion cells.
The camera manufacturers like Canon, Nikon & Fuji “farm” out the manufacturing of their batteries to companies that specializes in the “battery business”. These companies assemble the various parts of the battery and package it according to the various requirements. The battery manufacturers do not make the battery cells, they manufacture the plastic, the casings and add the extra parts like sensors…
The Lithium Ion cells are graded from grade A, the highest quality, to grade C, the lowest quality.
Grade A cells are the better ones and they (are supposed to) conform to the UL1642 standard. The others don’t. When you buy a Canon, Nikon, Fuji… these cells have passed the UL1642 tests. It’s a quality assurance that is supposed to prevent the batteries from exploding and/or catching fire, or from draining when there is no usage, or chemical leaks….
The UL1642 standard for Lithium Ion batteries is no guarantee. Ask Boeing about their Lithium Ion batteries catching fire with their 787 Dreamliners in 2013-2014.
The “copycat” batteries could be of grade A quality but without the actual UL1642 testing, it doesn’t matter since nobody will ever know. If there’s a problem, the reseller doesn’t really care, the reseller will exchange the battery.
The problem is that we have no idea what kind of cell are being used inside the “copycat/3rd party batteries” batteries.
I have been using NP-W126 from UpStart because they are sold by a local dealer. I’ve been very happy with them.
And no, their charge does not last as long as the Fuji OEM batteries. I would say about 70% but I think that paid $20 Canadian for 2 batteries.