Comparing a couple of copy lithium-ion battery chargers. I ignored the "do not open" bit, as this kind of thing is what might be referred to as, my specialist subject, and necessary precautions were taken.

Will be similarly investigating a genuine Nikon version shortly, and may do some operational comparison tests to see if they operate as such a charger should. One key thing about these type of chargers, is that for lithium-ion type batteries, once they're charged, the charger completely stops charging. There should be no trickle charging that other battery types tolerate.