Dummy battery voltage confusion

[Orson Maxwell]

Ok so apparently everyone (Amazon and local dealers in Moscow) sell this DC kit for my Fujifilm X-T2 that contains a dummy battery and a 9V adapter. They are very adamant about using the dummy battery with their adapter.

Naturally, my interest has been aroused by that. At first I thought maybe there was some protective electronics inside the dummy like a voltage stabilizer or overvoltage/mispolarity protection. So I got one and probed it with the multimeter - the battery plus and minus terminals were wired directly to the DC jack so that theory goes out the window.

Now it looks like it's just pure marketing, but I'm still unsure about the voltage rating. If they were producing the battery to be used with a wide variety of common 9V supplies, I would understand the voltage rating. But since they has gone to some lengths as to forbid using any DC brick other than their own (and even made the DC jack a 5mm one instead of the common 5.5mm), I'm curious - what gives? Does the camera react to a higher than nominal voltage on the battery port in some way? the original battery is of course Li-Ion 2S 7.4V.

I had no issues powering the camera via a dummy with a li-ion battery pack of 4x18650 just like I was doing with my older Sony, but it looks dodgy still - I feel like I'm missing something.

I'll be obliged for any input.

[Orson Maxwell]

Well as I expected, directly connecting a pack of Nx2S li-ion batteries did the trick - as expected, the camera considered them to be just an ordinary battery and because the chemistry is the same, it also correctly shows the state of charge on screen. Thanks, fujifilm engineers, for not going the smartsy-fartsy chipped battery route.

Also I'vee a thread about camera overheating on dummy battery - that might be related to some amount of overvoltage that I described in the opening post.