I checked out how the inside of the i3S looks like; it’s just a plain tube with a spring in it… So there is no capacitor or something that could bump voltage…
If the multimeter is broken it could still draw power. Also you will have resistance in the battery tube it’s self that could be messing up the reading. It’s not a true rms meter.
Yeah, but without the battery, because apparently the tube and spring add 1.3 Volts to it, so you should measure the voltage over tube and spring.
So if you can, stick the (+) probe inside the tube touching the spring.
It should read 1.3 Volts somehow.
Speaking of LSD, maybe there’s some acid in the bottom of the tube, maybe from a leaky alkaline?
I don’t know what voltage aluminium and chrome produce, but that could be it.
Does the light work properly?
Looks like you are taking the second, higher, reading with the cell installed and the head off. Looks like the driver is not in the head but in the body and is boosting voltage so the LED can light up. This is the only way a NiMH or AA can work in a flashlight with a single cell. Pretty much everyone who posted before me knows this as well so I must clearly be missing something here. In the second pic are you measuring at the tail with the tail cap off or at the front of the battery tube with the head off? It’s really hard to see exactly what you are doing.