I have a professional multimeter:
https://www.velleman.eu/products/view/?id=387040&country=us&lang=en so all should be good.
My leds all light when I put it on diode measurement
Wind readings are non-existent, the turbine is at ground level between obstacles so the speed will be very low on average. It's meant as a 'proof of concept', maybe to build a bigger one later. So actually it's not really a concern
Meanwhile I have connected some more powerleds:
With 8 powerleds in series, the gen produced 25mA @ 23,24V, producing 0,58W @ max. 700rpm (cordless drill)
With 4 powerleds in series, the gen produced 75mA @ 11,7V, producing 0,88W @ max. 700rpm (cordless drill)
With one powerled, the gen produced 110mA. I didn't measure the voltage but with the voltage curve of the led in mind, it must be around 2,5V.
I also drove it as a motor. I don't have 120V here, but at 20V it consumes 23mA.
Maybe the guy at Amazon was able to drive it towards 120V/100mA and then converted it.
I think the above numbers show that the generator is having difficulties generating more than a few watts, which contradicts the findings of the Amazon reviewer that got it to produce 16W. This means that an impedance mismatch is the only culprit left. So how can I match the impedance?
Edit: I tested with another generator of the same size and type, and the same problem occurs: only 20mA at 23V with 8 LED's.
(The LED's are Cree XPE's)