I've finally got around to testing some dynamos. I got Paul to make up a bracket to hold them on the tyre testing rig, so I've just measured the power taken to drive the wheel on a roller with the dynamo on the tyre and with it off. Wheel loading was reduced to about 23kg instead of the usual 30kg for rolling resistance testing. This time, I'm just quoting the raw amps difference between the dynamo off the wheel on the wheel.
Results are the av. of five runs, discarding the highest and lowest.
I used the Lumotec headlights with 3 watt QI bulbs. This does not measure the amount of light produced, but will give some idea for the relative amount of power required to drive the dynamos. I've used the S6 on a trike, and was not able to detect any increase in resistance from the dynamo in riding the trike.