Originally Posted by
ItsJustMe
In any case, if I continued to use a battery powered 2nd taillight, that's 8 watts of draw.
I continue to run battery lights in addition to the dynamo ones, simply from a belt-and-supenders standpoint. For the record, when I ran strictly battery lights, I also ran two on each end, all powered separately. I've had lights die unexpectedly in a commute, and been glad I had the second.
I'm also of the opinion that standlights on dynamo lights dim too much and then are easily lost among the background lights of the city, my primary habitat. The last thing I want is to start from a light, having someone turn left in front of me because the standlight disappeared among the background lights and they forgot I was there.
Originally Posted by
ItsJustMe
A lot of the time in the winter (the only time I really need a light), I'm plowing through poorly plowed, rutted mush. I was doing so last night. When the conditions are like this, I'm only going about 7 to 9 MPH at best, sometimes 4 MPH, steering like mad and skidding the front wheel all over to muddle through the criss-crossing car wheel ruts, for 20 minutes at a time.
Is a dynamo going to be able to deliver the power at 6 MPH to keep a 1000 lumen light and a 3 watt taillight going indefinitely? 20 minutes is too long to expect a standlight capacitor to hold.
Dynamo systems (both hub and lights together) that are in compliance with the German StVZO regulations must achieve full power (from the hub) and brightness (from the lights) by 10 km/h, or 6.2 mph. A homebrew system like you're describing is not going to be in compliance, so there's a very strong YMMV with that.
I have a similar situation on my commute--picking my way through rutted streets and trying to assess, "will the hardpack give way and sideslip or not?" and "will the sides of that rut let me move over to the next one?"
I've found the Luxos-U running in its higher power 90 lux mode is sufficient in those conditions right up until low-speed flicker sets in at around 5 mph. Also a reason I run an auxiliary battery light.
There is no perfect system at this stage of the game--either battery or dynamo. The best you can hope for is to put together a compromise.