Dynamo drag, day time light, standlight broken

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peterh11
Posts: 290
Joined: 20 Mar 2010, 10:25pm

Dynamo drag, day time light, standlight broken

Post by peterh11 »

Hi,

On one of my bikes, I have a SON28 hub dynamo, a B&M IQ-X headlight and a B&M toplight line rear light. I've had this setup about 3 years. Here are a few questions for those of you who take an interest in electronics and dynamo lights.

I had always assumed that the daytime light function on the IQ-X would use less power than the full beam, and so I just left it on all the time. However, recently I rode a familiar route in bright sunlight and turned the light right off. Testing turning on and off a few times in succession, it felt there was a small difference in the ease of pedalling, though not enough that I could tell whether the light was on or off without looking. My average speed on that ride was however a bit higher than expected for the effort (0.5-1kph?) Also, on a ride with a friend who is a bit stronger than me, it felt easier to keep up with the light off. Anecdote and hardly a proper scientific test I know!

So I tried a simple test: turn the bike upside down and spin the front wheel and time how long till it stops a few times, trying to apply the same force with and without a cover over the light to force to night or day mode. This is a crude test of course. But it seemed that the time to stop was about the same independent of daylight or night mode. Perhaps not so surprising as the daylight mode small LEDs are very bright.

Question: has anyone done a proper controlled measurement on this or got data from B&M?

For now I am turning the light off on bright days. I have no problem pedalling harder when I need the light, but don't want to otherwise!

I looked on the internet - as you do - and I found this: https://www.cyclingabout.com/dynamo-hub ... n-shimano/ which has some measurements for the same dynamo and headlight (no tail light I think). This says at 20kph, the power output is about 4.5W and the drag is about 10W, which is quite a lot for a normal person like me who generates probably 100W or so on a long ride. Also it is more than the common figures reported from testing with a resistor load.

Question: can anyone explain in relatively simple terms why the difference in efficiency between resistive load (I guess similar to a traditional bulb) and an LED light? I had naively assumed that a modern dynamo like the SON28 would have been designed to maximise efficiency with an LED light. But I am no electronics expert.

Finally, last Sunday it was a very dull day so I put the lights on (that's what they are for after all). It was dim enough that the full beam came on some of the time. But now I see that the standlight has failed. The LEDs are ok - the same ones are used for daytime light and standlight and they run fine as long as the bike is moving. So I guess whatever stores charge (a capacitor I suppose) has come adrift or failed. The rear light's standlight works fine. The light is 3 years old so well out of warranty.

Question: Has anyone had this problem and successfully fixed it?

For now I will put a Cyo Premium from another bike on, and put an older spare on that bike. I'm a bit disenchanted with the IQ-X as while it is very bright, the beam shape is narrower than the Cyo Premium and the switch is a push-button one you have to press while the capacitor (or whatever it is) has charge (in practice, while moving at the moment). Then I will take a close look at the IQ-X and see if I can dismantle it to check inside.

PeterH
Jdsk
Posts: 24639
Joined: 5 Mar 2019, 5:42pm

Re: Dynamo drag, day time light, standlight broken

Post by Jdsk »

peterh11 wrote: 27 Jan 2022, 8:51pmI looked on the internet - as you do - and I found this: https://www.cyclingabout.com/dynamo-hub ... n-shimano/ which has some measurements for the same dynamo and headlight (no tail light I think). This says at 20kph, the power output is about 4.5W and the drag is about 10W, which is quite a lot for a normal person like me who generates probably 100W or so on a long ride. Also it is more than the common figures reported from testing with a resistor load.
On the drag characteristics and output of the generators see also Chris Juden's review in 2012:
https://www.cyclinguk.org/sites/default ... ynamos.pdf

(That's the study that got me interested in modern hub dynamos.)

Jonathan
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andrew_s
Posts: 5795
Joined: 7 Jan 2007, 9:29pm
Location: Gloucestershire

Re: Dynamo drag, day time light, standlight broken

Post by andrew_s »

I've also heard tell that the daylight running lights have quite a high power consumption, not much short of the nighttime lights, and have therefore avoided buying lights with them (from the pount of view of charging things when touring, rather than drag as such)
Jdsk
Posts: 24639
Joined: 5 Mar 2019, 5:42pm

Re: Dynamo drag, day time light, standlight broken

Post by Jdsk »

And there's a lot of information on B+M lamps (and others) at Peter White Cycles:
https://www.peterwhitecycles.com/b&m-hl.php

Jonathan
peterh11
Posts: 290
Joined: 20 Mar 2010, 10:25pm

Re: Dynamo drag, day time light, standlight broken

Post by peterh11 »

Jdsk wrote: 27 Jan 2022, 9:01pm
peterh11 wrote: 27 Jan 2022, 8:51pmI looked on the internet - as you do - and I found this: https://www.cyclingabout.com/dynamo-hub ... n-shimano/ which has some measurements for the same dynamo and headlight (no tail light I think). This says at 20kph, the power output is about 4.5W and the drag is about 10W, which is quite a lot for a normal person like me who generates probably 100W or so on a long ride. Also it is more than the common figures reported from testing with a resistor load.
On the drag characteristics and output of the generators see also Chris Juden's review in 2012:
https://www.cyclinguk.org/sites/default ... ynamos.pdf

(That's the study that got me interested in modern hub dynamos.)

Jonathan
Thanks. I’ve seen this article (or perhaps another version). To be clear, I am a big fan of dynamo hub lighting with LED lights, and every bike I own has it.

He notes in the “how they were tested” section of his article that the graphs he shows are based on Olaf Schulz’s tests with 12ohm resistors, and these tests are the ones I was referring to in my post. He expects modern generators (hub dynamos) and LED lights to perform better.

However, this other newer report seems to suggest that while you can get more power, it is at the cost of proportionally more drag. This is what surprised me. The newer set of tests doesn’t include a SON28 or SON Delux tested with Schmidt’s own current lights - maybe the results are different for these.

PeterH
peterh11
Posts: 290
Joined: 20 Mar 2010, 10:25pm

Re: Dynamo drag, day time light, standlight broken

Post by peterh11 »

andrew_s wrote: 27 Jan 2022, 9:23pm I've also heard tell that the daylight running lights have quite a high power consumption, not much short of the nighttime lights, and have therefore avoided buying lights with them (from the pount of view of charging things when touring, rather than drag as such)
Yes, I’m there now. If I can’t fix this one, I won’t be buying another IQ-X. I’m a bit disappointed that B&M seems to be moving to daylight running on their newer high end models. They do still have the Cyo Premium on their web site but for how much longer? I might just grab one to put in my spares box.

PeterH
HakanC
Posts: 7
Joined: 2 Jan 2021, 3:51pm

Re: Dynamo drag, day time light, standlight broken

Post by HakanC »

peterh11 wrote: 27 Jan 2022, 8:51pm The light is 3 years old so well out of warranty
Pity aabout Your light
But were did You buy it? Some retailers (all?) offer a five year warranty for B+M IQ-X

Look at this from Rosebikes
Image
https://www.rosebikes.com/b-m-iq-x-led- ... ape=silver
and
https://www.rosebikes.com/termsandconditions
From Sweden
peterh11
Posts: 290
Joined: 20 Mar 2010, 10:25pm

Re: Dynamo drag, day time light, standlight broken

Post by peterh11 »

HakanC wrote: 28 Jan 2022, 5:01pm
peterh11 wrote: 27 Jan 2022, 8:51pm The light is 3 years old so well out of warranty
Pity aabout Your light
But were did You buy it? Some retailers (all?) offer a five year warranty for B+M IQ-X

Look at this from Rosebikes

https://www.rosebikes.com/b-m-iq-x-led- ... ape=silver
and
https://www.rosebikes.com/termsandconditions
Interesting, thanks for posting this. I bought it from Bike Discount DE. I just took a quick look on their web site, nothing obvious but will dig deeper when I have a chance, and send them a query. I notice it says “manufacturer’s guarantee” so seems hopeful. Would be good if I can swap it for a fully working one. I also notice that the price is way below what most UK retailers are charging, though they won’t ship to UK except on an order over £175 now.

PeterH
Jdsk
Posts: 24639
Joined: 5 Mar 2019, 5:42pm

Re: Dynamo drag, day time light, standlight broken

Post by Jdsk »

peterh11 wrote: 2 Feb 2022, 7:47amI also notice that the price is way below what most UK retailers are charging, though they won’t ship to UK except on an order over £175 now.
Very useful running thread on buying from the EU including what's changed and some experiences:
viewtopic.php?t=142589

Jonathan
peterh11
Posts: 290
Joined: 20 Mar 2010, 10:25pm

Re: Dynamo drag, day time light, standlight broken

Post by peterh11 »

peterh11 wrote: 2 Feb 2022, 7:47am
HakanC wrote: 28 Jan 2022, 5:01pm
peterh11 wrote: 27 Jan 2022, 8:51pm The light is 3 years old so well out of warranty
Pity aabout Your light
But were did You buy it? Some retailers (all?) offer a five year warranty for B+M IQ-X

Look at this from Rosebikes

https://www.rosebikes.com/b-m-iq-x-led- ... ape=silver
and
https://www.rosebikes.com/termsandconditions
Interesting, thanks for posting this. I bought it from Bike Discount DE. I just took a quick look on their web site, nothing obvious but will dig deeper when I have a chance, and send them a query. I notice it says “manufacturer’s guarantee” so seems hopeful. Would be good if I can swap it for a fully working one. I also notice that the price is way below what most UK retailers are charging, though they won’t ship to UK except on an order over £175 now.

PeterH
Checked Bike Discount’s web site and their T’s and C’s page says 2 years warranty with a few listed exceptions. Ah well.
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