Let's look at another use case, the daily commuter. Battery won't quite stretch to two days' commute, so it's charged nightly. Four months a year, 20 days a month, 80 charges per year. That 1000 cycles is developed for a charge of 50% oritinal capacity at room temperature; on cold days it's de-rated 50%. (Yes, unfortunately, manufacturers play games like this!) That battery is good for no more than three years. Freeze it in the garage, cook it a time or two, and you'll be lucky to get two years out of that same battery.

Even though I wasn't commuting as much back when I used battery lights, I never got more than three years out of a battery.

I have them on my bike, and I agree they are amazing. I still wouldn't go passive only, but they sure are good.

See how they light up in my camera flash

http://bikeforums.net/attachment.php...hmentid=338763

I mentioned them in an earlier post myself:

Back to the cost of dynamo systems - I priced up my hub dynamo setup earlier:

That is for a hub dynamo setup. I am putting a bottle on my wife's bike and despite my efforts to decide the best budget lights, she has decided what she wants ;).

so this is what I am putting together for her:

Axa HR Traction Power Control Dynamo (Left) - £13.96 GBP
Axa Pico 30 T Steady Auto LED Front Light - £17.43 GBP
Axa Riff Steady LED Rear Light - £7.80 GBP
P&P - £5.17
Bottle dynamo bracket for cantilever/V-brake mounting - £4.50 GBP + £1.99 GBP

That comes to £50.85 GBP (€60.43 EUR, $79.27 USD) - that's 2/5 the price of my hub setup for a perfectly adequate system.

That's one of the reasons I only used 1/10 and 1/4 rated cycles in most of my examples, that last line was a bit of a stab. I doubt anyone would get the full rated life of any cell.

The latest eneloop's are supposedly rated to 1800 charges, assuming that we can only rely on 1/4 of this - that is a maximum of 450 charges.

In theory, based on your scenario of 80 charges/year - they should last over 5 years.

That said, I don't doubt your real world experience - I am only going on theory.

All that aside, the OP is looking to avoid recharging batteries anyway.

Just to add to this part of the discussion; I have Li-ion batteries that I've had for at least three years that are still very useable. A short while back I was testing one of my new lamps and was using my old batteries. I was amazed at how well the old batteries still worked.

I'm sure if you were to ride in the dark an hour everyday using the same battery, eventually the battery will lose much of it's original capacity. All the facts and numbers suggest this to be true but if you are only using them for occasional recreational use they should last a good number of years ( provided the cells are of decent quality ).

Another factor to consider with battery power lamps is how they function in cold weather. Li-ion batteries actually work well in cold weather. If there is a problem with diminished run time it is usually because the lamp head has built in low voltage protection. This protection works fine in moderate temperatures but when Li-ion cells get cold the internal resistance of the cell increases. This causes more of a voltage drop internally with-in the cell. The lamp circuitry can thus misinterpret this voltage drop to mean that the battery is losing voltage. If there was a way to readjust the circuitry for winter use this wouldn't be a problem but since there is no way to bypass the circuit, lamps that have the voltage sensing circuitry will at some point power down when they shouldn't. Some of my lamps have the circuitry and some don't. If you use a battery that has more capacity than you need then it usually isn't an issue either way.

If I was a die hard commuter and was using lights everyday I would certainly consider a dynamo if just for convenience sake. On the other hand if I commuted only occasionally by bike the battery power lights are fine. Like I said before if you need a dynamo for non-supported touring or endurance events a good dynamo set-up would certainly make a lot of sense.

That's the point. I don't have to buy one for each bike. I buy one light system that I can fit to all of my bikes. If I want to ride my commuter bike, I plug in the batteries and take off. If it snows and I need to ride my winter mountain bike, I move the lights over to that bike and off I go. If I happen to want to cruise after dark on the cruiser, I swap the lights and go cruise. If I want to go mountain biking, same thing. If my wife want to come with me, I have enough lights that I can put them on her bike and on my bike and we can go for a night ride. That's maximum flexibility at a reasonable cost.

Compare that to doing the same with dynamos. I have 26" wheels without disc, 26" wheels with disc, 700C wheels for a race bike, 700C wheels for touring and commuting. And my wife has a 26" wheel mountain bike and a 24" wheel Terry. So to go the dynamo route, I would need, at a minimum, a 26" disc, a 26" wheel rim, a 700C rim, a 24" wheel rim and another 26" wheel rim. I'd need harnesses for my 7 bikes and her 2. Maybe I could move the headlamps around but that's hardly "convenient" enough to just hop on the bike and ride, is it? And cost wise that's going to run to around $1000 worth of equipment.

I could equip just one bike with a dynamo system and use it all the time but that's not why I own 7 bikes. I enjoy switching them up and using a different bike so that the commute (most of my riding is commuting) isn't quite as boring.

Reflectors do their job but they are no substitute for active lights. And to say that they are 'brighter than any bike light' is just a silly statement for all kinds of reasons.

I specifically said they were used IN ADDITION to active lights. Indeed you were the one who earlier claimed that reflectors were nearly useless indeed what was it that you actually said? Oh yes it was


But I guess you have finally realized how silly that statement was...


Yes, my statement was silly... Of course I provided examples of how it was accurate, including DAYLIGHT riding... But feel free to stick with your personal beliefs.

Yes, if the batteries are only lightly used they can last longer than I stated. My statement was based upon using those batteries 5-6 days a week for up to 3 hours at a time... I actually now use my dyno lights more than that, simply because I don't have to worry about running out of battery power.

Actually no, they don't work well in cold weather. Li-ion (and many (all?) other rechargeables) have their charge level determined by the voltage they are capable of delivering. The low voltage available when cold is THE indicator of holding less charge. The circuitry isn't misinterpreting anything, and it certainly isn't possible to 'adjust' the circuitry to deal with the lower voltage and get the same total power from the cell that it can deliver when warm. That internal resistance, actually discharges the battery. That is why a battery that isn't even used will 'loose' its charge over time.

A 'discharged' condition is determined solely by the voltage across the terminals. For Li-ion it is completely discharged at approximately 3V
A 'charged' condition is determined solely by the voltage across the terminals. For Li-ion it is fully charged at approximately 4V

http://bikeforums.net/attachment.php...hmentid=338885

I'm going to ignore the rest of your post and concentrate on the accuracy of your statement

Let's assume that a car light has an area of about the same as a 2"x4" reflector. It doesn't and a 2"x4" reflector is larger than anything I've ever seen incorporated into a light but, for sake of discussion, let's assume they are equal. A car lamp puts out 1500 lm and a 2"x4" are is 0.005 sq meters. The lux, a measure of lumens per unit area, of the car lamp is 300,000 lux at the lamp face. Using the inverse square rule, the intensity of the light at 25 feet is 480 lux or 480 lm/sq m. The amount of light hitting the reflector is 2.4lm. If the reflector is hit dead on and we assume that 100% of the light that hits the reflector is sent back...not a valid assumption but I'll give it to you anyway...the amount of light that gets back to the observer is 0.0038 lm. Even if the reflector was a square meter in area, the total lux getting back to the observer is only 0.76.

Now to the bike light. A bike light has an aperture of about 1" or about 0.0005 sq m. Let's look at two different light outputs, 300 lumen and 600 lumen. At 300 lumens, the lux at the light is 600,000 lux. At 600 lm, the lux at the light is 1.2 million lux. Again applying the inverse square law, an observer at 25 feet would see 1920 lux. Last time I checked, 0.79 lux is less intense than 1920 lux.

The values above for the light returned would be even lower if you hit the reflector at any angle other then dead on.

So you see, your statement that "NO BICYCLE LIGHT overwhelms the light from a reflector is not accurate. Not accurate at all.

Okay, lets examine your 'facts'

Sorry, but the source itself isn't the size of the light, the reflector is... And as a Tim Allen type yourself you should realize the reflector on a pair of car lights is quite a bit larger

Care to do those 'calculations' for daytime? Or for the lux of a bicycle's light after applying that inverse square law? No, I guess not...

You clearly didn't read my entire statement; "And NO BICYCLE LIGHT overwhelms the light from reflectors, especially in the day time" Nor are you considering that the front and rear reflectors on a bike are also supplemented by the bicycles lights (dyno in my case)... not instead of such lights in my statement... I know you didn't bother to let what I actually wrote conflict with your beliefs;


And of course your numbers are based upon halogen bulbs from 1983 specs, not modern HID or LED bulbs (which are also being implemented in cars as well as bikes, and with far more power available). And you have not addressed car's high beams (which are the most likely to be encountered by cyclists who aren't being seen, ie in a dark environment at night)... Those highbeam produce between 3 and 4 times as much light output...

In short your 'analysis' is what is typically called 'cooking the books'...

It is difficult to have a discussion with you because you don't seem to understand how light works. The reflector just gathers the light from the source and directs it outward. At the lens of a car light, you will have all the light that can be gathered by the reflector. You can't get any more. If you were to place a target at the lens of a car light (or any focused light for that matter), you can measure the size of the light beam and you can be reasonably certain of what the lux measurement of the beam exiting the light is. Many car lights have an aperture of about 2"x4". If they were 3"x5" or 6"x6", it wouldn't matter that much because the area in square meters is going to be about the same magnitude. For the sake of the discussion, assuming a 2"x4" aperture is reasonable.

Why would I need to do the calculations for daytime. They would be the same. The car light would still put out the same amount of light. The reflector would reflect back the same amount of light and the bike would put out the same amount of light. The only difference is that the whole calculation would be moot since the sun light would swamp out any contributions from any light source.

Sunlight falling on the reflector is only going to be reflected to an observer if the observer/sunlight/reflector is in the proper orientation. That proper orientation will only occur in the morning and evening and will be dependent on the direction of travel of the reflector. It will also be dependent on the location of the reflector on earth and the seasons. Early in the morning around this time of year, that lines up if front reflector is traveling east at around 0700. After about 0900, the sun is too high to reflect off the front reflector towards an observer sitting in an automobile. If they were laying on the ground, they might get some reflection depending on how far away from the front wheel they are but you would probably run over them before they would see the reflection and it would be swamped out by the ambient light anyway.

If you set a reflector side-by-side with a 600 lumen bicycle light, then shined a car light at it from 25 feet directly in front of the reflector, you would not see any light coming off the reflector back at the car. The amount of light from the bicycle light is going to completely overwhelm the small amount of light reflected back by a tiny little reflector. And, I'll say it again...the ambient light during the day will swamp out any light coming from the reflector at just about any angle you care to measure it at.


No, the values that I provided are for current technology LED lights. The output of a Cree XML T6 is around 600 lumens for a single emitter. A Cree XML U2 has an output of around 700 lumens. I'm not sure what LED current automotive lighting is using but the most common light you'll run across for automotive lighting is still going to be tungsten or halogen with a lumen output of 700 lumen. High beams are 1200 lumens in a flatter trajectory and I used the high beam value for my calculation. 1200 lumens is not "3 to 4 times as much..."

Nor are cyclists in an urban environment going to encounter a whole lot of high beam lights. There are a few people who commute and night time ride on dark country roads but, by far, most night time cyclists are going to be commuters in an urban environment where high beams are discouraged.

No, I did a run time test the first time I bought a decent LED light and got 3 hours on high. Since then I just charge every few days, I don't keep track of anything. This time of year I'm on high if it's dark, low if it's dawn, strobe if it's daylight, so probably on average 50% utilization so I should expect 6 hours on a charge. I ride about 80 minutes a day and I try to remember to charge after 4 days. Since I don't really keep track very well, I also have a lockblock on my bar and toss a flashlight on if I lose charge in the middle of a ride (I would carry the flashlight/lockblock backup even if I had a dyno - I do not trust any system that much). I rarely have to do that. So at a guess I'm still getting close to the original run time on the batteries.

Since I carry a backup for both front and rear lights anyway, I am very laid back about charging and don't really worry about it at all. If I go out in the morning and a light is dead I swap batteries then - when it's charge time I just swap the battery on the bike with the one on the charger.

Actually from that statement it is you who doesn't understand how light works. You provided calculations of the car headlight lumens and converted them to lux values. Such conversions require an understanding of the lights optics to be performed. I am guessing you made some assumptions about those optics and either are unaware of them or don't want to reveal them.

Because during daylight hours it is sunlight (and its multiple reflections) which cause reflectors to be so useful (and bright)...

Again, you clearly don't understand, nor have you paid much attention to, reflectors. They work quite well, even when the sun is at less than ideal angles. I am guessing you haven't considered all of the reflected light sources that come into play and are simply treating the sun as a simplified point source...


Okay, yes, position does matter, however neither the car nor the bike are static objects. The purpose of reflectors are to catch the 'attention' of folks. To do so they don't need to be reflecting light at the observer constantly...


Okay, I assumed (since your stated values were consistent with) both beams of a car's headlight. And regulations restrict car's headlights to 20,000 candela, while high beams are restricted to 75,000 candela. So my 3 to 4 times is quite accurate...

Simply not true. If as you are claiming we are concerned most about being seen, then low use facilities are the greatest concern and the one's most likely to encounter high beams on, even in urban areas. If traffic levels are quite high, then a cyclist has little to concern oneself with being noticed--at least in any way that technology is going to change. There will be many multiples of external light sources to shine on them and drivers will be more aware since they will be concerned about those other vehicles...





Since I carry a backup for both front and rear lights anyway, I am very laid back about charging and don't really worry about it at all. If I go out in the morning and a light is dead I swap batteries then - when it's charge time I just swap the battery on the bike with the one on the charger.[/QUOTE]

Thanks!

It doesn't make sense to equip all of your bikes with dynamo, for example, I don't have dynamo on my mountain bike, I won't ride that more than 2/3 hours in the dark so there's no need, I use battery lights for that. Same deal with a junker I have, I leave it outside and it has flashlight and blinkie mounts only.

No one says because one has dynamo setups means one have to get rid of their battery setup.

This discussion is becoming quite tedious even for me...and that's saying something. Lux is pretty easy to calculate. It's lumens per unit area. I am assuming a square lamp face and that the light is spreading out in an even manner across the beam profile. That's not a bad assumption considering that a lot of optical engineering has gone into providing drivers with light that is evenly distributed. In other words, car lights don't have a lot of hot spots. The beam isn't going to remain square, of course but, for the purposes of the example that won't make much difference. Lux is actually a much more useful measure of light intensity than lumens...as long as you specify how far from the light source the measurement is made. Lumens measure just the raw output. For the discussion of how the light interacts with the reflector, using lumens isn't all that useful because not all of the light put out by the car's lights is going to hit a 2"x4" target. You can calculate the lux at 25 feet, then calculate the lumens hitting the target, reflect the light back to the source and calculate the lux of that light going back. Saying that 800 or 1200 lumens hits the reflect from 25 feet is just wrong and ignores a whole lot of physics.


The car's lights still put out the same amount of light and the reflector still reflects only a small fraction of that light back. Any reflection you get from the sun is going to be highly dependent on the location of the sun, the location of the reflector and the location of the observer. And the amount of light reflected back is going to change minute to minute as the angle of the sun changes.


The retroreflectors can't violate the laws of optics. They bend them a little but they don't break them. Light hitting the retroreflector will bounce back towards an observer only if the angle is relatively small. Get much the sun much past 25 degrees above the horizon and the light doesn't reflect back towards a driver sitting in a car but reflects down onto the ground. And the intensity is still small due to the small size of the reflector. I watched cars this morning on the way to work. The taillight reflectors of the cars traveling exactly west, did light up from the sun at 0700. By 0730, they didn't. I turned south and the reflectors didn't reflect light at all from the sun. The window for a reflector to have any effect is very narrow. And if I turned back to the east into the sun, reflectors had no reflection whatsoever, because, well, they can't reflect without light shining on them.

I suggest you go try observing this yourself.

If you think that you'll encounter high beams in urban situations, try driving around with high beams on in a car some time. If you don't get flashed by every other car on the road, you'll get a ticket from a cop for operating with your high beams on. That high beams are discouraged in towns is most certainly a true statement.

A reasonable question that got lost in all the sputtering. No, my prior LEDs didn't provide enough light. The halogens I used for a long time were very bright but heavy due to needing 12 subC NiMH cells per light. At around 2 kg per pack and having to carry 3 packs, that adds up to a lot of weight. I tinkered with LEDs for a while and the very early ones like the Nighthawk were abysmally dim. Flash lights from Dealtime were better but limited in run time. Magicshines were okay but new emitters put out more light and the new lights I use have a much narrower beam that I prefer over the Magicshines. I'm used to 12 degree beams from the halogens and the Magicshines are closer to 35 degree beam. Too floody for my taste.

The technology is changing rapidly and the cost is coming down dramatically, why not experiment? At $20 to $40 per lamp, I'm not out much if the 'upgrade' isn't one.

Then what was the point of your post? "Then buy one for each bike" implies that I should get a dynamo for each bike for maximum convenience. I'd rather not. I'm well covered at around $75 thanks.

Aren't these stupid units fun...
Candela and lux are both units that include beam pattern factors. These are a measure of your optics as the light bulb behind them.

Thinking about lighting is fairly simple. Lumens = total number of photons. Candela/Lux = where are the photons are going.

The H7 bulbs on my Subaru are listed at 1450 lumens. http://www.danielsternlighting.com/t...ulb_types.html
The car has two of them for a total 2800 lumens.

1400 lumens is a good LED light, so there's really only a 3-4x difference if you consider that cars have 2 headlights, and most people don't run 1000+ lumen mtb night lights.

As for reflectors, in bright daylight, I can easily see a 50 lumen blinky light from a quarter-mile away or more. Good luck with a reflector.

+1

I've been following your arguments and agreeing, PlanoFuji, but I disagree about reflectors in daylight. I've never observed them reflecting in the day.

I've moved to hub dynamos, just got a new wheel for my Brompton , with a Shimano hub , & B&M head and taillights.

3rd bike.. built a new wheel for my WTR, the Bi Fri was someone else's BTO came with disc brake dyno-hub..


though my 2, battery powered niterider 6v halogen headlights are still working, the 2 bulb 12v one ran out of NiCad recharge cycles,
on both the water-bottle batteries.. havent made the labor /cost jump to a different 12v. as the newer Dynamo serves so well

& 25 years on, My needs got more modest.

Reflectors in my observation are a very weak during the day, a lot of light has to be shined at the reflectors at a perfect angle for any use, but at night within 50 meters they do really shine, especially road signs with their huge surface area, a modest 100 lumen light in flashing mode will light up those easily.

Need pictures of those Brompton and BFs.

I'm thinking about getting a BF and/or Dahon (will be fitted with dynamos of course, but the Dahon will likely do the sidewall dynamo instead of hub).

You don't need them from Me.

The 3rd party site to post them on .. and the camera /phone, I've not done.


They, the Mfg., have websites for their bikes .. and theres a Flicker site full of bikes ..


My 1st used Brompton came with a bottle dynamo, OK in the Dry ,
but just went Zzzz as the drive drum slid over the tire traction band in the wet.

https://farm8.staticflickr.com/7434/...1f76eacc_b.jpg

This is my night/rain road riding bike. Still running battery taillights because I haven't found an adequate dynamo taillight so I'm going to DIY one when the parts come in. Love having a lot of light out in front, when I first started out a 400-500 lumen light would wash out in the rain on the ground but with 1000 lumens, I can see.

OP, May I suggest that you visit the Peter White website www.peterwhitecycles.com to get the info that you may require. It seemed to me to be pretty unbiased, as he sells battery and dynamo operated lights. He has done quite a bit of evaluation on this subject.

LBS don't carry dynamos most of the time because they are expensive, and lets face it, if it's going to just sit there, the LBS needs to move it and a cheaper battery powered light will move faster always. Whether it is better or not is up for you to decide not a bunch of obviously biased bike riders. Ford or Chevy? They'll both get to to where you gotta go, who makes the better truck?

So, now I will weigh in to my preference. On my new bike, I wanted a dynamo, so I went with a SON28 on a new 36 hole rim. A luxos U headlamp, and a toplight brake plus tail light. However, I wanted charging capabilities and this has it, and that's another subject. On my tandem, and mountain bike, I use a flashlight mounted to the handlebars for the rare instance I/we get caught in the dark. I have enuf to think about on a daily basis, without having to remember to take my light or battery pack off to charge it tonight, so I went with a dynamo-its always ready for the task. Both have advantages and disadvantages. It's up to you to decide what will work best in your application.

You have asked for opinions here. Remember, opinions are like butt holes. We all got 'em, and they all stink!:lol:

Also FWIW, I have no attachment to PWC, its a resource for me too. Also, I drive a Toyota Sequoia, and a Kubota Tractor!
Cheers