High-output commuter light: Battery vs Dynamo
 

I commute daily with a Light and Motion Seca 400. I ride predominantly at night (early mornings and late nights) and the speed and traffic of my commute dictates that I use a high powered light like the Seca 400, not a smaller LED light (e.g. PB Blaze).

My light and motion battery died a couple months ago , which sucks because those things are $120 to replace. I got just over a year of use out of the battery, which was over the warranty, so they won't replace it. If this is a pattern, I'm not excited about spending $120 a year on a new battery.

I did a little research and found out that the depth of discharge on Li-ion batteries really affects the life of the battery. I had been using the light daily, charging it weekly after the battery ran out, so I guess that explains why my battery died so quickly.

I just bought a $160 6-cell battery (deep discount) designed for the higher output models (greater capacity) with the intent of charging after each use, and using the low power setting to minimize the depth of discharge as much as possible. I'm not sure how long this one will last, but without doing any research on this specifically I'm hoping it will be 3-5 years.

I've also been looking into dynamo's a little bit, and they seem pretty enticing, mostly in the low maitainence, no charging and always available. I'm not too concerned about rolling resistance.

My goal is cost savings over the long term, with a secondary goals of initial cost, effort to install and routine maintainence.

My question is: will the battery last long enough and be little hassle enough to be worth the $160 I just dropped, or for a comparable cost and difficulty with installation, will a dynamo be better for this task?

I know there are a lot of dynamo advocates on here, so if you have a specific set-up or system you recommend, I'd like to hear that as well.

When I used battery-powered lights, I charged them daily (in the winter) so they wouldn't get discharged too deeply. (I guess you learned this one the hard way!)

I liked the dyno system on my commuter so much I bought another for my backup commuter last fall. No more dead batteries, no more waiting 3 weeks for vendor to ship new battery.

Trouble is, a good system is expensive. I'd start around $250 and go up to $500 for a good dyno hub built into a wheel, and something like a a Schmidt or IQ Cyo LED light. At that point, I'll be commuting for a while to pay those systems off, vs. some very decent lights. But I don't have to remember to charge them, I don't have to remember to put them on in the fall, they're available for dark overcasts in the summer. I figure it's worth it to me, although it may not make straight dollars and cents sense. You'll have to figure out whether or not it's worth it to you.

Honestly, I'd just make my own pack. That is an absolutely insane price for a battery pack. I paid $40 for an 8 cell pack for my Magicshine, it's over 2 years old now and still going strong.

Just buy a generic pack and solder on the connector from the old dead pack. 10 minutes work, tons of money saved.

Wow, that seems like an awesome stop gap while I figure out the best way to go. $160 is an insane amount of cash for a battery, but I felt forced into it. Can you post or send me more details about what you did and how you did it?

I figured I'd be looking at $250 minimum. what systems did you get?

For commuting, I think a dynamo is the way to go. The light output is impressive, especially with newer models and optimized optics. The initial expense is definitely a bit of a downer, but it sounds like you're already shelling out a lot of cash for a battery-based system. I've been happy with all the hub dynamos I've used ($35 cheapo Sanyo H27 to deluxe $275 Schmidt SON). I'd say the Shimano family probably offer the best compromise for cost/quality, but I can't provide any data on the long term reliability of any of the hubs I've used (ie. none of them have failed yet...).

One thing to consider is optics. If your commuting light is mainly for 'being seen' in traffic, then my personal preference is to avoid a shaped beam like the Edelux. My Edelux produces a nice beam that is, by European standards, courteous to oncoming traffic, other cyclists, pedestrians, etc., but in my opinion, it doesn't put the light out where it's needed most on the mean streets of North America: in the faces of drivers (obviously not appropriate on trails or unlit roads). I was riding in daylight yesterday with my 14 month old son in the carrier and nearly got ploughed over by a woman turning left, despite being lit up by a Supernova on the front. While indicative that no amount of light can save you from a bad/distracted driver, I also see it as evidence that I live in a city where cyclists are a low priority in a driver's consciousness, so you have to do the best you can...

The downcast beam seems to have caused some concern in Europe as well, as the B&M IQ Fly now comes with 'daytime' LEDs mounted to improve daytime visibility, in addition to the main LED and IQ reflector.

Anyway, it's a very personal choice. I was never organized and meticulous enough to ensure that batteries were always charged/fresh and would often find myself riding home on a dark winter's night with weak/dead lights. A dynamo frees you of that hassle, if you consider it one.

I prefer a dynamo simply because I want reliable lighting at the push of a button, and without the hassles of battery management.

Essentially, I think of it from a motorist's point of view: in my car, I expect to be able to turn my lights on when I want them, turn them off when I don't, and otherwise not put any effort, thought, or money into them. I can't imagine any motorist putting up with the things "battery light" cyclists do.

So far I'm happy with my Sanyo dynohub (built up wheel was $70 on eBay) and a Lumotec Lyt at $49 for my short commute. If you need more light then a CYO is more than twice the light at more than twice the price. I have the CYO on my rando bike and love it for all night riding in the country or in the city. I'm done with batteries other than a map light and backup lights.

This is my approach with my DiNotte 400L system as well.

I have a dynamo system on my touring bike/part time commuter and just love being able to go out the door not having to worry about the lights. Also I love the way my Busch & Muller Lumotec ICQ Cyo switches on automatically when the light levels drop. No need to stop and turn on the rear lights. Oh I have a SON 28 dynamo which is their latest one; meant to be more efficient as well.

One thing you might want to look if you go down this path is the Supernova E3 Triple front light given you sound like you prefer a very bright front light.

Having both systems I have now decided to convert the commuter over to a dynamo system in the before next winter and I suspect I will do the same to my Audax bike as well further down the track or when the DiNotte dies off. Just less hassle for the day to day ride; no more remembering to charge the tailight batteries each week; no oh .... moments because I forgot to charge the front light etc. Worth the initial cost in my view.

Also this website is worth a read ... information overload on dynamos and lights :)

Andrew

I actually went and looked at photos of a L&M pack and it seems that they have a connector right on the pack rather than having a cable leading from the pack. This makes it a little more difficult. Does L&M make an extension cable at all? If so you can use the connector from that. Otherwise it might take some significant hacking to get the battery pack connector separated.

I'd probably look to see if there was any way I could crack the case and replace the cells inside. Replacement cells are about $10 so you could rebuild that pack for $40. That's pretty involved though. There is a place near me that will rebuild battery packs, that might be an option.

Assuming you can get hold of a connector somewhere, find out how many volts the pack is, buy one of the same voltage from someplace like batteryspace.com. Assuming it's 7.2 volts (or thereabouts), pick up a 4, 6 or 8 cell pack with about that voltage. Or heck, buy a MagicShine pack. It's not like Light & Motion has special custom electrons that they pack into their batteries, volts are volts. Then hack off the connector if the pack came with one, take the connector off of the L&M pack, solder them together (making sure to get the polarity right) and wrap it up with electrical tape.

I just want to have lights that work and I don't have to worry about. My commuter has a Lumotec Lyt and a cheap Shimano dynohub. I'm working on mounting a dyno taillight too, although that will always be used with another light.

unterhausen brings up a good point: dynamo taillights can be kind of a pain in the butt to mount and, in my experience, aren't fantastically bright. Bright enough? Sure. But not as bright as some of the 0.5-1W+ battery taillights out there. I'm pretty happy with my Supernova taillight and I have a B&M fender mounted light on another bike that I feel does a good enough job, but I'd really prefer a brighter taillight and will often back it up with a PBSF. The wiring, if done well, can look good and be trouble free, but I find it always takes a bit of effort to get it right.

Very well said. I like my Cyo N for unlit highways, but for commuting in city traffic, I routinely supplement it with a battery-powered light that sprays light all over the place, because the cutoff-equipped dyno lights just don't look very bright from above the cutoff. It's too easy to be overlooked amidst the other traffic.

Another problem to take into account: when you stop, the light goes on its standlight and runs even dimmer. That's not good when you're in the middle of a hectic 4-lane arterial intersection, waiting to make a left turn. My Supernova had an exceptionally feeble standlight, the Cyo is better, but this is another area where battery lights can save your bacon.

Another good point. The Supernova standlight is pathetic and I'm not crazy about the Edelux's either. The taillight is significantly better, perhaps because of the way red light is perceived or the efficiency of the LEDs? Having been experimenting with standlight designs, it seems to me the reason standlights are so dim is that the super capacitors that run them are expensive and big. In order for a small/cheap supercap to power a standlight for a reasonable amount of time, the current has to be kept low. My DIY standlight is very bright, but it uses an $8 supercapacitor that wouldn't fit in an Edelux or any of the B&M headlamps.

I run both dyno and battery lighting. Feature comparison:

1. Dyno is dedicated to one bike; battery power lights can be easily moved from one bike to another.
2. Dyno never needs charging; just ride.
3. Dyno has unlimited ride time.
4. Dyno tends to be not as bright as battery lighting.

There isn't a clear advantage one way or the other as far as I'm concerned. Both have their advantages and disadvantages.

Personally, I've had pretty good luck with my CygoLite. Hardware has lasted, quick release everything, battery lasted almost 4 years, replacement was readily available and relatively cheap ($40).

In my DIY dynamo system, I've also had issues with the standlights. One of the problems with capacitors in general is that none are perfect; they all have an Equivalent Series Resistance value. They also have low operating voltages, requiring several to be run in series to build up the required voltage rating. According to my calculations, the ESR on my supercaps (2x Panasonic 20F, 2.7V, for 1 XP-G LED), the voltage drop induced by the supercaps is sufficient to actually dim the LED-this has to do with the Current vs Voltage curve of an LED, which is basically exponential. When running on low current (about 2.8V for 500ma), a difference of -.3V (for 2 capacitors with 300mOhm ESR) puts the LED wayyyy in the low range of its output. I haven't gotten around to splicing in a multimeter to check the current as I ride (project for this weekend), but I'm pretty sure this is why I have disappointing performance on my light when the standlight capacitors are installed.
Low-ESR supercaps are typically (one or both:) more expensive or lower capacity. I've just got my hands on a few 10F caps that have only a 26mOhm ESR, I'll be trying those on my backup system soon.

I know this is the Cold Fusion/Free Energy of dynamo lights, but I'm also working on a dynamo buck regulator. I'll let you guys know how that goes.

At the risk of derailing the thread, I'll just quickly say that I've also been working on a dynamo buck regulator (details in my blog) and it does seem to work quite well with a single white power LED. The more common solution to squeeze more power out of a dynamo seems to be to put several LEDs in series. The Supernova E3 triple does this, presumably with some kind of buck/boost regulation?

In any case, I don't fully understand what you're saying about supercap ESR dimming the LEDs, which would probably be resolved with schematics. This thread's probably not the place, but perhaps more conversation is warranted over pm or over at CPF? :) edit: oh wait, I see you're already active over there.

I have a fairly recent Supernova E3, and I think the standlight is pretty good. You can tell a difference when you stop, but it's not all that much. I have the single LED asymmetric, so it's possible that other versions of the light see more dropoff of the light output.

Mine is 5 years old, which is eons in the world of LED technology. Glad to hear the standlight has improved.

Looking at some tutorials, a rebuild doesn't seem TOO hard. I guess it all depends on how buried that connector and it's circuitry is. but I guess that's why they made dremel tools. The L&M battery is 11.1V, and they sell several types of 11.1V packs online. It's gonna look clunky, and may explode, but I think it'll work. My question for this in particular is if I should go with Li-ion or Li-ion polymer. Probably the former, since that's what the L&M is.

Thanks for the inspiration.

That's the same model I had, from ~2 years ago: asymmetrical E3 Pro. After 30 seconds, it was dimmer than a high-end keychain light running on a button battery. Good luck showing up against this backdrop...

http://i240.photobucket.com/albums/f...gon/cutoff.jpg

I make a left turn from a very narrow left-turn lane here daily.

Where I am happy with the Light from my Edelux headlight.

But I did have a 2 light Nightrider and with 2_20w halogen bulbs
and the 12V battery pack it was quite bright
for most of the battery ampere hours available.

Dynamos on bikes are 6v3w,
[there is 1 bottle dynamo
from Germany that is 12v]..

battery pack sizes are up to what size you want to assemble.
solder together the cells, box them up, etc.

You have nothing to lose but the price of the raw cells if the current pack is dead. As long as you put it back together carefully so the cells don't short it's not going to explode because you still have the protection circuitry from inside the pack.

Unless I missed something, Lithium Polymer is all flat packs like in a cell phone. You want LiIon which is cylindrical cells.

Also suggest you get a helmet light.
 

If you are regularly commuting in the dark, may I suggest also getting a good helmet light? Some of the relatively low-cost flashlights using a single LiIon 18650 or the smaller 14500 complement a bike-mounted headlight very nicely. Advantages are:

1. Redundancy
2. Looking ahead into corners
3. Briefly flashing it at motorists to help get their attention (including, if available, a flashing mode in daytime)
4. Assuming you use a helmet, the light is always with you. No additional gear to put on & take off the bike
5. If you need to do repairs on the ride, it is very handy for task lighting.

p.s. I've used the UniqueFire G10 CREE XP E R5 5-Mode 350-Lumen White LED Flashlight with Strap (1*14500/1*AA) since August. Bright (although clearly not really 350 lumens), lightweight and has a slow strobe mode. Be certain you get one intended for LiIon 14500; they sell what appears to be the identical light but with different electronics for NiMH AA power and users report those fail when using the higher voltage LiIon cell:
http://bikeforums.net/attachment.php...hmentid=248232

Well! I've got a Shimano and a (last generation) SON hub, and I can't tell the difference when it's dark. (The SON generates serious coolness points when people can read the label!)

My Edelux is a lot brighter on a unlit, tree-root infested, tree shaded bike path. The IQ Cyo is bright enough for me everywhere else. I've not seen the Lumotec Lyt, but some people have them and like'em. So my low-end system would use the Shimano hub and IQ Cyo (+/-R).

I supplement these with some decent AA tail blinkies. The Blackburn Flea has a pretty good flash mode, and is helmet mountable, if you want to aggravate a motorist; but even that didn't stop some retiree who was too old to be driving from trying to run over me in my one-way turn lane (had to dodge to the left, into HIS turn lane, and yell at him enough that I hope his wife took over for me). Short of a James Bond-style laser to vaporize some folks and their cars, nothing will every be bright enough to provide ultimate safety from stupid cagers.