corrado33

I'm sure this question has been asked over and over again. But, my case is a bit special.

For a bit of background, I currently have a fenix BT-10 for commuting. Recently there has been some road construction that has forced me to ride on a dirt road in the dark. I now know that the measly 350 lumens coming out of this light aren't enough.

I'm very electronically inclined. I love to build robots and other small electronics projects.

I was debating using a battery backup battery (12V, roughly 2.5x4x4inches) in a waterproof container to power my lights, using various voltage regulators to get the voltage to what's needed for various lights. Designing such a simple power distribution board would be extremely easy for me.

The advantages of using a battery with a power distribution system:

• I can use any light I'd like
• It'll work just as well when it's raining.
• Full brightness standing still.
• Don't have to worry about it messing up my tire.
• Cheap (I already have all of the parts.)
• Don't have to rethread wheel (hub dynamo)
• Can use battery to power heated gloves (if necessary.)
• Reliability. It's a battery, those usually ARE people's backups.
• Can use it to heat it's own compartment (if necessary) to deal with cold days.
• Could possibly use it to charge things (devices) (not that I'd ever do that, but it's possible.)

I'm not going to use a hub dynamo for a few reasons. Cost and complexity. This is going on an OLD bike. It's not worth it to rethread the wheel. And I don't feel like spending 2-300 bucks on a decent hub dynamo.

I did notice today that the tires I installed on the back of this bike have the ridges to work with a bottle dynamo.

Therefore, if I got a CHEAP bottle dynamo, the ones that like to blow up bulbs. I could simply regulate it and use it to charge the battery, but not to power the lights. (Sure it'd technically be doing a bit of both, depending on how I made the circuit.) It'd still have to deal with the bottle dynamo potentially ruining my expensive studded tires however.

As for weight, this battery isn't much more heavy than a normal book I'd tote back and forth from work to home, so that's not an issue.

Thoughts? I could use any normal 12V bulb/housing made for dynamos (which are generally extremely cheap!) Or I could power my 5-6V bike lights (that normally run off of 4 AAs). Voltage regulators are extremely cheap (even the high power ones.)

EDIT: I also ENJOY doing projects like this, so even if it's not perfectly practical, I may still do it.

fietsbob

if thats your CV, I'll just watch you work it out for your self .. robo engineer I'm not.


Seems bike lights have stayed 6v for a long time, I built a 6v battery pack using 5 1.2v D cells in series .. 25 years ago

bulb lights draw what they need from a battery , I suppose.. front halogen .. Union headlight reflector .. flange base bulbs came from Radio-Shack

had a 60 minute commute back then.

bconneraz

I love to tinker as well, but I spent way too much time and money trying to get "trick" with my commuter. I finally realized that a Niterider Lumina 750 made more sense for me, and I am delighted that I finally went that route.

PaulRivers

Fyi, you can buy an entire wheel with a Sanyo dynamo hub which several posters here have said work well (it's drawback is that it's a little lower quality, and turning it off doesn't actually reduce the very small amount of dynamo resistance from the hub) for $135, plus $5-$15 in shipping according to a quick search -
https://www.calhouncycle.com/productc...wcart.asp?cs=1

I just mention it because you mentioned "dynamo" in the title. Biggest drawback would obviously be cost, as one would also need a light to go with it, which would cost around $110 for a good one.

The cheapest route is to buy 2 cheap but high lumen output lights off of amazon. Carry both, if 1 fails, use the 2nd one.

I like the Phillips Saferide as it has a shaped beam, but it's more around $150 total. It's the light I most recommend to friends and family though, best light for road biking I've found so far.

noglider 

I can't comment in your overall idea, but I will say that bottle dynamos don't really suck much. I've been putting antique ones on bikes lately, and they work fine. They are powering modern LED lights, which don't blow when the input voltage goes up.

krobinson103

Tried the battery trick. Its really not as good as you think it might be. A small 5ah scooter battery will run a smart phone via a usb adapter for about 12 hours with the screen on. Thing is it takes up more space than its worth. I've switched to liion cells with a charger/discharger and a solar panel. Then I use 300 lumen torches on the bars that use the same cells. I get gadget charging, off the grid capability, and batteries I can use as a light source if I want to. Its been bouncing around in head to take a bottle dynamo, mount it to the brake track (I use discs) and draw power from there. But, I think its easier just to get a hub dynamo.

noglider 

I have the supposed worst dynamo hub, the Sanyo. I can feel the vibration sometimes, but I cannot discern the drag at all. I know it's there, but only because I know it, not because I can detect it. I have one on two bikes. They work great.

I'm lucky that building wheels is easy and fun for me. If you can't do it yet, there are many people here on bikeforums who would love to walk you through it.

unterhausen

wheels are expensive, no doubt. But they last a long time and a hub dyno means you never have to worry about charging batteries. I find that really annoying. And you also have to figure out where to put the batteries, which is also annoying.

I am an engineer with good fabrication skills, and I just find making lights not to be worth it. If I make a robot and it has a failure, big deal. If I'm out riding and my light goes out, that is a big deal. I have had this happen because the glue I used for an emitter failed. Thought I was going to have to walk 7 miles.

I agree with Tom, I would probably use a bottle dyno. They are a little loud, but I've never had any problems with one even in freezing rain

tarwheel 

Hey, if you like to tinker, go for it. However, LED lights have become so inexpensive that I doubt if you would save much money. You can buy a quality self-contained LED headlight -- that is, with a built-in rechargeable battery -- for prices ranging from $50-125. Eg, I recent bought a Light & Motion Urban 800 for a little more than $100, and it puts out 800 lumens on high, 350 lumens on medium, plus it weighs only about 120 grams. You can buy LED flashlights with 18650 rechargeable batteries with comparable outputs for even less money.

The situation with LED lights now is comparable to wheel building. If you like to build wheels and have the skills and equipment, you can build yourself and excellent wheelset -- but it is likely to cost you as much or more than buying a prebuilt or custom wheel with the same parts.

noglider 

That's a good analogy between building wheels and light sets.

I recently bought a little voltage regulator which is half the size of my thumb. It has a USB jack. I got it directly from one of those Chinese vendors. I might have gotten it on ebay. As soon as I got it, the vendor wrote to me asking for feedback on how well it works. I may never use it. I got it as a curiosity. Maybe I'll try to build something with it. I'm not even that inclined, electronically.

corrado33

Thanks for all the information guys.

The main reason this first popped into my head however was NOT for a light, but for heated gloves. I then expanded it to the possibility of also using it for lights so instead of having to worry about batteries for my lights and gloves, I'd just have to worry about one larger battery.

I may try it, if I do I'll post pictures and let everyone know how it works out!

noglider 

Please do share your results!

Mr IGH

Is 3W enough to heat two gloves (1.5W for each glove)?

Robert C

I have a dyno-hub on my bicycle. A couple of days a go, as an experiment, I also put on a cheap cree magic shine clone.

There simply is no comparison, the cheap (about $15 for the light and another $5 for the defusing lens) worked better in all ways. I suppose that if I had a three or four hour commute I would have to worry about the batteries giving out; but with my 15-20 minute commute that is not a concern.

The cheap light had a good cutoff (with the defuser lens), and unlike the dyno light, it filled all of the lighted area. The light was significantly stronger and wider. Even on the "low" setting the cheap light was strong enough that the effect of the dyno light could not be seen.

The dyno light has a place. as a permanent part of the bike it serves as a "minimum legal requirement" light for when I forget the good/cheap light; but, as far as quality, as a headlight, there is just no comparison. Save a coupe hundred dollars, get the cheap one

ItsJustMe

I find that I need heated feet more than heated hands.

Last year I experimented with putting some nichrome wire between a couple of sheets of kapton tape and hooking the whole thing to one of my 7.2 volt 4 cell (2s2p) cheap LED packs. It worked very well, it turns out you only need about 8 or 10 watts per foot to keep toasty warm even in very cold temps (below zero) wearing mountain bike shoes.

IMO, buy a cheap < $30 light for a headlight, then play around with other solutions for the gloves/feet - I would NOT want them tied together personally.

I'm with Robert C on lights - a $30 battery/LED is brighter than any dyno system on the market, and since it sounds like your commute is a bit like mine - gravel road and sometimes very rough pavement with sometimes a 10 inch wide safe path between tire-destroying potholes and cracks, you can't get away with a mediocre light.

Oh, and on the heaters, fuse that thing. It's going to be on your person. You will NOT be happy if you have copper wire running from your waist down your legs (or up your torso and out your arms) and the heating element shorts out - there's enough current to make the wires really damned hot, possibly hot enough to melt fabrics that are up against your skin. The LiIon pack will have a polyfuse in it, but it can still put out 2 or 3 amps, enough to make you really unhappy.

mrbubbles

So true. My dual cree xml light is $50, outshines my DIY dynamo lights by far (and my DIY dynamo lights are already brighter and floodier than the best commercial dynamo lights available). Plus the $50 is movable from bikes to bikes, and is helmet mountable, also can be used as a headlamp for non-bike duties. That said, I'm still gonna use my dynamo lights (and I have 4 bikes equipped with dynamos and dynamo lights, cheapest being an Shimano LX dynamo).

corrado33

Apologies for not making myself more clear. I had intended on using prebuilt heated gloves generally used by long distance motorcyclists. Hence the want for a 6 or 12V battery. Therefore, it shouldn't short out, unless that glove company wants some very, very bad reviews. You can buy the gloves by themselves relatively cheaply, ~50-100 bucks, but gloves that include batteries are generally 200-300 bucks.

PaulRivers

Is this going to descend into another dynamo vs battery debate thread? I would agree that dynamo lights from 5 years ago were poor for riding, but that the modern dynamo lights are far superior and very good. They're as good or better than any of the battery lights I've tried, because they do a far better job at distributing the light. But is this really the place to debate this when the OP has a desire for other battery uses that mean a dynamo wouldn't work if he wants heated gloves anyways?

corrado33, I've only heard of a few people trying to use heated gloves on a bike. Usually there are a few reasons why heated gloves are not used on bikes:
1. You're not going as fast as you would be on a motorcycle, so far less wind against the hands
2. You're exercising, so your body produces heat
3. The problem you're running into - the bike doesn't produce power by default.

I would suggest two things:

1. If you're willing to hook up a battery with a cable, then consider bike-specific gloves that attach to the bars like these:


2. If you do want to go the heated route, consider that you'd probably be better off with a second battery inside your jacket. In addition to the trouble of attaching yourself to a bike with a wire, all batteries perform worse in the cold - they don't last as long, and they have lower capacity as it gets colder. With helmet lights it's frequently recommended to keep the battery inside your jacket where it's warm as the battery has higher capacity when it's warm than when it's cold. It would make more sense to me to find a way to run a wire through each arm of your jacket to the gloves, attached to a battery inside the jacket, then it would to try to use 1 battery that's exposed on the bike for everything.

corrado33

Paul: Thank you for the suggestions. I already bought some Dogwood Designs pogies for this winter, I'm waiting until it gets cold enough to try them out! (Super long fall here in MT this year.) As for you other suggestions, I'll get to them shortly.

Also, people may or may not remember, I believe I have some sort of circulation problem in my hands. They get MUCH colder than they should when I'm riding my bike. Colder to the point where I'm in pain by the time I get to work. This is the reason why I'm putting so much effort into keeping my hands warm.

Well, I breadboarded a small circuit using a linear regulator to drop the 12V down to 6V for my BT-10 light. One thing I realized. I will not have to worry about the battery getting cold. In an sealed enclosure that's somewhat insulated, the linear regulator with heatsink will be dumping up to 6W of heat into the surrounding air. (Assuming that I'm using 1A of current, which I'm not. The BT-10 uses ~650mA at it's highest brightness.) That's quite warm. I actually think I'll have to ventilate the battery enclosure to make sure that the regulator doesn't overheat. For those of you who know electronics, I want to use a linear regulator for this reason (to heat the enclosure.) And it's what I have lying around the house.

Secondly, I'm debating making "battery powered hand warmers/pogie pre-warmers." Basically a small fabric square that has some NiCr wire running through it and I can pass some current through it to heat up my pogies before I get ready to leave. Flip it on 5 minutes or so before I leave then flip it off when I actually do leave. I think it'd be cool. (Pun partially intended?) I was already going to warm up the pogies with a hair dryer before I left in the morning. This will be quieter and more convenient. I think people would look at me weird if I was hair drying my pogies at work.

I realize that what I'm trying to do can probably be accomplished easier using other methods, at this point I'm just doing this for fun.

On another note, I e-mailed Fenix asking for their maximum safe operating voltage for the BT-10 and BT-20. I wonder if they'll ever get back to me.

unterhausen

pogies are often too warm in even the coldest weather, so this stuff may not be necessary even with Raynaud's. I probably wouldn't use a linear regulator, there are really easy to use switchers nowadays and a linear dumping a lot of heat isn't the most reliable object around.

corrado33

True, I was debating switching to a 2 cell Li-Ion battery to cut the wasted head down from 6W max to 1.4W max. (At 1 amp.) I'm going to run by the battery store later, we'll see what I can find. I'm trying to do this without purchasing anything besides a battery (if needed.) I have some old SLA batteries, but I'm pretty sure they're 3/4 dead, so I may have to buy either a new SLA or a Li based battery.

PaulRivers

Gotcha.

Is this a winter bike only project?

My one thought there would be a concern about frying the battery with heat in the summer if it isn't.

Good luck. :-)

corrado33

Yes, it is a winter only project. I don't need a light (or heated gloves) in the summer!

EDIT: According to a dubius looking datasheet on the BT-10, the max input voltage is 12.8V.

https://manual.compegps.com/manual/FENIX_BT10.pdf

This is great, it means I can not waste nearly as much heat in my regulator. I still want to regulate it down to maybe 7-9V, as running things at their maximum ratings for extended periods of time isn't a good thing. And besides, a regulator is maybe a dollar or so, while the BT10 is (now only 50-60 bucks). It was over 100 when I bought it.

This is great, now I can manage the heat much easier!

corrado33

Well, I made a circuit. Even added a low battery indicator! I'll build it up tomorrow and see how well (or rather IF) it works.

For those of you who'd like to know. I'm using three linear regulators (mainly because I have them sitting around my desk.) One provides 9V (adjustable 12-6V) to a front light. Another provides 9V (non adjustable) to a front light and to a third regulator, which will provide X (adjustable 9-1.2V) volts to the rear lights. We'll see what light I use. There are wire connectors to attach the lights to. (Or rather, to attach the external connectors to, so I can simply plug/unplug them if I'd like to remove the box/light.) I plan on buying another BT-10 or BT-20, hence the two different front light outputs.

Hmmm, just thought of something. I should REALLY add an on-off switch...

I don't think I'll have a problem with heat. I cut the wattage of heat in half, and I can fit a hell of a heat sink in there, so I think I'll be fine.

I'm no electrical engineer, so I'm probably doing a few things wrong in the circuit, but the individual elements worked on a breadboard, so we'll see!



EDIT: Power switch added.

noglider 

Ooh, let's see. Pictures!