Added on Sat 28 Jul 2007
So you’re thinking of making bike lights?
I thought I would add yet another page to the many dedicated to the art of building bicycle lights. But before I dive into it, a little background on where I’m coming from when I first approached this.
Since the day someone accused us of entering the Mont 24hr bike race a few years ago, I realised that between Amirah and myself we would need some decent lights. The sort of lights you can race down a single track at 3am and not be left arhh… in the dark? Well, hoping to come across someone with proper lights, so you can follow them like a shadow, cataloguing every rock and root that passes briefly through their nice light, before it passes into darkness heading for your front wheel.
Anyway, with that in mind, I had a decision to make, I could either go out an buy two pairs of bike lights from the shop which (if they’re to of any use at all) cost a fortune for what you originally think should just be a globe, switch, wires and battery. Or make our own! I can say in hindsight, if I was making lights for just one, I would seriously consider paying the money for some off the shelve lights; on sale perhaps. However, we were 2, and that ultimately swayed me in the direction of making our own.
First stop was web research, what you’re doing now I guess. Like you probably have, I found many many website that show you various ways of doing this. You didn’t? Well there are a bunch you can get to from Mike Bentley’s page. Sorry, there’s a number of dead links in there though.
So far so good, but what did I learn? *************************
What it comes down to in my opinion are these main points. (I’ll assume that you’re in a similar position, to me, you basically need strong lights to last hopefully longer than a couple of hours).
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The globe, wires, switch & little bits cost nothing by comparison to the batteries and charger.
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Those expensive lighting systems are expensive for a reason. DIY versions using the same technology will cost a lot as well.
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You can sacrifice some performance and save a fair bit of money and trouble.
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Since all the parts you need to go out and get all have to work with each other, every decision you make will have a bunch of flow on effects.
I have to start somewhere, so I’ll start with the globe. You’ve got 3 options, LED, Halogen and HID.
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LED - low energy consumption and brighter than you’re expecting.
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Halogen - fair bit brighter, only average energy efficiency, but cheap.
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HID - brightest, good efficiency but a lot more expensive.
In simpler terms, I would say it basically comes down to 2 types. Everyday light technologies (LED’s and Halogens) and high tech light technologies (HID).
Breaking down the everyday option, you have longer burn time LED’s vs. shorter burn time Halogens which are generally brighter, easily accessible and cheaper again than LED’s.
There’s also the voltage to consider… but I don’t think there are many other options to consider but 12V. So many things are set up for 12V, you would want a good reason not to use it… and I can’t think of one.
Next comes batteries, here again, it’s another case of get what you pay for and none of them are perfect. Aside from availability, let’s look at each in terms of performance.
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Lead Acid - weighty (lead!) and large, but cheap and long lasting.
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NiMH (Nickel Metal Hydride) - lighter, fairly long lasting and resilient.
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Lithium Ion or Polymer - even lighter, but less resilient (when DIY) and more expensive.
An important note for the Li-Ion batteries… you have to learn how to look after them! Actually, same goes for all batteries. Go to the Battery University and find out all about it. For instance you can’t run them down to zero voltage like you might do with a NiCad or NiMH. What that means is your bike light might be quite bright, but you may well be in the process of killing your Li-Ion battery. It has a ’low’ voltage limit you should NOT drain past… do that and it’s probably the last time you’ll ever use it. What I’ve done is build a little voltage warning alarm that goes off below a certain voltage. The other thing is that all these batteries at full charge (but esp. the Li-Ions) have a much higher voltage than their rated voltage. The 14.4V Li-Ion laptop battery I’ve got here charges up to about 20V at full.
Finally there’s the charger. This flows directly from your battery decision. The reason is that each type of battery needs to be charged in a different way. So you can either get a specific charger for the battery type you pick (battery specific chargers are cheaper) or a multi-purpose charger that can do them all which are naturally more expensive.
If you want to build the ultimate system you would go straight for the HID globes (which also require a special electrical starter to go with them and typically costs as much as the globe) the Li-Ion batteries and the super fast Li chargers. However, you’re going to spend a fair bit on money doing that, for instance $200-$300 for the HID globe and starter package alone. So it is worth while checking out the top end systems your local bike shop, on ebay or wherever. You may find spending a little bit more might be worth while to have a ready made one.
On the other hand, if like me and you’re likely to be happy with a better than average set of lights for a less than average price, then fine read on and see what I ended up doing.
I decided that to start with I would use Halogen lights specifically MR16 and MR11 types, since they’re easy to get and cheap! Plus they have the added benefit of being fairly flexible with regard to voltage. The interesting point here is that an over powered Halogen is actually more efficient than one operating at a normal voltage. They’re not all rated with higher voltages since they have a significantly shorter lifespan when they’re over powered. I mean, my halogen globes may only last 5000 hours in its overpowered state… instead of say 25000 hours, obviously a big concern for me!
Next I decided that I wanted flexibility in the type of batteries I could use. So in fact the next decision I made was about a charger… I basically went out and got the best charger I could find. The MAHA MH-C777 PlusII was the one. I got it from the US for a very reasonable price and now I can charge any and every rechargeable battery I am ever likely to own! Ok, so it won’t charge Lead Acid, but that’s not a problem for me… oh and just make sure you get a proper transformer for it.
That left me free to find batteries from anywhere and be sure I could charge them. Hence, I’ve been able to tap into a second hand market of laptop batteries, which I would have never have gone into otherwise.
That brings me to the batteries. Second hand laptop batteries are great in many ways, but the downside is I have to break the battery open in order to use it. Obviously, that can be dangerous so don’t do it! But I did, and here is a photo of what you’ll face. (Click to see full size + select ”detail” once there to read a bit more about it).
The little bit of circuitry that comes built into many laptop batteries makes them impossible to charge outside of the laptop until, that is, you rip that bit off and hook directly into the main wires. Once I do that, the charger seems able to bring the batteries back to life nicely. I personally suspect that the circuits sometimes decide the battery is ‘full’ when really it isn’t at all. Giving the false impression that it no-longer holds a charge. While on batteries, a good set of NiMH’s can also be a fine choice. A little heavier, but you can run them virtually flat without fear of killing them.
Once you’ve got all the bits together, wires, plugs, switches and stuck them altogether - it’s then time to put them on your bike. Rather than go into too many details, I’ll let the pictures do the talking. Basically, I’ve gone through many versions. Mk-I, Mk-II, Mk-III & Mk-IV. My personal favourite is Mk-III, but I’m also happy with Mk-IV. The picture here takes you to the full gallery for all those, just make sure “details” is turned on and read the captions in the full view of each one.
Details aside for now, the underlying theme of all those goes like this…. Tube object to house the soldered wires, globe socket and switch. I’ve found that PVC tubes or as in Mk-IV – a flexible polyurethane (is it?) tube works well. A switch from electronics store and a clamp for the handle bars, then some sort of glue or bent wire to stop the globe from falling out.
For the batteries, some velcro strap (there’s a sort out that you just wrap around, no buckles… works well!) and find somewhere on your bike it won’t get in the way and basically strap it on! For a long time we used a sawn-off bottle cage with some rubber bands to good effect as well. One nice option is to make long skinny battery yourself and put them into the handle bars. Putting them in an under-the-seat pouch is also a popular option.
But it’s how we clamp the light to the handle bars that forms the most interesting challenge. I’ve normally gone for the boring option of using a hose clamp. But more recently I’ve decided to use a film canister that gets attached, which in turn holds the light. Which lets you attach the canister in a more permanent way. I used a simple cable-tie first time around, but I’m looking out for a better option for those next time.
In Mk-IV as you can see here
I’ve used the tube itself to fix it to the bars. This was an idea that sounded nice, but was a bit tricky to put into practice. As it turns out it’s a fiddly thing to hold and strap up at the same time, maybe with a bit more practice.
The latest idea I’ve been put onto, is to cannibalise an old bike light for its fitting… and glue/clamp/solder/tape your light onto it. That’s good too if you have one spare. In my case, my old lights are my ‘old lights’ due to the fact that the fittings have broken. So.. little joy there.
The future for me will be to buy some bright LED’s that come in the MR16 and MR11 form. It will be a dead simple job of simply replacing the Halogen globes with those… or running one of each if I want. Before those came along you had to build you’re own circuit to properly manage the individual LED’s, way too much work.
Well I hope that has been of some help to someone. If there is something in particular you would like to know more about, just let me know… I’m happy to go into more detail where you want.