DIY Insanely Bright LED Bike Light With LED Strip Lighting (on a Budget)

The people who design LED bike bikes never use them, or design them simply to sound good on paper, I swear.

Popular bike lights have a million pointless options for different styles of flashing, and every time you turn them off, they turn on on the next setting, so if I only want to turn them off for a few seconds to not blind a passerby, I have to find the mess with the switch and go through the whole cycle again which is incredibly annoying. I also find that the vast majority of bike lights allow others to see you, but don't light up your path well enough for biking safely in the city, not to mention trails.

Biking is also how I find parts and materials for my projects, and I never have enough light when taking apart the things I find, and being able to simply point the light at what I want to take apart would help me tremendously.

Let's not even get started on rear lights!

In this Instructable, I will show you how to make the ultimate bike light that solves ALL of these problems - front AND rear! To make it, I ended up spending only $25 in parts, but it took me 2 years to design (solve 1 problem, 3 arise!) and 1 week to build, so for a different bike it would probably take you 1-2 weeks to make a custom design, and 1 week to build it if you spend several hours working on it every day.

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(Don't want to read the I'ble? Watch the Youtube build video and see it in action!)

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My bike: Marin Bobcat Trail 4

My homemade bike rack (Instructable)

You might also want a bike stand to stop your bike from falling over constantly during the build.

For everything else you see on my bike, check out my Ultimate Bike Accessories Kit (everything I recommend).

Tools:

• Adjustable temperature soldering iron
• Flex-shaft rotary tool
• Mini drill press
• Hacksaw
• Cordless drill & drill bit set with a step bit
• Snips
• Multimeter
• Mini torch (for heat shrink tubing)
• My homemade soldering vise
• Proper safety equipment (Kit: the PPE I recommend if on a budget)

Hardware, Materials & Consumables:

• Square aluminum tube
• Rectangular aluminum tube
• 12v 20w LED (make sure they are actually 12v and not 36v)
• Lens and reflector for the 20w LED
• Waterproof red LED strips
• 3/6/9/12 18650 batteries (I got mine from a laptop battery. Don't buy cheap ones, they're filled with sand!)
• 3S 10A 18650 battery charger
• 3 2x18650 battery holders
• High speed LED dimmer
• 3 Button strobe dimmer
• Locking bullet connectors
• Gigabyte motherboard heat sink
• Thermal adhesive
• Aluminum flat bar
• Clear duck tape
• Silicone adhesive
• 15w LED pair (actually 1.5w)
• Stainless steel bolts and nuts
• Heat shrink tubing
• 2 Waterproof toggle switches
• Zip-ties
• Wires
• 3S LED battery capacity meter
• Tube end caps
• Aluminum angle
• 45°C NC thermostat (temperatures over 45°C open the circuit to cut power)

I've used dozens of regular 12V 10W LED's for my past projects, but decided to use a 20w LED for several reasons after comparing them.

10w LED's consume 0.9-1.2a @12v, and overheat without a heatsink after about 2 seconds. They may look easier to mount because they're smaller, but they require a larger heat sink, and small condeser lenses are hard to find.

The "20w" LED consumes 0.75a @12v (unless if my measurements are off, odd, I know), looks about 50% brighter and can last a good 30 seconds without a heatsink without any need for cooling. You can find lenses and reflectors for these easily, but it's important to keep in mind that most 20w operate at a higher voltage so it's important to not buy the wrong one accidentally!

I found a heat sink in my collection that fit right under the handlebars on my bike. After cutting off a fin (see picture 2) it was large enough for the LED, but just small enough to be mounted without touching the head tube. I glued on the LED with thermal paste.

After breaking my brain and trying to come up with ways to mount it, I came up with a simple solution that consists of a short piece of bent aluminum flat bar that slides in between the fins of the heat sink and secures to the headset spacers - simple!

When gluing things to my bike, I like to tape the frame with clear duck tape. This way I can remove the glue if I ever need to easily without damaging the paint. If only I had thought of this earlier!

These small LED's may be advertised as 15w... But they're 1.5w each, were sold with oversized hex nuts, thin wires, and one broke as soon as I tried to tighten it. So I would recommend using something else, but they're just as bright as I need them to be, so I don't see any reason to bother replacing them any time soon.

I drilled three holes in a small piece of aluminum scrap bar, two for the LEDs to be mounted to, and the other for mounting to the bike through the threaded hole in the bike fork. What I didn't think of is that when the fork compresses, it almost hits the LED's. So time will tell if they get crushed!

I don't know where I got this small piece of scrap, but this was the worst aluminum alloy I have ever worked with. It was so gummy I could barely drill through it, and when I tried to round the corners with my flex shaft rotary tool, the burr kept catching on it.

The bike rack I built last year (see my Instructable on it: DIY Bike Rack with a magnetic U-lock mount) is a crucial part of this project, and I designed it with steel angle bar specifically so LED strips could be glued to it.

The glue on the red LED strips I bought seemed to have failed before I even used them, so I glued them to the bike rack with silicone adhesive and added a few zip ties to make they stay in place.

This is where the complicated part begins. Ever since I starting designing this project, I focused mostly on the control box, testing dozens of different components. I tested regular toggle switches, rotary switches, many others, and eventually decided to use the one you see here for all sorts of different reasons that I thought made the most sense, but mostly simplicity and reliability, remembering my bike will be exposed to the elements and endless amounts of vibration while riding.

I decided that the 20w LED should be powered by a high-speed dimmer. I've used them for years and have never had any issues with them. This type of dimmer is very efficient so almost no electricity goes to waste, and unlike many PWM dimmers, it flickers (that's how these work) much faster so annoying flashing lines can't be seen on camera.

As for both of the LED's in the front and the LED strips on the rack, I wanted them to flicker at the same time and be powered by the same strobe/dimmer, but I wanted to be able to turn them on or off independently since I knew most of the time I would prefer biking with the red LED strips flashing behind me, and with the dimmable 20w LED that's on consistently, instead of with both of the 1.5w LED's flashing. This is because when biking in the city, the light reflects off of things and back at me which is annoying and I prefer to avoid it.

I also wanted to add a LED capacity (voltage) meter, so I could stop having to guess when I need to charge it, or end up in the middle of nowhere with no power.

To house all of the electronics, I decided to use a square aluminum tube that was slightly narrower than the top tube of my bike frame. Wiring the components after they were in the enclosure would be impossible, so I wired the switches (they had screw terminals so I glued them with CA glue to make sure they wouldn't unscrew due to the vibrations). The dimmer also had screw connectors, so I desoldered them and soldered the wires directly to the circuit board - every screw will unloosen given enough time! After bolting both of the switches and the dimmer, I passed the input wires of the switches through the hole I drilled for the output of the dimmer, soldered them together, and pushed the wires back inside. I then passed the wires of the LED volt meter through and glued it in place. Being left with the input wires for the strobe dimmer, dimmer, and volt meter, I soldered them together, and then to a waterproof female bullet connector which will later connect to the battery.

To put it simply, all of the components (except both switches) receive power directly from the input. The high-speed dimmer powers the 20w LED headlamp. The strobe dimmer's output connects to both switches, the left one powers both LED's in the front, and the right one powers the red LED strips. I recommend thinking through every part of the wiring process in advance to reduce the amount of wiring necessary. Every additional wire and solder joint is a recipe for making a mess in the future in case something stops working, and you have to take everything apart to find the cause. In the end, I have 3 pairs of wires entering the control box, and only 3 pairs exiting. I'm really glad I spent the time trying to minimize the number of solder joints and wires because it would've been a mess otherwise.

I then mounted it to my bike, protecting the frame with tape as I did earlier, and secured it with silicone adhesive and zip ties. Looking back I could've left the strobe dimmer inside the control box (so I could make it even smaller), since I don't plan on ever changing the settings again.

A quick overview - at this point the control board is wired and mounted to the frame, with three (output) wires waiting to be soldered.

I soldered the wires (which I expanded on in the previous step) directly to their LED's, but decided not to for the LED strips on the bike rack because I want to have the ability to remove the bike rack in case I ever need to for transportation or if it ever breaks. I wired the LED strips through a locking connector so I can disconnect them easily, as well as if some part in the control box (that I am unable to identify in time to repair) ever breaks, I know I can always power the red LED strips directly from a different power source. I don't expect any of these things to happen, but I don't like getting stuck in the middle of nowhere without any lights!

I like to leave a bit of slack in the wires (which I zip tie to the frame) in case I ever have to do repairs. I also sealed any exposed solder joints with silicone adhesive to protect them from the rain.

To finish it off, I zip-tied the 60° lens and reflector with the bracket that came with it. It's meant to be bolted onto the heat sink, but it was too small and this was the best thing I could think of.

The switches I bought also came with a rubber "boot" cover for waterproofing, so I added them as well as a knob for the dimmer.

I had square tubing caps that happened to fit the exact diameter of the control box, so I glued them in place after cutting off a few parts because the switches didn't allow it to be inserted. The aluminum tube I used for the control box had a hole in one side (I used this tube originally as a prototype for my homemade tripod) and I had to work around it, but in the end everything worked out.

Now, to build the battery!

It took me a long time to weigh the upsides and downsides of all of the possible options for powering the bike light. I could power it with a drill battery, a lead-acid battery (which would be very heavy), build or buy a Ni-mH battery pack, or build or buy a li-ion battery pack.

I decided to build my own Li-ion battery pack out of 18650 cells that I got for free from a laptop battery. They would fit inside of a rectangular aluminum tube under the top tube of my bike frame. Being enclosed in an aluminum tube protects the cells from the elements, but most important of all, it's fireproof (in case of a charging accident) and is puncture-proof and impact-safe (in case of an actual accident), both of which are very important for li-ion batteries! Depending on your seat post, you might be able to fit the entire battery pack inside it, but I don't want to be left without power if it gets stolen.

This is my first time building this type of battery pack, and it turned out exactly as I had planned, but building battery pack like this one can be very dangerous if done incorrectly, so I won't provide step-by-step instructions for how I did it, since it's possible I missed important safety measures, and I recommend you do your own research. But basically what I did was group 6 18650 batteries into 3 pairs, and soldered them according to the schematic of the 3S protection board I used, double-checking a million times before and after each step to make sure I didn't make a mistake. I didn't have a spot welder which is what's typically used for building battery packs, and I read that soldering them directly can be dangerous, so I used 3 flat-spring-loaded battery cases instead. Don't use cases with spiral compression springs, they don't hold batteries properly and disconnect constantly.

After soldering all of the wires and making sure it worked, I inserted the battery pack into the tube, and made two aluminum brackets to mount it to the top tube with zip ties. The wires that pass through are for the charging input, output, and for the 45 degrees (c) thermostat that should disconnect the power if anything overheats. I miscalculated the size of the battery pack so I zip-tied one side of it straight to the frame, so I'll go back and mount it properly with a used inner tube to reduce vibrations as well ASAP.

Back when I built my bike rack, I intended to mount the battery under the bike rack between the U-lock mount, but I changed my mind because I prefer having the weight of the battery in the middle of the bike. I like to bike up stairs, and any weight I can get off my rear wheel decreases the chance I'll get a snakebite-style puncture. The battery weighs less than half a kilogram (<1lb) which is significantly less than a lead-acid battery, so I would've been fine either way in terms of weight, but what I realized recently is that the bike rack gets dangerously hot when I leave it out in the sun even though it's made of aluminum, and I prefer to keep it as cool as possible.

In total, the battery is about 75wh total, so it's comparable to a 12v 6a lead acid battery which weighs ONLY five times as much :)

Watch it in action, on Youtube!

I love how it turned out, I've been biking with it for the past few weeks and this is the coolest and one of the most useful projects I've made so far! I've been biking in the dark with mediocre lights for years and have always felt that drivers can't see me well enough - not anymore! And not only that, take a close look at the cement on the wheel rims - that's the result of what happened when my previous light wasn't bright enough and I didn't see the pool of cement before I felt it!

My favorite part is the red LED strips. First of all, they look epic! I was able to utilize all of the available space on the bike rack, so they're very bright and can be seen from far away, but don't bind you because the light is spread over a large surface area, unlike small lights. I think and drivers can see me more clearly now, and not only a flashing red dot moving in from of their eyes.

Most of the time I bike with the flashing LED strips and 20W headlamp on at full power, and the battery seems to last forever! I'm very satisfied with the result and it was definitely worth the effort! If you make any type of bike light based on this I'ble, please post pictures in the "I made it", I would love to see them.

Some more thoughts:

• All in all, I spent $25 to build it ($7 for the battery components, $18 for everything else). This was more than I thought (I mostly reused components I bought years ago for other projects), but this is still nothing for this kind of light.
• If you don't have a bike rack, I recommend buying a red 10w LED (or red rear-view mirror motorcycle LED's) to mount to your set post instead of the LED strips. This was my original plan before I thought of building my bike rack.
• Now I'm thinking of upgrading the LED strips with neon LED strips that look more consistent.
• If you have a large bike rack, you could even make the LED strips < and > shaped, and they could flash like indicator lights, like these, but much larger.
• I also thought of also having a USB boost converter inside the battery, this way I could charge it through micro USB or even through the 12V lines of USB-C, but this ended up being too complicated with different voltages, and the battery basically lasts forever anyway. This would only be useful in an emergency, which I have none, and I can always build a more accurate external boost converter to charge it properly through USB. I don't want to mess around with charging batteries that could cause a fire wherever it's avoidable.
• I also thought of making it solar-powered since I leave my bike in the sun for many hours every day while I'm at school, but they are expensive and fragile, and I don't have space for one on my bike. Though if I did, a USB solar panel would probably be the simplest way to make sure the charging is regulated properly, and I could also use it to charge my phone.
• Another idea I had was to glue LED strips to the sides of the frame to be more visible from the side. Check out these multicolor LED strips made for car doors.
• If you want to power a headlamp but don't need a dimmer, check out this handlebar switch made for motorcycles.

• One thing that bothers me is that the headlamp flickers slightly when I also turn on the red LED strips because they make the voltage of the battery drop slightly. But this isn't visible when I'm riding, only when the bike is stationary. I think a capacitor could fix this issue, but I don't know how exactly that could be done, and I don't want to damage the dimmer.

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