Picture of Ultimate 18v Bike Light!
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Mountain Biking at night (or early morning) is a true blast.. Using headlamps has been the only real choice short of spending some coin on a true bike light (some of these puppies cost >$500!!).

While the lack of light never stopped us from riding, the glory of having a MEAN bike light was calling me out.

The main problem I found with all the bike lights out there to build was the battery and housing.

  • Recharge battery packs cost some money and having another charger in the house was something I didn't want.
  • Housing is always an issue with DIY projects. I think 95% of my dads circuit boards lived in little blue hobby boxes. Sure they worked but didn't look so hot. I didn't want my new bike light sitting in a big ball of black tape.

The solution was to use the housing I found from the instructable: BIKE LIGHT 500 Lumen "Mt.Bike" for under 10 bucks by Veggiecycle -

This gave me a pretty good looking and durable housing but what about the batteries? The answer was already sitting in my charger!

1 18v Ryobi Battery Pack


I had already bitten off on the 18v series. My collection consists of the drill, saw, dust-buster, chainsaw (yup) and light.

This light is the one that we'll be using to create our 18v monster.

QUESTION - Why not just use the light that came with it? My friend tried this and it turns out that while the 18v light does give off OK lighting (and lasts awhile) it doesn't even come close to what we are building here. When you're doing you'll see what I mean.

WARNING - please please be aware that the bulb we are using here is a 12v NOT an 18v which means we are pushing (beyond) the limits of this bulb. This is a risk from a heat+safety standpoint. You can reduce the volts using various methods (one that I'm exploring right now) but in this project we push the 18v straight to the bulb.
WHAT?? no beam shots. please put some up!!!
Shinta7866 years ago
Hi, could you please also show a picture of the light working? Nice project tho, I have also a 18V battery on my bike, but I am powering LEDS. Halogen is better I guess. What would you prefer, halogen or LED? Thanx
Crash21088 years ago
Ball cock shank. Must... Resist... Joke...
lolomgwtgdairyqueen lolomgbbTHEq
only 1.65, whatadeal!
douglas.mauro (author)  Crash21088 years ago
Ugh... I knew that was gonna give me trouble :) I should have photoshop'ed a diff name in.
Mr. Rig It7 years ago
So is this thing bright or what?
dlfynrdr7 years ago
I cheated and bought an old nightsun lighting system for my light base, but I needed a battery. That's where I used this idea. I was lucky, I had an old no-name brand drill that was exactly 12 volts, so I don't have to worry about burning out my bulbs. What makes this solution for holding the battery in an old water bottle is the fact that it leaves a lot of extra space in the bottle for a small tool kit. I have a patch kit, some allen wrenches, and several screwdriver bits stuffed in mine. Just be sure to put them in a little baggy, so you don't have to worry about shorting any wires.
maker127 years ago

got to luv harbor fright!

12.88 for batery and drill Ni-cad dont know what the other one is made with, Great plan I have the light but was looking for a 18 v system
I am considering making this light with the 18v mod. However I have concerns about heat and battery life. I have this same Ryobi battery and charger. Could someone please report how long it will run on one charge? Also I know that 20watt bulbs run hot, and overdriving them can only make them run hotter. Is heat an issue with this setup? Thanks in advance! Nick
The battery will last for 40 minutes of bright light Heat is not an issue with a metal light housing as long as you keep moving. I'm not sure how the plastic one would do that is detailed here. A 5000 hour bulb will only last 25 hours with this setup. I've been on about 10 rides totaling 7 hours without a blown bulb. I'll report what happens when a bulb finally blows. Hopefully it wont be too destructive.
Thanks for the reply. I would need at least 2 to 3 hours or run time from the lamp to make it feasible for me. My average ride lasts 2 hours (or more)

I am still building the light but will step down my volts a bit to get some more run-time. Looking at this battery as posted in the VeggieCycle thread.
jdogg8 years ago
I set up my light (a simple malibu landscaping 12 volt spot light) with this battery system tonight. Loved it. Rode for 40 minutes at 20mph and the first battery back was still going string. The light is REALLY bright. Just be sure to bring a back up light and a spare bulb just in case.
Daedalus8 years ago
the light i made is waaaaaaay better then any thing you can buy or i have ever bought. i use a small 12v 7ah lead acid batt shoved in a large stash bag on a 50W halogen bulb to solve the current problem. I only ride home at night on tuesdays from work- luckly on a tuesday i dont have to bring my laptop and other CArp so its a comprimise on weight to the rest of the week. i do have a problem though cars dont like my super high beam!! and they make it VERY clear even if i dip the light ive even changed to a smaller watt bulb still dosent help can u?? (i originally used super bright LEDS but these were even worse{ even brighter)- they only ran off 6V nicd!!
I had been keeping my long broken Ryobi drill around thinking I could use it or some part of it for a project, and did basically the same thing to power my LED bike lamp project. I have it running 2 3w LEDs through a buckpuck and it runs long and bright. It's similar to other LED bike lamp instructables but with my own twist on the enclosure. Nice work.
mark1018 years ago
These Halogen lights consume way too much current to be used practically. Might as well buy a 12 volt car headlight and use that.
spacenookie8 years ago
You have to take apart a flashlight to make a bike light. Which is cool but what I would really like to see would be some kind of instructable on making custom battery connectors for power tool batteries, e.g. with cardboard, tape and copper strips.
Seriously, power tool batteries are durable, affordable, and ubiquitous. DeWalt and Ryobi are both adding all kinds of tools to their 18-volt lines, so those look like the targets to hit for the moment. Personally I'd like to see a "reverse" button on the in-vehicle charger, so I could dump a few power tool batteries into a dead car battery to start the car. ;) As far as building your own connectors goes, it doesn't look hard, you could probably make some progress in a weekend. Let us know what you find!
nice project...how long will this run on a full charge?
gargamello8 years ago
I also use a 12v 20watt halogen in my DIY light. My first housing was using PVC and other plumbing fittings. My original battery was a 4amh lead acid battery ($5.00 new). It was a decent rig, gave me over an hour burn time - but it was too heavy for daily commuting. I splurged and got a 7amh lithium ion water bottle battery from batteryspace.com, and also resorted to using a small gladware container for the housing. Changing these parts out save 4 lbs - which when you pedal 20+ miles is appreciated.
tomtiki8 years ago
See step 4...it is not advised to drill a hole in something you are holding, especially when drilling on a concave surface. It could slip and put a hole in your hand. Otherwise, very slick. I like the idea of repurposing the drill battery by using the flashlight casing. No special charger required. Now if I could think of something to do with my old Black and Decker tools (drill, light) that used those craptastic VersaPak batteries.
klee27x tomtiki8 years ago
Hmm, maybe something like this?
This screwdriver USED TO use the Versapack battery...

Now it runs on 3.6V x 4,400 mAh li ion battery.
justing tomtiki8 years ago
concave surfaces aren't so bad, it's the convex ones that cause trouble.