Rechargable LED Headlamp

by Mike Nelson

16K4811

Intro: Rechargable LED Headlamp

First Instructable :)

I am a Caver. I love to run around underground. I also like to tinker with LED's (mainly inspired by Dan's instructable Ultimate Night Vision Headlamp

This is the third headlamp i have created, and the first i think might be worthy to post

Oh yeah a description, This is a LED headlamp made with 3 3.7V lithium batteries and 2 ~4 watt Cree Q5 LED's. The led is driven by the same device as Dan's headlamp, a 3021 BuckPuck from luxdrive.

STEP 1: Supplies!

Gather your supplies.

I bought/gathered my stuff from a few differant places

DealExtreme.com
- 2x Cree Q5 LED
- 2x Reflector
- 6x 18650 Lithium batteries ( they come in packs of 2, so i got 6 total)

Radio Shack (some capitol purchases here.)
- Mini Tool Set
- Soldering gun
- Wire
- 9-volt battery leads
- 3" x 2" x 1" project enclosure

LedSupply.com
- 3021 BuckPuck driver (the 1A version)

My Dad's Shop
- Curly cable from a cell phone car charger
- ~2 inch Aluminum heat sink
- Thermal Grease
- cheep headlamp strap
- Curly cable ( i got mine from an old cell phone charger )

STEP 2: Testing

This round actually matters. How bright do you want your light to be? how many settings? what kind of batteries, how many? so i got out my old breadboard and played around for a while.

I got a set of reed switches to play with (they are really cool), but ended up going with a double pull double throw switch from radio shack.

STEP 3: LED Casing

You have to protect these led's when they are driven for any amount of time with more than a couple hundred milliamps, so we found an old heatsink and cut it down to size. finding one can be annoying, and finding one small enough can be too... my first one i used a big CPU heat sink, the second one a big H - shaped alinum rod.

once you have it, drill holes in it where you want the led's to be to hold them in place. goop up the bottom of the LED's with thermal grease, stick them on and then screw them down.

Now the fun part.. solder them together. they are close, so fine work is required... make sure you hold the wires down when you solder them, cause if you dont, they will get in the way of the reflectors which are gonna sit directly on top of the LED's

once the solder has dried, cover all the circuits ( EXCEPT the lenses of the LED's ) with hot glue or RTV. this helps to hold them in place, and to protect them. Next, place the reflectors on the leds how you want them, make sure they are level, and glue them down.

STEP 4: Main Body Constrution.

Building the main body of the system, driver, switch...

This step involves taking everything off the bread board and shoving it into a small box...

For cables that have to move around, go to Savers or Good will and get an old cell phone charger with the curly cable design. cut it up and use it for stress/strain relief. I didn't do this on my first light, and the leads broke... course that one uses a 3 foot extension cord from Target...

Battery Pack:

fully charge all the batteries first. solder them all in series. solder wires about 2 inches long to the remaining positive and negative leads. get out a mutlimeter and make sure the reading is around 12.5 volts (full charge they are at 4.2 V ).. if not check your wiring...

once the wiring is good, solder on the 9V battery lead.

BIG PART HERE: i used a 9V plug for each end of the connection, so make sure you don't wire them up both the same polarity, or your light wont work. i soldered the 9V to the curly cable with the red leads being positive, and the black being negative. This meant that the negative prong was the smaller of the two. so on your battery pack, make sure the negative lead is wired to the BIG prong on the connector. this took me a while to figure out :(

Charging the battery pack:
I bought a universal smart charger from batteryjunction.com that can handle 1-4 lithiums in series.

STEP 5: Final Steps

Put it all together.

Hot glue the project box to the headlamp strap.

Secure the battery pack to the back of your strap.. notice I haven't done this yet..

its currently in a load testing session, its been on for two hours on the dimmer setting, and its still doing fine.. judging by the battery ratings i should get around 10-11 hours on low, and 2-2 1/2 on high power.

I will update this with what i find out, and upload some videos of the thing in action.

NEW: Video added showing the differences between the OFF, DIM and FULL settings.

Load Testing update: I ran the lamp on DIM for 12.5 hours and the voltage drop was around 1.1 volts. if this holds, the DIM setting should last just over 35 hours on a full charge.

More Updates:

I was caving this weekend, and I was underground for around 12 hours, and had the light on Dim for most of the trip, I would sometimes turn it on full blast to see all the details of the stalactites and other pretties on the ceiling.

I started a load test tonight on the HIGH setting, and after running it for ~15 minutes the heat sink was way too hot to touch and the hot glue was starting to melt :(.. I am going to investigate a larger heat sink, and using Silicone RTV in stead of hot glue to secure the reflectors down...

more updates to follow!

11 Comments

Zen Innovations 6 years ago

how to charge these batteries? What about load/charge balancing?

Mike Nelson 16 years ago

@dan They are built in to the batteries, the ones that shut them off if they get below a certain voltage? (these drop off at about 2.5 V.) cool thing is if lithiums don't work out, i already have a 6x AAA setup that plugs into a 9V slot, and i can setup a 6x AAA one just as easily. it also runs off of a single 9V, but I'm guessing not much more than an hour or two on dim... those things can't hold too much. @ahicks As far as a fuse, I'm only drawing 1A out of it, do i really need one?

torrent99 14 years ago

Yes you still need a fuse! It's in case you accidently short the things. Otherwise they have a nasty habit of going BANG and then catching on fire!

As for the Low Voltage Cutoff (LVC) circuit that Dan mentions, the 2.5V in your batteries is a bit low and might shorten the life of the cells. However, luckily it looks from your description that the light might cut off by itself before that which is great! Just watch though that you don't leave it on once it's cut out just in case the buckpuck still tries to suck some small current out which drains the cells.

Looks good though...nice instructable.

rondos 14 years ago

not a good idea to solder batteries, look for a holder. think personal safety. nice instructable.

Mike Nelson 16 years ago

After running the light for a 4 hour session on DIM and a 3 hour session on dim (both on the same charge) the battery has dropped from 12.6V to 11.9V. would i be correct in assuming:

.1V drop per hour
minimum voltage needed: 7.4(lights) + 2(driver) = 9.4V
life span on dim = 12.6 - 9.4 = 3.2 / .1/hour = 32 hours?

makes me really excited to see how long it will last on high :)

any more comments will be greatly appreciated.

joejoerowley 16 years ago

Cool! Great Instructable! Thanks Joe

StrangeRanger 16 years ago

Standard cell phone batts won't work, or for long, they can't handle the current draw. Look into some R/C batteries. Some nice, small Li cells w/ built in protection circuits can be found. Price depends on how much capacity you want. j

ahicks 16 years ago

Nice instructions. Good job! One question: where's the fuse? Shorting Li cells can be very bad!

LinuxH4x0r 16 years ago

Very good job! I might do something similar, but I would use standard cell phone batteries.