Most of the posts I do are about historical lights in my collection. However, from time to time I like to make a Maglite tech post as well, either about how the lights operate or about restorations methods and neat modifications. So for this post I'd like to share a light I recently put together myself as well as some lessons I learned about LEDs, drivers, heat sinks, and batteries. Please feel free to provide any feedback if I've gotten anything wrong. This is about the closest to creating a light from scratch as I'll likely ever get. One day maybe I'll have enough time to learn how to use a lathe but for now this has temporarily satisfied my flashlight building curiosity.
I get a few requests here and there to restore old Maglites, especially ones that have sentimental value. Most are true to the originals and leave my workshop with an incandescent bulb. However, occasionally I get requests for "restomods" or original looking lights but with modern technology inside. Up until now the best I could do was a Malkoff dropin. While Malkoff makes one of the best drop ins on the market they have a cool, blueish tint which is very different from a warm old school incandescent light and they are a single mode and very bright. I find myself most commonly using 30 lumens at night. So I decided to advance my limited electronics and LED knowledge and build a multi-mode warm LED drop in.
Driver
For those unfamiliar, LEDs have near 0 resistance, can only operate at a specific voltage, and vary their brightness by current or PWM. You need a driver board circuit to fulfill these requirements. Simply attaching an LED to batteries will likely cause it to be destroyed or it just won't light if the voltage isn't high enough. You could run it in series with a simple resistor but you'd have no way to vary the brightness.
There are many many driver boards available and they operate in a ton of different ways. For this project I need a 17mm driver and I'll get to why in the heat sink choice below. This is a very popular size and there are many options. There are 3 additional considerations when picking a driver.
1. Voltage
I chose a 3V LED as you'll see below so the LED really can't see more than 4.2V. Above 4.2V I risk damaging the LED and below 3V the light won't work. In this case I'll be using a KAI Domain 3V - 9V driver. This type of driver is commonly referred to as a 3V buck driver. It will lower (buck) the LED input voltage down to 3V so it has a far greater input range of 3V to 9V which means it can be used with anywhere from 3D to 6D NiMH or alkalines.
Another choice to accommodate this is a direct drive. In this setup the voltage the batteries provide is not modified, it is fed directly to the light, hence direct drive. Therefore the voltage range is very tight before it will either fry the LED or fail to light. The range of 3V to 4.2V coincides perfectly with either 1 Li-Ion cell or 3 - NiMH cells. 3 - alkalines provide 4.5V so they can't likely be used. This is a simpler driver and Adventure Sport makes one with more than 25 groups of modes otherwise they don't have many advantages over a buck driver.
Yet another choice is a 3V boost driver. It will step up the voltage so a 2D setup can be used. The input voltage on these is 0.9 to 3.0V. I plan to build some 2Ds as well so I'll be buying one of these for a future project.
2. Modes
I want modes for this project because the light seems to be a lot more versatile and useful with different levels of brightness. I'm basically looking to make a retro ML300L. Modes can be accomplished 2 different ways; either by alternating the light on and off more quickly than can be seen by the eye (pulse width modulation - PWM) or by varying the current flow (amps). Unlike incandescent bulbs varying the voltage will not work since the LED only runs at a precise voltage. I chose this KAI Domain driver because it has 3 modes, 5%, 30% and 100%.
The Adventure Sport direct driver has 25 groups of modes which make the light a lot more useful. This is a tradeoff though because it is direct drive so the battery options are more limited. There are multiple brightness settings settings and multiple strobe and moonlight modes so I'll be using the Adventure Sport driver on a future 3 - NiMH restoration.
3. Current
I want to pick out a driver that provides no more current than my LED is rated for. A common maximum current for Cree LEDs is 2 amps. I also want a driver that can deliver near 2 amps so I get the full output of my LED. Picking a driver that only delivers say 1 amp when my LED will take 2 is only going to give me a max output of 50% of the rated output. Running a 2 amp LED on 1 amp driver will only give a brightness of half of what the LED is rated for. This may not be a bad idea though if you're looking for a single mode light with a specific level of brightness. The KAI driver delivers 2 amps and my LED is rated for a max of 2 amps here.
LED
I want something that has a warm or neutral tint because it looks more like a classic Maglite and there's nothing on the market available. Obviously that narrowed it down some. My other criteria is that it had to be mounted to a 10mm board due to my heat sink limitations. Also, my driver puts out 3V and 2 amps so I need an LED that has a 3V forward (input) voltage and is rated for at least 2 amps. I am really familiar with Cree LEDs so this all narrowed it down to an XP series LED. The XP-Es are low output, low amps so I skipped right over those and went for an XP-G although an XP-L will work just as well. I went with an XP-G 3500K, warm tint for this project as that most closely matches an incan bulb. The XP-G is rated for 700 lumens at 2 amps so that will make a very nice high mode when paired with my driver. In fact I most commonly use the 5%, 30%, 100% mode group so my light will have 3 modes of brightness, 35 lumens, 280 lumens, and 700 lumens which can be accessed by quickly cycling the switch.
The toughest part is picking a heat sink to house the LED and driver. I have an old Adventure Sport light with a copper heat sink and that heat sink is the perfect size for a D cell Mag. I actually found out that Adventure Sport also sells an aluminum heat sink that is far less expensive (~$17) and that has dimensions more suited to my project. It uses a 10mm LED board so any stock Maglite reflector can be used with the cam removed. On the backside any 17mm driver board can be used for the LED. As far as I know this is the only option for someone looking to build a custom light. You could make one but I'd wager it would end up looking identical to this.
Shown below are the modifications needed for a stock reflector on the right, and a KAI Domain reflector with a detachable cam on the left. The blue plastic Maglite reflector all the way on the right has had the cam sawn off with a hacksaw near the base. The KAI Domain reflectors have a cam the screws off so they can be used with a stock light or with an aftermarket drop in.
The older (1979-1991) style Maglites were actually machined from 2" aluminum irrigation pipe and have a larger ID than new Maglites. In 1992 Maglite started extruding their own aluminum tube for machining that more closely matched the dimensions of a D cell battery. As such this heat sink is too small for most of the lights I'm looking at restoring. I wrapped it in thick aluminum foil tape for approximately 10 winds until it fit snugly into the ID of the light. The ring at the top is still larger so it still keeps it from being pushed into the light.
And here's a shot when it's all assembled. I used Arctic Alumina epoxy to affix the LED board to the heat sink. The driver snaps into place and all of the wiring is 22 gauge stranded. My soldering leaves something to be desired and I'm working on that. Any tips are greatly appreciated. I'm using 0.6mm solder.
Switch
You've probably noticed that the driver has two contacts, far different from the flange base of a PR incan bulb. The heat sink also fits snugly inside the barrel so the post needs to be removed from the stock Maglite switch. This is actually easier and a benefit of the older Maglites. The switch was cast in 2 parts so the post is easily removed. Newer (1992+) lights require sawing of the switch to remove the post. When removed a spare positive battery contact can be installed in place of the spring and straightened with pliers to to provide a space to hook up the positive driver lead. Sometimes the spot weld on the bulb spring contact can be broken and it can be straightened and used as well. The negative contact can be cut, shortened, and used to attach the negative lead from the driver.
I used spade connectors to connect the leads to the driver board from the switch. They need to be crushed down to fit the thin contacts but they make the switch much more serviceable later on. The negative spade connector doesn't need a shroud because the light is grounded to the body so it really can't produce a short unless it somehow contacts the positive connection. Alternatively the leads can be soldered to the contacts. My switch now works again!
The Light
As with most of my builds reflector and lens is key. I almost always opt for a KAI Domain MOP or OP reflector to really even out the beam and make it more floody and overall more useful. For this light however I re-used an older SMO KAI Domain reflector which has more throw. I also added a KAI Domain glass lens that allows for better light transmission, is more scratch resistant, and won't be affected by the heat on the high mode.
The total cost, excluding tools, on this build is as follows:
Adventure Sport
$17 - Heat Sink Pill
KAI Domain
$4 - 3500K Cree XP-L LED on 10 mm board
$6 - BD39 Driver
Total LED Drop in Cost $27
Optional
$10 KAI Reflector
$4 Lens
Obviously this isn't worth it from a financial standpoint because you can buy a brand new ML300L for around $40. Add in a couple hours of my time and the cost gets up there pretty quick but I do think they are very cool and make for a real tricked out one of a kind restomod Maglite. The first one of these I did went to a fellow who restored an old K5 Blazer and wanted a beat up old school 6D light to match the truck. If folks are willing to spend big on an old truck or car what's a few bucks for an old Maglite to go with it?!
And last but not least, please find a few beam shots with comparisons from a couple other lights below. The first 3 show the 3 modes, 5%, 30%, and 100%. The 30% and 100% modes are tough to differentiate because of the SMO reflector and its throw. At a distance, or with an MOP reflector, they are much easier to tell apart.
And shown below is this warm, 3000K, XP-G vs. a Cool ~5000K Malkoff. The 3000K XP-G looks like is has a much more yellow tint but the picture may not have come out correctly because it doesn't look that yellow in real life. It is more the color of the morning sun. The tighter hot spot of the SMO reflector on the Cree warm XP-G can also be seen vs. the greater throw of the OP reflector on the Malkoff.
Overall I'm very happy with the end product. I have to work on my soldering technique a little bit because it overall looks very sloppy. I'm always amazed at how clean the business end of a Malkoff looks. It's a work of art I have not yet mastered. For my first build I'm really happy and I learned a ton. I wrote this to help others understand the selection process for LEDs, drivers, etc and to provide a guide in case someone else wants to restomod a Mag. If anyone has any feedback (good or bad) I shoor wood appreciate it!
I should note that I will also put these lights together for anyone interested. I have a large stock of old, vintage Maglites and I can also modify any D cell donor Maglite. My contact info is at the right if you have any interest.
As always I'm looking to buy Vari-Beams and Vintage/Rare Mags. Please let me know if you have any, top dollar paid.
