Which bulb for Mag hotwire mod?

[Battery Guy]

Greetings Everyone,

I am planning a hotwire mod on a 2D Mag. The battery tube has been bored to hold one of Fivemega's 8AA-->2D battery holders. I am using PowerGenix NiZn AA cells. This gives an OCV of 14.4 V on a fully charged set of cells (1.8V each cell). My AA Ragone plot showing the performance of these cells compared to a few other popular AA batteries is here.

Here are the constant power discharge curves for the PowerGenix AA cells that I have measured (up to 16W):

I plan to use one of Kiu's high temperature bi-pin socket mods and a FM Throw Master head.

I would like to do something in the 75 W range (~10W per cell, ~10 minutes runtime). I have done a fair amount of reading, and have gone so far as to make my own spreadsheet with LuxLuthor's destructive testing. For this flashlight, I want a very white beam with a lot of throw. I have read too many threads where people have been disappointed in their hotwire mods, mostly because the beam was too yellow and/or the throw was terrible. I think with these PowerGenix cells I should be able to do something pretty impressive.

Given the discharge curves presented above, what would you recommend for a bulb in this setup?

Really looking forward to your input.

Cheers,
Battery Guy

 

[Battery Guy]

Actually, I am going to modify my original request slightly. There should be sufficient information in the discharge curves and the linked Ragone plot to give you a feel for how these PowerGenix AA cells perform. Based on the testing I have done to-date, these cells have the highest power capability of an AA cell (although, I have yet to test the Elite 1700 NiMH cells).

So, let's build ourselves a really awe inspiring light. Runtime be damned. I want something bright, white and a throw that is out of sight!

I already have the bored out 2D Maglite, the 8AA-->2D battery holder from FM, 8 AA PowerGenix cells, the Throw Master reflector assembly from FM, and the high temp bi-pin socket from Kiu.

So, how do I make this setup awe inspiring? Let's have some fun!

Cheers,
Battery Guy

 

[Databyter]

I'm gonna go out on a limb here and say Osram 64623 or similar.

With that head and those lumens it should have some throw and won't be yellow with those batts, although I hear some of the closeby bulbs might be even whiter, but your limited by voltage range somewhat.

I'm building something similar with 15.6V pack and a modified deep reflector to increase throw without adding diameter.

Someone posted a thread a while back that offered suggestions for a whiter solution for this voltage range, but personally I find the 623 bulb plenty bright and plenty white.

 

[Battery Guy]

I'm gonna go out on a limb here and say Osram 64623 or similar.

I was actually thinking about the Osram 64625, which is quite similar to the 64623. Other than the data shown by LuxLuthor's destructive testing, any idea what performance differences there might be between the two?

I think that with either the 64623 or 64625, the voltage of the pack will be quickly pulled down below 12V. Won't this substantially impact the "whiteness" of the light?

Thanks for your input!

Cheers,
Battery Guy

 

[Battery Guy]

... although I hear some of the closeby bulbs might be even whiter...

What are "closeby" bulbs?

 

[Justin Case]

It looks to me that you are in a no-man's land with your battery config. The cells themselves appear to have very high current capability. But you just don't have enough cells to deliver the voltage to sufficiently overdrive many of the super bulbs like the Osram 64623 and even the Hikari 5033. But you have too much voltage for the WA1185, WA1331, Hikari 5607and the like. The FM1909 looks to me to be your best bet, if the filament survives the initial in-rush. Unfortunately, it's an expensive bulb to experiment with if you are at an instaflash risk. A 64447 IRC would also work and there would be basically zero risk of instaflash.

I think if you really want a light saber, you need to go to 12AAs.

 

[Battery Guy]

It looks to me that you are in a no-man's land with your battery config.

Well that actually makes me feel a bit better. I have been going over and over the bulb charts and reading about other peoples mods, but just could not find the right bulb for this setup.

I think if you really want a light saber, you need to go to 12AAs.

That was the original plan, but FM is out of the 12AA-->3D battery holders, and does not know when he will be doing another build.

Cheers,
Battery Guy

 

[^^Nova^^]

Try mdocod for battery holders.

Cheers,
Nova

 

[Battery Guy]

Try mdocod for battery holders.

I did, but he won't make a 12 cell series holder.

 

[mrartillery]

I agree with Justin, thats kind of a odd voltage range, I would consider the 1909 with a soft start. Be bad to a $16 bulb!

 

[Battery Guy]

I agree with Justin, thats kind of a odd voltage range, I would consider the 1909 with a soft start. Be bad to a $16 bulb!

Not to hijack my own thread, but can you point me to some good soft start options? I had planned on getting a few of AWs incan driver modules, but he does not have any available. Any other good options?

 

[Justin Case]

You could use a NTC thermistor as a very simple, poor man's soft starter. CPFer Northern Lights has lots of posts on the subject. I do see two issues, however, with this approach:

- If the light will see cold temperatures (e.g., 0F-30F), the initial resistance of the thermistor may be quite high (on the order of 3-4 ohms) and the light is going to start out dim and possibly take a while to ramp up as the thermistor slowly heats up.

- The thermal time constant of the NTC thermistor may not be fast enough to support multiple soft starts in a row. How fast can the NTC thermistor cool back down to give you repeated soft starts? At some point, you won't need the soft start as the cells drain. But at the beginning with fresh cells and short bursts of light, you might need the soft start for multiple turn-ons.

Because of the first issue, I abandoned the NTC thermistor approach for a fixed voltage drop resistor in a Mag85 driven by 3xIMR26500.

 

[Battery Guy]

Thank you all for the fantastic information. It seems to me that I should hold off on my flashlight mod efforts until either FM's 12AA-->3D cell holders are ready (thus allowing me to overdrive some of the "super bulbs"), or AW's soft start incan drivers are ready (thus allowing me to run some of the high current, lower voltage bulbs without insta-flashing). In the mean time, I should work on reducing the tail spring resistance.

How's that for a summary?

Cheers,
Battery Guy

 

[^^Nova^^]

I did not read your post properly, I thought you were talking about 12AA>4D adapters, not quad bored 12AA>3D adapters. My bad.

Cheers,
Nova

 

[mrartillery]

As has been stated a NTC will work great, but AW's post said that his next round of drivers should be available within a couple of weeks, if you can wait that long.

 

[alpg88]

12v 50-75w mr16,
osram mr16 bulbs are brightest and have one of the best alignment\beam quality. and not expencive
no metal reflectors, no sockets,
you don't need soft stat with 14.4v,
i ran 50w with 4 32650's and 20w with 5 18650, and never flashed a single bulb.

 

[Battery Guy]

Thanks again to everyone for the advice.

I ended up making a decent (but far from impressive) light that should keep me satisfied until FM makes another run of 12AA-->3D holders and AW's incan driver switches are available again.

I replaced one of the 8 PowerGenix cells with a dummy cell. The pack now has a charged OCV of 12.8 V. I measured the 1k Hz impedance of the 7 cell pack and it was 0.13 ohms (compared to impedance of a single cell which was 0.014 ohms).

I paired this battery pack with a WA 1185 bulb. Although the flash voltage of this bulb is between 12.0 and 12.3 volts, it appears that the impedance of the battery pack (and perhaps the flashlight itself) is sufficient to bring the pack voltage down fast enough to prevent insta-flashing.

I used one of FM's bi-focal, cammed reflectors and bi-pin sockets, along with a borofloat glass lens.

I hate using a dummy cell, because I feel like I am just wasting space in the battery compartment. However, I just could not figure out how hit the sweet spot with respect to voltage and power.

That being said, I am quite please with the results. This is my first hot-wire mod, and the combination of FM's reflector and the overdriven 1185 bulb make a very nice 2D-size light.

I haven't made the measurements, but I suspect that I am running the bulb at darn near flash voltage, based on the battery pack impedance and the individual cell performance that I measured. According to LuxLuthor's destructive testing, 12V on this bulb draws 3.55A and has an estimated output of 1600 lumens. Based on the .13 ohm impedance on the battery pack, I expect an instantaneous 0.46V drop across the pack, which I think is keeping the bulb from going

I would love to get my hands on a few FM 1909 bulbs and an AW incan driver switch, which should allow me to use the battery pack with all 8 cells and double the lumens.

Thanks again for all of the input. Happy modding!

Cheers,
Battery Guy

 

[Quest4fire]

12v 50-75w mr16,
osram mr16 bulbs are brightest and have one of the best alignment\beam quality. and not expencive
no metal reflectors, no sockets,
you don't need soft stat with 14.4v,
i ran 50w with 4 32650's and 20w with 5 18650, and never flashed a single bulb.

Hi, alpg88. I've been lurking for a while, but the desire to mod something has finally prevailed. How do you go about connecting 5 X 18650 cells? Is there a battery adapter or did you make yor own? This sounds like a great 1st mag mod to try if I can get my hands on one of Kiu's high temp mag D sockets. Thanks for sharing this simple, low cost mag mod!

 

[alpg88]

Hi, alpg88. I've been lurking for a while, but the desire to mod something has finally prevailed. How do you go about connecting 5 X 18650 cells? Is there a battery adapter or did you make yor own? This sounds like a great 1st mag mod to try if I can get my hands on one of Kiu's high temp mag D sockets. Thanks for sharing this simple, low cost mag mod!

no holders, just 5d mad, paper rolled sleeve. 5 18650 cells loaded normaly in series.

my advice don't use 3,7v 18650 li co cells. use imr26500, or 26650. they can pull a lot more amps.
non imr 18650 is good for 20w bulb, may be 35w max, for anything bigger you need orange imr cells.

 

[Justin Case]

If the size doesn't dissuade you and if FM has another run of his 4.5" PAR36 head, a Mag mod using that giant head can be a tremendous thrower. Couple the head with a 13V GE4509, GEQ4509, or Martek 4509Q small plane landing light lamp. This does exceed your ~75W draw requirement. It looks like 8xPowerGenix may slightly underdrive a 4509. Perhaps a bored 3D Mag mod using 12xElite 1700s is better (if and when 12AA->3D holders become available).

Here are some example beam shots, comparing a GE4509 (4.5" PAR36 head) vs FM1909 (2.5" Throwmaster head) vs Osram 64440IRC (2.5" Throwmaster head).