MadMax boards + input voltages

Hi, I've got some questions regarding the MadMax converters.

Based on what I've read, I understand that the MadMax would be able to properly regulate driving a P4 emitter (at 700mA for the Plus version) from 1.2V input. Is that correct?

If I was running a single battery setup with this board, could I potentially put a Li-Ion (3.7V nominal) cell in without damaging it? I believe that this would result in simply direct driving the LED through the circuit board, so I wouldn't be expecting any form of regulation, but I wouldn't want to fry the board.

Also, I'm a bit confused as to what is on the backside of this board. Does it has a standard positive battery contact pad and a negative/ground ring around the outside? This would be going into the pill in a Fenix flashlight head.

If it seems that I'm looking at the totally wrong driver, could you suggest something else? What I'm looking for is a driver that can run on 2*AA NiMH cells, while also being able to use a single battery tube for 1*AA NiMH or 1*3.7V Li-Ion. I'm looking for regulated current output of about 0.7A to the emitter. Thanks!

A li-ion battery and a Madmax would more than likely kill the Madmax board.

This was not true several years ago when the Vf of most LEDs were in the 3.2-3.6V range. The small drop across the converter when overdriven meant the DD current to the LED was not too excessive.

Todays LEDs are much lower in Vf and they are stiffer rising less with more LED current. This leads to a larger DD current than before and will exceed the Madmax safe operating levels.

Madmax doesn't regulate LED current and is considered a semi-regulated driver. It does regulate by limiting input current to 1A. With 2AA setup and todays LEDs it would be pushing close to 1A to the LED again due to the lower Vf than in the past. A single cell will still drive the LED and be in the 300-500mA range again depending on battery voltage and Vf of the LED.

Madmax only has the battery anode contact on the backside. The ground ring was introduced in later boards.

Wayne

Hi Wayne,

Thanks for the reply! The LED that I'm looking at using would be a neutral white SSC P4. Not one of the super recent high output LEDS, so the Vf should be in the 3.25-3.5 range.

Still, it sounds like the MadMax might not be the ideal converter for this application. In that case, I did also consider the GD buck/boost converter. Based on some of the formulas that I read, I believe I calculated that a single NiMH battery could still allow for 0.4-0.5mA through the emitter. It is also my understanding that 2 NiMH (2.4V) would allow for full regulation. Is this all correct?

Thanks again for taking the time to reply!

Only the Madmax will run below 1.6V or on a single cell. All the other converter boards stop working below 1.6-1.8V and won't run at all on a single AA cell.

The other boost type converter board would be a classic Zetex design. Both the Madmax and Zetex would behave similar.

Wayne

dat2zip said:

Only the Madmax will run below 1.6V or on a single cell. All the other converter boards stop working below 1.6-1.8V and won't run at all on a single AA cell.

The other boost type converter board would be a classic Zetex design. Both the Madmax and Zetex would behave similar.

Wayne

Click to expand...

Looks like I might end up getting MadMax Boards along with GD boards to play with at some point, I might be make more mods than planned so I'll wait and see on that. Thanks for the reply!

I do have another question at the moment though. If I wanted to make a sandwich using a MadMax board, what else would I need? If it matters, the host would almost certainly be a 2AA Mag. Is the mad max compatible with the same emitter board and connectors as some of the other boards? There wouldn't happen to be any current MadMax pictures, would there? I haven't seen any so far or I might be able to spare you some of these questions.

Not like a classic sandwich, but have you considered the OFC AA Mini Maglite heat sink from mariposaoyako? It is quite easy to build. Solder the leads to the driver board as usual. Put a solder blob on the anode pad for a hard contact point to the terminal of the top battery. Apply some Kapton tape to cover any potential component contacts to avoid shorting against the heat sink's driver cavity. Secure the ground wire and run the LED wire leads through the feed holes. Use some thermal glue to secure the driver against the sink. The copper heat sink is fairly substantial and also makes good contact with the Mini Mag body tube, which thus can assist in heat sinking.

Justin Case said:

Not like a classic sandwich, but have you considered the OFC AA Mini Maglite heat sink from mariposaoyako? It is quite easy to build. Solder the leads to the driver board as usual. Put a solder blob on the anode pad for a hard contact point to the terminal of the top battery. Apply some Kapton tape to cover any potential component contacts to avoid shorting against the heat sink's driver cavity. Secure the ground wire and run the LED wire leads through the feed holes. Use some thermal glue to secure the driver against the sink. The copper heat sink is fairly substantial and also makes good contact with the Mini Mag body tube, which thus can assist in heat sinking.

Click to expand...

Thanks, I've already got a couple of those for my personal mods. Really excited to put those together! However, I'm hoping to make some even cheaper mods for others who would like them, and it would be a major bonus if I have the option of retaining the twist switch function.

Ps: Any good places to order Kapton tape? I'm having a weird issue where my internet connection doesn't seem to want to use any google-based searching... I've got electrical tape, but the Kapton tape keeps popping up on here so I might as well try it out.

IIRC, I ordered 1/2"x36 yd Kapton tape from Amazon.

You can retain twist switch function using the mariposaoyako heat sink. Install the heat sink without the screw-on retaining collar. The heat sink body can move up and down, just like the original plastic holder for the bi-pin AA Mini Mag incandescent bulb. Or at least it can using the Fraen LP optic from The Shoppe, which pushes on the LED (I'm using a Seoul P4). Screw the head down all the way and the head/optic pushes the heat sink down and away from the battery tube lip, breaking the electrical circuit. Unscrew the head, the heat sink comes back up from the stock tailcap spring pressure, the circuit is completed, and the LED lights up.

Justin Case said:

IIRC, I ordered 1/2"x36 yd Kapton tape from Amazon.

You can retain twist switch function using the mariposaoyako heat sink. Install the heat sink without the screw-on retaining collar. The heat sink body can move up and down, just like the original plastic holder for the bi-pin AA Mini Mag incandescent bulb. Or at least it can using the Fraen LP optic from The Shoppe, which pushes on the LED (I'm using a Seoul P4). Screw the head down all the way and the head/optic pushes the heat sink down and away from the battery tube lip, breaking the electrical circuit. Unscrew the head, the heat sink comes back up from the stock tailcap spring pressure, the circuit is completed, and the LED lights up.

Click to expand...

Thanks for the reply!

Not using the retaining ring is such a simple and obvious solution, not to mention a totally reversible and swappable one... why don't I ever think of these things? :shrug:
Good thing there are much sharper people like you around to keep me sorted! Any decently fitting reflector should do the same as an optic, unless it needs to be spaced off the top of the LED package for focusing. So if I'm not doing an aspherical mod then it will probably be fine. Cheers!

To keep the heat sink from dropping out of the Mini Mag battery tube when you change batteries, you probably can slide a small o-ring over the threaded section of the heat sink. A 9mm ID o-ring should work. 10mm ID might be just slightly too loose. I used a 7mm ID o-ring that I had laying around. Works great. Had to work to stretch the o-ring over the LED dome without damaging it. That is probably the biggest risk with a smaller ID o-ring. A 9mm o-ring probably won't need a lot of stretching.

The DX SKU 14598 18mm x 12mm OP reflector also works. The flat bottom presses nicely on the Seoul P4 casing, allowing for head twist switching. Beam quality is also good. Hot spot is the same as with the Fraen optic -- about 2100 lux at 1 meter.

I haven't tried a McR18 Seoul. Should work though. Like with the DX14598, you need to use an o-ring to help center the reflector in the bezel since the 18mm top diameter of the reflector results in a gap otherwise.