Switch Maglite LEDs? XL50 to 3D

[Siggyhk]

I recently read that I could switch out the LEDs between a multi-mode 2xAA Maglite LED and a 3D Maglite LED. I have a couple 2xAA maglite LEDs, but would prefer to keep them stock.
I recently got a XL50 and it doesn't see much use so I'd like to switch it's LED with the current one in my 3D.
Can anyone tell me if it's possible for a novice to remove the LED from an XL50, and if so, can I expect it to turn my 3D into a multi-mode light? Also, will the XL50 work as a single mode light with the LED that's currently in my 3D?
Both of these LEDs are marked 091. -Thanks.

 

[Siggyhk]

Okay, I decided to jump into this myself without waiting for advice and it's not looking good so far.

I managed to get the 3D apart without too much trouble (it's not back together yet however). Then I tried knock out the LED in the XL50 by putting a pencil on it and tapping the pencil. This didn't work and everything seems pretty solid, so I'm thinking the LED may be be removable as with the other Maglites.

So, after failing to get the LED out of the XL50, I decided to go at one of my AAx2s. I used the pencil technique and the LED came out. However, the small clear dome directly over the LED fell off. Any advice on what to do about this would be appreciated. -I am in possession of the dome.

 

[Robin24k]

If it still works, your best bet would be to toss the dome. There's no way to fix it.

 

[PCC]

I hate to tell you this, but, the XL50's modes are changed at the tail cap. Changing the LED module won't change this.

 

[Robin24k]

That's true. Also, the 2AA LED module won't work in the 3D, it'll work with a 2D light though.

 

[Siggyhk]

I appreciate the replies. I did some searching and also concluded that I'm gonna have to just live without the dome. Unfortunately there is a significant decrease in output. It's also a darker beam now.

On the up side, I did get a LED from a 2xAA in my 3D and it does work. I have high, medium, strobe, and SOS. As far as I can tell up to this point, it has similar brightness on high as it did when stock. -Should I be concearned that this may not be as reliable a light as the stock 3D was? Also, this multi-mode LED is marked 080 or 030.

I saw the XL50s LED was marked 091, as was the stock 3D, so I thought they'd be perfect to switch. -It never occured to me that the tail-cap was what was actually changing the modes.

So, now I've got a multi-mode 3D, a domeless multi-mode 2AA, a single mode 2AA, and some slight knowledge/experience messing around with Maglites.

 

[Robin24k]

How bright is the 2AA module (090) in the 3D? Same as 2AA, or same as 3D?

I don't think the 090 is buck/boost, so it may be overdriving it (although alkaline voltage sag could end up only giving the LED ~3V, which is fine).

 

[Siggyhk]

The 3D seems to be the same brightness on high now as it was with the single mode module in it. The 2AA seems to be slightly brighter with the different module, but I couldn't say for sure.

I'm not sure about "buck/boost" or "voltage sag", but will try to educate myself. Anything you can tell me would be great. -Are you under the impression that I could potentially be doing harm to these light with these configurations?

 

[Robin24k]

White LEDs generally want to get a forward voltage of around 3.3-3.5V. Not enough voltage will result in decreased brightness, and too much voltage will overdrive the LED (or worse, burn out from thermal runaway). 2-cells are around 3.0V, so these lights use a boost circuit that increases voltage. 3-cells are around 4.5V, so these use a buck circuit to decrease voltage. Very few lights have both types of circuitry, so they need to be used with the intended battery source to prevent voltage issues.

When current is drawn from a battery, its voltage will drop from the open circuit voltage (1.5-1.6V for alkalines). Alkalines are notorious for significant voltage sag, especially under the high current draw of a flashlight. This reduces the voltage going to the LED, so the LED won't actually get 4.5V. I haven't made any measurements of an alkaline battery under load, but if they drop to ~1.0V each, you won't have a problem since the total voltage is less than 3.5V. This is probably what is happening in your case.

As evidenced with the 090 and 091, different LED modules are used for 2- and 3-cell lights. This leads me to believe that they are either buck or boost, but not both. Using a buck driver with lower voltages (3D module in 2AA) won't hurt, but using a boost driver with higher voltages (2AA module in 3D) will let the higher voltage go straight to the LED. If you use NiMH batteries or AA lithium primaries in an adapter, you may have a problem with the 2AA module running on three cells.