MR11 maglite?

[Buck91]

Well with this bike light I've been toying with I've come up with the 'bright' idea of modding a maglite with a 15w spot beam (12* maybe) 6 volt MR11. I figure a 2-C or D cell with li-ion rechargables would give me 6-7 volts and some type of capacity capable of using the light -some-.

My question is two fold: How would I go about obtaining and/or making a fixture for the MR11 base inside the mag while still using the stock switch? And would li-ions give me the discharge capacity to run a 15w bulb without destroying my runtime?

 

[mdocod]

actually, MR16s are the much more popular lamp to use in mags because they are almost exactly the same diameter as the stock reflector, they drop in and fit nicely in most cases... all you need is a way to run the BI-Pin base...

There are simple drop-in PR-bi-pin adapters available, but as I understand it, they are for G4 pin spacing... you would probably need a KIU socket... (Which as I understand replaces most or all of the mag switch and tower assembly). The KIU supports a wide variety of bi-pin widths.

 

[Buck91]

OK, so MR16 seems the way to go for a magmod. Now, I have no experience with (r)CR123's, but I was thinking 4 of them into a 2C or 3C (whichever would have better fit!) into a 12V 15W (for 15/12 or 1.25A).

I'm thinking this type of setup for ease of use (don't have to deal with a dozen NiMH batts) and possibly somewhat longer shelf life?

I've heard things about RCR123's not supporting >1A well, and also about them being dangerous to use/recharge? Does this setup sound safe? Does it sound feasible?

Or maybe pair up 14500 lithium rechargables (those are AA size, right?) in two parallel D-adapters in series. Might get better runtime, I dunno.

 

[LEDcandle]

yeah, you need a kiu socket, and that requires some DIY and soldering work :-
http://www.candlepowerforums.com/vb/showthread.php?t=171607

I run a 3D MR16 mag using a 3D12AA battery adapter to power 12v MR16 bulbs, ranging from 20w to 50w. Runtime is only 25-45mins though.

Li-ons could work, but you'd need to be sure of the measurements and whether they will fit into your host of choice, what voltage you need and what the current is gonna be like. Try to stick to about 1.5C max of a li-on's capacity. And the figure written on the wrapper isn't always the truth.

So for 14500 and R123as, I'd think 1A would be about the most you should be pushing it.

Whatever the case, runtime won't be great if you want the light to be small. You might consider going for multi-LED or HID for a bike light.

 

[Buck91]

Nah, I got my bike covered (9Ah lead acid -> 6v 15w halogen and my MTE 1-AA rebel). I was just thinking this could be a fun little project to play with (slowly...slowly...) during the boring winter.

The only reason I don't like the idea of using a bunch of NiMH AA batts is recharging sounds like a PITA with that many cells. A simple 3v or 3.7v li-ion 4-cell would be around 12v and a 12w bulb with a nice tight beam would be pretty slick, I think...

 

[mdocod]

The only reason I don't like the idea of using a bunch of NiMH AA batts is recharging sounds like a PITA with that many cells.

The idea with these setups is not to try to charge the cells individually, but to pack charge the whole thing at once.. Pack chargers are around $20-100+ depending on how fancy you want to go... I use an intellipeak RC pulse charger (supports 4-8 cells, has variable current)... Think I payed like $50 for it many years ago at a hobby store in town.

 

[LEDcandle]

R123as are labelled around 600-800mah, but they have been found to be on the lower end of that range, especially at high currents. Pushing 1.5A might be risky if the true capacity of the batt is 500ma.

I use a 50w 10º Osram MR16 which pulls about 4.5A off my 12xAA NiMh (2100mah) (3D Mag), so I get roughly 20mins of dimming runtime. Yes, the beam is pretty slick and far reaching, and very 'flashlight-like' even though these lights are supposed to be fixture lighting because of the narrow angle.

I did another 150w 21v MR16 (4.5D mag) and transplanted the bulb into a 10º reflector; very nice, very bright, throws a lot of light far, but super hot and impractical to run for more than 1-2 mins, and it pulls 7.5A from my poor Sanyo 2500s.

And as mdocd says, you can pack charge the NiMhs just like a li-on pack.
http://candlepowerforums.com/vb/showthread.php?t=89363
http://www.candlepowerforums.com/vb/showthread.php?t=138652&highlight=clamp

 

[gswitter]

fivemega sells a G5.3 (MR16) bi-pin adapter as well.

I spent a few evening experimenting with various MR16 lamps and C Li-ions, and the combo does make for great, small flood lights.