Mag mod dilemma

A friend asked me to build a flashlight for him. I'm making a 3 x XPG @1000ma max per LED in a 2D maglight with multiple levels of brightness.

Here's the problem, I have a extra 2D-8AA batter carrier to keep the cost down. I want it so he can use regular alkaline batteries or rechargeables and 8 batteries instead of 6 for better runtime.

If he uses rechargeables, that's 11.2V off the charger. It won't be long before a buck circuit drops out of regulation. I want him to have decent sustained max brightness. Not just for 30 minutes before dropping brightness. Alkaline batteries can't sustain the load for long but make a nice emergency option.

A boost circuit will fry the LED's if he uses alkies or hot off the charger rechargeables.

Is there a nice buck/boost driver out there with variable brightness? I've looked but didn't see any.

Worst case scenario, I have to use a 2D-6AA setup (solder a wire into the 8AA battery carrier. I just prefer it if I can use 8AA.

Thanks,
Jeff

Boost driver TaskLED MaxFlex, you will need to mod the switch too use this driver......we can help you with that if you decide to use it.

Later
Kelly

So my first thought is: does the mag you have and plan to use fit the 8aa holder with rechargable batteries? I heard that only older mags would allow 4AAs to the D cell and that newer ones can't fit 4AAs in there since the tube has a smaller internal diamiter.
To be specific, my 2D mag will fit a pair of alkilines at 14.01mm with a pair of NiMH at 14.15mm, but not 4 NiMH at 14.15mm. (when I measure them I am taking the lowest reading, not where the plastic coating overlaps itself)

Do you plan to use high CRI LEDs? You are looking at about 10 watts with those 3 XP-Gs, thats similar to one XM-L and a similar amount of light output. So is there a reason you plan 3 LEDs instead of one? I'm not saying the XM-L is better I am just wondering if theres a reason for the XP-Gs.

If you were to use 1 XM-L and (rechargable) 6AA (in 2p3s) things look pretty easy with an 8x7135 driver. (alkilines shoudl work, mostly, but you waste some power as heat witht their higher voltage. and you might have less runtime if they sag sooner)

Sway said:

Boost driver TaskLED MaxFlex, you will need to mod the switch too use this driver......we can help you with that if you decide to use it.

Later
Kelly

Click to expand...

My output voltage at 1000ma is 9.9V. With the MaxFlex, it would direct drive it with 8AA until the voltage dropped or sagged below 9.9V. Rechargeables hot off a charger at 11.2V would deliver 3.733V per LED. Alkys even more. Wouldn't that fry the LED's?

yazovyet said:

So my first thought is: does the mag you have and plan to use fit the 8aa holder with rechargable batteries? I heard that only older mags would allow 4AAs to the D cell and that newer ones can't fit 4AAs in there since the tube has a smaller internal diamiter.
To be specific, my 2D mag will fit a pair of alkilines at 14.01mm with a pair of NiMH at 14.15mm, but not 4 NiMH at 14.15mm. (when I measure them I am taking the lowest reading, not where the plastic coating overlaps itself)

Do you plan to use high CRI LEDs? You are looking at about 10 watts with those 3 XP-Gs, thats similar to one XM-L and a similar amount of light output. So is there a reason you plan 3 LEDs instead of one? I'm not saying the XM-L is better I am just wondering if theres a reason for the XP-Gs.

If you were to use 1 XM-L and (rechargable) 6AA (in 2p3s) things look pretty easy with an 8x7135 driver. (alkilines shoudl work, mostly, but you waste some power as heat witht their higher voltage. and you might have less runtime if they sag sooner)

Click to expand...

I'll know if the 8AA holder will fit when the light arrives in a couple of days. I ordered a midnight blue maglite from actionlights. If it doesn't fit, I believe someone here can bore the light out a little. I'm using a triple xpg setup because my friend wanted a light that was obviously custom. The fact that I'm making it and it having a unique look is important to him. If that wasn't the case, I would have pointed him to a Fenix TK45 or something like that. If I don't use cool white then just outdoor white (R4) will be the other option. Color rendition not as important to him as output and impressiveness (but practical).

Jeff

HI xpit,

There are a number of simple solutions. The simplest being rather than wire the LEDs in series wire them in parallel. This way just about any buck converter will do. If you wired them in 3P you could use this driver. That would give 3 modes and you could use any 8AA cells.

If you wanted higher end parts 3A shark buck with remora would work with 3 parallel LEDs. Or H6flex in the same way if you want one of the worlds coolest UIs.

xpitxbullx said:

My output voltage at 1000ma is 9.9V. With the MaxFlex, it would direct drive it with 8AA until the voltage dropped or sagged below 9.9V. Rechargeables hot off a charger at 11.2V would deliver 3.733V per LED. Alkys even more. Wouldn't that fry the LED's?



I'll know if the 8AA holder will fit when the light arrives in a couple of days. I ordered a midnight blue maglite from actionlights. If it doesn't fit, I believe someone here can bore the light out a little. I'm using a triple xpg setup because my friend wanted a light that was obviously custom. The fact that I'm making it and it having a unique look is important to him. If that wasn't the case, I would have pointed him to a Fenix TK45 or something like that. If I don't use cool white then just outdoor white (R4) will be the other option. Color rendition not as important to him as output and impressiveness (but practical).

Jeff

Click to expand...

Another problem with a MaxFlex besides possible damage to the LED's using 8*AA's is the dimming function doesn't work with too much voltage. A MaxFlex would definitely work better with 6*AA's. Is your extra 8*AA battery holder from the Sandwich Shoppe? I believe their holders make the battery diameter the limiting factor as far as fit goes. Still NiMH batteries might not fit in the newer Mag-D's with 'D' in the serial number as yazovyet pointed out. Here is a thread where the author suggests 4*NiMH will fit in a newer Mag D as long as you take care to properly orient the battery sleeve overlap. If it came down to boring, wouldn't it be cheaper to buy a new 6*AA battery holder and save the extra 8*AA you already have for some other project?

Maybe you could use Download's Poorman Mutli-LED Setup with a 1,050ma or 1,400ma AMC7135 linear regulator. At 1 amp according the Silverfox battery shootout either Alkaline or NiMH batteries put out initially about 1.4 volts. The Cree XP-G data sheet at 1 amp has the LED Vf at about ≈3.375 volts or 6.75 volts for the 2 slaves. Leaving 4.45 volts for the AMC7135 if you use 8*AA's. The 7135 chips are rated for up to 6 volts but even 4.45 volts would require the chips to be Arctic Alumina epoxied to your LED's heatsink. That's doable if you're careful to solder the wires flat onto the board. The SnowplowTortoise heatsink is another good option for a regulator heatsink.

Parallel instead of series. How could I not think of that. Problem solved! The H6Flex has the perfect UI that I was looking for.

My 8AA holder is from the sandwich shoppe. I hope Enloops fit in the maglite.

Thanks for solving my problem. The answer was so simple, I couldn't see it. Haha

Your ideas were good, also, Al. Thanks for the input. I'm opting for the H6Flex because I was looking for the UIF setup.

Jeff