2 X 26650 in parallel for SST-50

I've done a Maglite mod, a 2D, using britelumens SST-50 D heat sink and a d2Flex driver. I'm using 2 X 26650's in a taped pack wired parallel. It works great as long as I don't use level 5 (max) with the pack fresh off the charger - after just 5 minutes or so on level 4 I can safely use any mode for the rest of the battery pack charge (otherwise I get a hint of blue on max.) I'm happy with this arrangement, although I will consider a high current buck driver in the future, in which case the 26650's will be in series.

I worry a little bit about the IMR 26650's, and would like to use a PCB for protection of the pack. I've got a couple of these:
http://www.batteryspace.com/pcbfor37vli-ionbattery85a-1alimit.aspx

Question: Should I use one module for the 2 batteries of the parallel pack, or 2 modules - each one protecting each battery, with the load / charge connections in parallel?

Or, just not worry about it? I measure ~4.8a on max at the tail with a fresh charge.

Thanks for your help.

John F

I personally dont think the IMR's need protection. I think you would be better off regulating current to the led with a board like you said. 5a is not a lot for those BS 26650's they are rated at 10a each.

Keep in mind that measuring the tail will give you a number but it will be less than what the led is actually seeing, so you may be well over 5a so that is maybe why you are seeing "blue"

Cool build BTW I bet its bright!

JohnF said:

I can safely use any mode for the rest of the battery pack charge

John F

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And how long is this for?

Also, I am kinda interested to see how you set up the battery pack. Post pics if you can. I am working on a 2 D right now and seriously considering those same batteries.

Keep moving along, nothing to see here but a ghetto parallel pack. 2 IMR 26650's with 22g wire soldered minus to minus, plus to plus, a couple layers of duct tape in between the batteries to insulate them, a wrap of duct tape holding them together, scrap sham-wow around the whole thing to give it the diameter of a D cell (no rattling) and a little electrical tape holding the 'spacer'. Pretty fancy, eh? For charging, just remove the pack and use magnets to hold the charger clips to the exposed pos and neg.

Tail cap with anodizing removed with dremel, spring cut in half to sit in the bottom, fits perfectly. All pretty ghetto, but it works, and is a wonderfully functional light.

I've not measure run time, but I walk one hour each night, I use it switching between level 3 (.8a), level 4 (2a) and level 5 (4.5a). It lasts 3 nights easily, then the pack usually measures around 3.6v, current draw and brightness have diminished a bit, and it gets charged.

I've gotten to love the d2Flex, I'm playing with one of the bike modes for walking, switching to the slow strobe mode to stay safe with the occasional car.

The momentary switch mod was the hardest part for me, but just followed the directions on one of the excellent threads on this topic.

It is easily my brightest flashlight (not counting HID) - I've intentionally sacrificed a bit of throw for a large spot and lots of spill by using a MOP aluminum reflector from britelumens. It still has terrific throw, though, and puts out a ton of light over a large area.

JohnF said:

Keep moving along, nothing to see here but a ghetto parallel pack.

Click to expand...

:laughing:

Well, no one can see it once inside the tube. :devil:

So, you will put these batteries in series if and/or when you get a cc driver.

420light said:

:laughing:

Well, no one can see it once inside the tube. :devil:

So, you will put these batteries in series if and/or when you get a cc driver.

Click to expand...

Hey! Are you mocking my elegantly designed and executed pack??? <g>

Yep, I'm looking at this as temporary (for now, anyway). With a buck driver I'll just pop the 26650's in regular serial. After seeing how little difference there is in light output between level 4 (~2a) and level 5 (~5a) on a fresh charge, I'm thinking more about putting in the HipCC that is just sitting in the original envelope here in my garage. I think I can live with a long-running 2.8a on max. If I do that, I'll probably just run the d2Flex in duomode bike mode to keep it really simple - a medium, a max, and a slow strobe if wanted.

JohnF said:

Hey! Are you mocking my elegantly designed and executed pack??? <g>

Click to expand...

No SIR.

Anyway, I just wish a dedicated CC driver for the SST-50 and SST-90 would be available soon.

420light said:

Anyway, I just wish a dedicated CC driver for the SST-50 and SST-90 would be available soon.

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Yep, I think I'll use the HipCC for another project (P7 mod for a friend's bike helmet light) and just leave the mag direct drive until a good single CC driver shows up for the SST's.

I bench tested an 'i' bin P7 (vf 3.25) and it seems very happy and very bright at 2.8a with the HipCC. I'll be using a flat series/parallel pack of 4 x 18650's for the power source, so another ghetto pack is in the works! Duct tape will probably find its way into this pack as well... I know you'll be interested in seeing pics. <g>

Yes, I think that you should save your HipCC for the P7, or perhaps even a MC-E.

Yes I will, I LOVE Pics. After all, forums are useless without pics.:nana:

Hey JohnF just wanted to say you might want to keep the ability of your SST-50 mod to be driven at 4-5 amps instead of setting it down to 2.8 amps. I say this because my SSC P7 2.8 amp mod is brighter than my SST-50 mods when I drive them at 2.8 amps. I guesstimate it takes about 3.5+ amps for a SST-50 to start walking away from a 2.8 amp SSC P7 output wise. I have sent one of my SST-50 emitters mounted on a good heatsink to another CPFer who will be doing tests to actually determine the nitty gritty. Happy Mods!

Fulgeo said:

Hey JohnF just wanted to say you might want to keep the ability of your SST-50 mod to be driven at 4-5 amps instead of setting it down to 2.8 amps. I say this because my SSC P7 2.8 amp mod is brighter than my SST-50 mods when I drive them at 2.8 amps. I guesstimate it takes about 3.5+ amps for a SST-50 to start walking away from a 2.8 amp SSC P7 output wise. I have sent one of my SST-50 emitters mounted on a good heatsink to another CPFer who will be doing tests to actually determine the nitty gritty. Happy Mods!

Click to expand...

I think you are right. Let me know how the tests turn out please.

John F