Seeking recommendation for Li-Ions in Series

sween1911

Flashlight Enthusiast
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Dec 10, 2003
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Not sure if 21700 vs 26650 has been done already, but I'm putting together a sleeper Mag-mod for a friend with an Adventure Sport 5000-lumen Maglite head. Matt's builds usually have two 26650's. Illumn and Mtnelectronics are my go-to. I don't see KeepPower button-top 26650's in stock but there are flat-top 26650's and button-top 21700's. Not sure if the EWA (EVVA?) is of similar quality.

1) Can I use two flattop 26650's in series and have them make contact? Might be too close to call
2) Would two button-top 21700's give similar safe and reliable power? There's button-top 21700 KeepPower's also at 6000mah
3) Should I insist on finding button-top 26650's? Is there a decent brand of button-top 26650's?

Any overall tips for running these modules with respect to powering? Normally I'd recommend that yes there are plenty of better lights for the money, but a friend inherited a special Maglite and really wants to hook it up, so I'm taking care of him.
 
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I have Matt's rig. The flattop keeppower 26650s work fine in mine. (I have the 4200lm) The keeppower flattops stick out just enough. He did ship a small magnet just to be sure if I used different cells, but it wasn't needed.
Just be sure to get a high amp discharge cells.

This is all going to depend on what size mag your friend has and how you go about modding it that will dictate what batteries work.
 
Hey @bluflaam777 thanks for the info. I was just about to buy the 4200 lumen unit and suddenly everything went outta stock on the lumencraft site and their ebay portal. I picked up an original Adventure Sport 5000 lumen unit from a different distributor on ebay. So when you say "High Amp Discharge cells" is that the mah number or a different descriptor I should look for? I was just going to find the highest mah version I could.

Build notes: the Mag is a 4D incan D-serial number, so post-mid 90's. My plan is to use a piece of PVC pipe to center the cells in the body, and a piece of aluminum or copper rod as a spacer between the mag switch and the nose of the first battery. Some crimping of the stock spring so it hits the tail of the second battery and a wire bypass. I could pull it off with either 26650's or 21700's, I'll build around the battery size, that's no problem, I'll just get the correct size pipe.

I've made a couple Mag / LED / Li-ion conversions. I have a 3D with a Malkoff module and a single 26650 with spacer rod.
 
Sween, the amperage discharge rate is different than the mah storage numbers. Just for comparison,, you can look at keeppower's versions of their 26650 cells and you'll see different discharge rates even between their own cells. I also have xtar 26650 that are 10amp discharge and they work fine in my torches.
The 5000lm might have a higher draw tho? You can contact Matt/Mary via their site and I'm sure they'll tell you what their module draws and make batt suggestions.

Your build/mods sound awesome! Shouldn't have any issues.

My 5D mag was a gift from a friend/boss from 25yrs ago. Thought I'd lost it but found it in a tub in the loft.
But needed an LED upgrade. More sentimental value than anything. Except for me mucking with it (reversable) it looks brand new but now floods the whole backyard.

Just check his site for the 26650 he sells and notice the discharge rate. You can find those specific cells a buck or two cheaper around the net, but they don't always list the ratings or have outdated ones listed. I'd ask to be sure. I have the 10amp discharge keeppower, but he now sells the 12amp.
 
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1) Can I use two flattop 26650's in series and have them make contact? Might be too close to call
2) Would two button-top 21700's give similar safe and reliable power? There's button-top 21700 KeepPower's also at 6000mah
3) Should I insist on finding button-top 26650's? Is there a decent brand of button-top 26650's?

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I just bought some recently

May work Here



Battery.jpg


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They aren't needed with the keeppower or the xtar tho'. At least not in my mag, L6, L7 that all take 2x 26650 in series.
But I have seen some flattops that are truly flat and wouldn't work without a pill or magnet
 
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