Help with M6

[ebow86]

Yes, but when I decided to run it in my M6, I used two CR123's and a spacer. If you do a continuity check between the connections on the MB20, you can arrange them right, and get 6 volts out of it. I explain it in my M6/N1 thread...the best I could explain it, anyways.

Gotcha, sound's like an awesome setup, those N series LA produce such beautiful round hotspots.

 

[jamesmtl514]

Just got in, here are some photos for your consideration.
M91W with 2x 18490 vs. M6 with MN21
M91W is about an inch from the white molding. The MN21 is about 3 inches away. you can see the tip of it at the bottom of the photo.

C2 with extender and KT 3x 16340 with MN60 in vs. M6 with MN21. M91W with 2x 18490 on the floor.
Both incas are about 4 feet from the wall.

Reversed this time.
MN21 on left, MN60 on right. Pointed at the ceiling. about 8 ft away.(~9 ft ceiling, 12" light)

 

[DM51]

james, the MN21 pulls about 5.0 amps out of 3s2p CR123A primaries. It works them about as hard as they can take, so it is essential to use top-quality cells.

The voltage under that load drops to around 7.0-7.5V, so I'm a bit puzzled by your reference in post #13 above, where you measured 4.4V. How did you measure that?

 

[jamesmtl514]

I have only used Surefire batteries.
I achieved the 4.4v by running wires from the MB20 to the MN21 forgoing the M6 body.
I placed my multimeter leads on the outer and inner springs while the light was lit. It gave me 4.4.

**************************

If anyone here can post beamshots of their MN60 and MN21 side by side like I have that would be greatly appreciated.

 

[DM51]

At 4.4V the MN21 will definitely under-perform, with the result you've seen. Either the cells are old or used, or the MB20 has a bad connection that bypasses one of the cells.

 

[jamesmtl514]

I tried 2 sets of new cells. I'm leaning towards a bad MB20 at this point. How would I go about testing it?
(I will attempt AOW's N1 vs P60 method when I get my multimeter later on this evening)

 

[angelofwar]

I'm with DM51 on this one...Bad MB20...I'm Sure SF will swap it out for ya.

At 8' the MN21 should appear a little brighter than the MN60...and "white" for that matter.

Here's a quick diagram I did up showing how your MB20 should be wired to make up the two parallel 9V stacks.

 

[DM51]

I'm not sure exactly how the MB20 is wired up. Just looking at it would suggest it is 2s3p, but it's 3s2p. What order the wiring goes inside, I'm not sure.

I may be wrong, but I think someone has taken one apart before - probably LuxLuthor. I think I recall seeing something about it a long while ago.

Try various combinations of just 3 cells to get a reading of 9V at the +ve and -ve terminals of the MB20, then take those out and put 3 cells in the other 3 spaces. If there is a faulty connection, a reading of 0.0V will reveal it.

 

[DM51]

BTW in post #28, take those readings open circuit, without a bulb connected...

 

[angelofwar]

Ha-Ha! just did that diagram up while you were typing yours, DM!

Try various combinations of just 3 cells to get a reading of 9V at the +ve and -ve terminals of the MB20, then take those out and put 3 cells in the other 3 spaces. If there is a faulty connection, a reading of 0.0V will reveal it.

If you do this, just make sure you do it in a timely fashion. There's a "loop" in the circuitry...if you just put 3 in, or 4, etc., and they're not right (say you put batteries in A1, A2, and B2), and you accidentally leave them in there, they can get extremley hot (and probably go poof on ya)...it's either 3 in the right spot (A1, A2, A3), all, or none.

 

[Justin Case]

I'm not quite clear how inserting the wrong combination of cells can result in a "loop" in the circuitry, i.e., a short. The cells are wired 3S2P. Unless you connect the MB20 + to the -, how do you short the cells?

Also, I'm not clear on your battery topology. I put a meter to the MB20 to test continuity for all of the connections. I get the following:

    MB20+
      |
   --------
  |        |
--^--    --^--
|   |    |   |
|   |    |   |
|   |    |   |
----     ----
  |        |
--^--    --^--    These two pairs of cells are lined up on either side of the + sign on the top of the MB20.
|   |    |   |
|   |    |   |
|   |    |   |
----     ----
   |______|
      |
  |--------|
--^--    --^--
|   |    |   |
|   |    |   |    These two cells are the two on top of each other, lined up under the www.surefire.com writing.
|   |    |   |
 ----    ----
   |______|
       |
     MB20-

 

[jamesmtl514]

I just performed the 3 battery test on the MB20.
With all 6 batteries I get a reading of 9.1 (i've used the cells for my tests in this thread)
With the 2 on top 1 on bot I get 8.8v
With 1 on top 2 on bot I get 8.8v.

I bought 3 new MN21 bulbs. Maybe It's the bulb at this point...

 

[DM51]

Intriguing problem... very helpful input from AOW and others above... it will be fascinating to know what caused it.

If the new bulbs don't work any better, you should give SureFire a call and send it back - they'll definitely fix it / replace it under their lifetime no-quibble warranty.

 

[Justin Case]

I just performed the 3 battery test on the MB20.
With all 6 batteries I get a reading of 9.1 (i've used the cells for my tests in this thread)
With the 2 on top 1 on bot I get 8.8v
With 1 on top 2 on bot I get 8.8v.

I bought 3 new MN21 bulbs. Maybe It's the bulb at this point...

If you look at the MB20 topology shown in my post #31, there are four ways to obtain 9V nominal using three cells. It's possible that the two 3-cell configurations that you tested both tested only the left side of the topology I drew (for example). If the other parallel path wasn't tested and is defective, that would explain why the cells sag so badly under load. Your MB20 gives you essentially 3S1P instead of 3S2P.

Do you have a dummy cell to use in your M4 to test the MN21?

 

[jamesmtl514]

I do have a dummy cell. Good idea.

I just tried the MN21 in my M4 with the dummy cell. The light output was the same as when it was in my M6.
MN60 off 3 16340 was still much brighter.

 

[Justin Case]

The M4 test is a 3S1P test. If it produced the same output as with your M6, I would suspect a faulty MB20, especially since you measured 4.4V under load in your M6. An MN21 draws almost 5A in an SF M6. SF123 cells probably can hold 2.0V-2.2V at a 2.5A draw. So at 5A, I can believe that the cells might sag to 1.5V each. If the MB20 were working properly and giving you a true 3S2P configuration and assuming identical banks of 3S cells as an approximation, then each bank of 3S cells should see about 2.5A draw and the total voltage under load should be closer to 6.0V-6.6V.

I would re-test the MB20 to make sure that you check both banks of 3S cells.

 

[DM51]

Excellent thinking, Justin

 

[HotWire]

Please let us know what you found out! We are all interested in your success with the M6. Right now I'm guessing you have a bad MB20.

 

[JNewell]

Interesting thread. I don't recall many reports of MB-20s failing.

 

[Kif]

Wow, a faulty MB20!?
It's time to take out all my MB20s and make sure they are good :duh2: