Surefire M4-CB

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dradee1

Newly Enlightened
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Apr 2, 2007
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Does anyone know of any rechargeable setups that work in a Surefire M4-CB instead of the stock 4 Cr123a batts?

Why are these not recommended for use in Surefire flashlights?
http://batteryjunction.com/4parc390reli.html


Sorry if this has been discussed allready, I could not get the search to work properlly.

I love the M4 but hate its battery appetite..

Thanks
 
An easy setup for the M4 is to use two of AWs protected 17670 batteries and the MN16 lamp from the M3T (or the MN15 lamp if you want less light but longer run times) AWs cells are available here:

http://www.candlepowerforums.com/vb/showthread.php?t=140362

You DO NOT want to use 4x RCR123s in series. You are almost certainly going to kill one or more of the cells due to one being over discharged. Generally these smaller batteries are not good with higher current drawing lamps, especially the lamps in the M4. You could end up with one exploding inside the light in a worst case scenario.

So as I stated at the begining, get yourself a couple of AWs protected 17670 cells and use them instead to power an MN16. AW also sells a charger. I use this setup in a 9P with an A19 extender and a KT turbo head, which is a poor mans M4, works really well.
 
Thanks for the reply, I really dont want to change the lamps would these 17670 cells not work with the M4 lamps?
These 2 cells would just fit right in the place of 4 cr123`s?
How about the Protected 18650 cells he has?
 
The MN60 and MN61 lamps in the M4 will not work well on 8.4v-7.2v from the 2 x 17670s since these lamps are 12v lamps. The MN15/MN16 lamps are '9v' and run very well on the 8.4v-7.2v put out by the li-ion cells. The li-ions sag less under load so although at first glance you appear to be operating at a lower voltage than the MN15/16 is designed for, but you are not, since standard cr123s sag more.

A 17670 cell is twice the length of a cr123, so two of them fit the same as four cr123s.

18650 cells are too fat to fit in the M4. Some people bore out their M4s to fit the 18650 cells, but if you don't want to even consider changing lamps I'm assuming you wont want to bore out your M4 either.

If you really want to run 18650 cells, and they are the best thing for running an MN16, you can get a Leef body from Lighthound that takes two 18650s and fints the M4 head and tail cap.
 
Good info, but when I say I dont want to change the bulbs I mean that I want the same intensity that the M4 has stock but with rechargeable batteries.

The light throw of the stock M4 MN61 is awsome but like 10-20mins of runtime sucks on 4 CR123`s, I never have it on more than 30 seconds do you think that 4 rechargeable CR123`s could handle short bursts like that?

Maybe a new light body to hold 3 or 4 of those 17670 or 18650 cells would be nice.

Guess I`ll keep looking
 
I've learnt that you should never run batteries hot off the charger. Leave at least one hour. I used to use the above setup but I thought it was physically too long when compared with a 2 X 18650 tube that can produce 500 lumens with the MN21. I appreciate the 3 X 18650 with MN61 will give better runtime but I cannot quote the figures.
 
brunt_sp said:
I've learnt that you should never run batteries hot off the charger. Leave at least one hour. I used to use the above setup but I thought it was physically too long when compared with a 2 X 18650 tube that can produce 500 lumens with the MN21. I appreciate the 3 X 18650 with MN61 will give better runtime but I cannot quote the figures.
Click to expand...

Did you use the proteced 18650`s or unprotected? I guess if I try this I will just have to be carefull and check the voltages of each cell or maybe change to a MN21 bulb in the M4 head.
 
I would suggest the MN61 on a 3x18500 before I would suggest a MN21 on 2x18650.... the reason is that, the 3x18500 configuration will allow you to use protected cells, while the 2x18650>MN21 solution will not. 3x18500 body is only about 20mm longer than 2x18650..

from what I have read so far, the MN61 handles the overdrive reasonably well, but is driven VERY hard on this setup, using the 18500 cells INSTEAD of 18650 cells reduces the likelihood of instaflash. I estimate 20 minutes runtime with about 500 true torch lumens with a fantastic white color temp on fresh (but rested)cells.

The 2x18650 on the MN21 would be somewhere around 15 minutes runtime, and I estimate about 650 true torch lumens on this setup. This setup is, in my opinion, dangerous, the cells are being pushed very hard, I don't know of any 18650 cells that are speced for >5A drain rates.
 
Mdocod, where do you get a 3x18500 body that fits the surefire M4 head and tailcap?

Thanks
 
I'm not aware of anyone that sells a 3 X 18500. In effect that would be 4.5 X 123.
Another option would be to wait for Leef's C cell bodies to come out.
http://www.candlepowerforums.com/vb/showthread.php?t=158560
One of these 2 X C fitted with an M4 head and MN21 should be supersafe. According to Leef its total length will be 233 mm. This compares to 255mm for a Leef 2 X 18650 C-M with M4 head and SW02 tailcap.
 
interesting, I skimmed through the leefbody selection on lighthound too fast, never mind, you're right, leefbody doesn't make a 3x18500, I thought they did.

The 2xC body >MN21 looks like a great setup. Big scary cells, but at least they would be operated within reason.
 
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