Bullyson
Enlightened
Are there rechargeable batteries that will work in this light?
SureFire M6LT
- Thread starter Bullyson
- Start date
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I'm running 2 18650 Li ion cells in mine. No problems so far.
Bullyson
Enlightened
And how do you fit them in there? I didn't think 18650's would fit seeing the battery carrier for the 123's is longer than the 18650's.
Solscud007
Flashlight Enthusiast
You need to look into rechargeable M6 in the Incan section. You need a custom carrier or get a M4 devastated bored out.
A member on CPF Custom & Modified Flashlight with the name of mdocod sells the 2X18650 battery holder for the M6. The batteries are in series, side by side.
Bullyson
Enlightened
Thanks guys. What kind of runtime would two 18650's give? With six 123's it's running on 18v and I assumed it wouldn't run on two 18650's but it seems I was wrong.
The six 123's are 2 stacks of 3 cells. 9 volts with twice the capacity. Two 18650's are 8.4 volts with close to the same amp-hrs. I'm using 3100 mah cells.
angelofwar
Flashlight Enthusiast
My take is, it's an LED...why worry?
Bullyson
Enlightened
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Bullyson
Enlightened
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Bullyson
Enlightened
Going Gear was out of stock so I opted for Battery Junction and when I paid for the light I got an email saying they were back ordered and would be getting more the middle of March. I cancelled that order and found them in stock at Bright Guy. I got the light plus 2 day UPS Air for $315. Now my question is what are my options as far as customizing this light?? Is there a way to diffuse the beam without buying the FM24 since it's hard to find? Maybe a film?
Bullyson
Enlightened
Two 18650's are 7.4 volts correct? So you're saying two CR123's stacked are still 3 volts and not 6 volts?
Well the term 'stacked' is just a loose figure of speech. We're really talking about series vs parallel connected batteries. Let's say we're using CR123 batteries of 900mAh and 3.0v (nominal voltage) each:
Two connected in series will give us 6.0v and 900mAh capacity at that voltage or three in series will give us 9.0v and 900mAh capacity at that voltage. Conversely;
Two connected in parallel will give us 3.0v and 1800mAh capacity at that voltage and three in parallel will give us 3.0v and 2700mAh capacity at the stated voltage.
The M6 uses 6 batteries divided into two sets. Each set consists of 3 batteries connected in series (9.0v, 900mAh). Those two sets as a whole are connected in parallel or "3s2p" as what many here like to call it and that therefore gives us the total of 9.0v and 1800mAh capacity at that voltage.
From that point onwards, things get tricky as you may have read about how batteries 'sag' their voltage under load and then there's also voltage 'drop'. Voltage 'sag' at startup isn't that much of a concern for most LED lights nowadays. Rather, voltage 'drop' as the batteries deplete is more of a concern. Lithium primaries generally start at around 3.2v and will drop to below 2.8v by the time they're empty. Li-ions have a nominal voltage of 3.7v or 3.6v but fresh from the charger, they're usually around 4.2 to 4.1v each and will drop to below 3.6 or 3.5v when they're close to being empty.
Voltage 'sag' (for LED lights) starts to be important towards the end of a battery's life. A lithium primary that reads 2.8v when taken out of the light for measurement can be well below that once back into a flashlight and subjected to a load. So voltage 'sag' and voltage 'drop' will have to be taken into account to determine how to substitute lithium primaries for lithium-ions.
So if we do the math, an M6 starts out at around 9.6v when full and around 7 or something volts when empty. If you take into account voltage sag, then the batteries may be as low as 6 volts when nearing the end of their life. The heavier the load, the more the batteries will sag their voltage. Two li-ions in series will start at around 8.4v when full and will also drop to around 7 or something volts when empty and once again with voltage sag, may be as low as 6 volts or even lower if the load is heavy.
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I'd just like to state that voltage sag also happens at the start and remains throughout the run actually (again the serverity of sag depends on how heavy the load is) but voltage sag at startup is really more important for incandescents that are direct driven rather than many of today's LEDs which has a circuit to handle over or under voltages. However, even the circuit itself has its voltage limits. I'm not sure what voltages the M6LT will accept however. As long as we stick to within the range used by the lithium primaries, then we'll be safe. It may well be a wider range than that.
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HotWire
Flashlight Enthusiast
- Joined
- Mar 9, 2011
- Messages
- 1,651
I'm told that the Invictus has the same LED as the M6LT. I'm running the Invictus on 2 AW 17500 cells. It's very bright. Throws well with little side spill. I've not tested the run time, but it lasts a long time on the two AW 17500 cells. Of course I keep other batteries charged, and primaries for emergencies.
Bullyson
Enlightened
According to the Surefire specs the M6LT is brighter than the Invictus. The invictus is rated at 30,500 Candela vs the M6LT at 34,500 Candela. When watching the Going Gear comparison on YouTube there is a noticeable difference in the two lights.
theamazingrando
Newly Enlightened
- Joined
- Oct 31, 2005
- Messages
- 184
I don't have an Invictus for comparison, but my M6LT seems to have a slightly softer beam with more fill light than the UB3T beamshots I've seem. The optical window has a visible diffusion film on it that I have never noticed (nor looked for) when handling the Invictus. I love the M6LT beam! It's very focused, but has a nice Surefire-style "Fade" around the edges. It is, truly, the first LED I've had that in the same league as my M6/MN21. Running the two side-by-side is a great demonstration of how Surefire handled lumens ratings for their (constantly dimming) incans vs. their (regulated) LEDs. The "900 Lumen" M6LT is, indeed brighter than the "500 Lumen" M6--but you have to do a ceiling bounce and really look to discern it. After a few minutes of runtime, the difference is a little more noticeable. After 20 minutes it's even more visible! 
theamazingrando
Newly Enlightened
- Joined
- Oct 31, 2005
- Messages
- 184
Now that the M6LT is in a few more CPFer's hands, I'd love to see someone do a runtime chart for it! I want to know if it is set up for "max power" drive like the Invictus, or if they've managed a little flatter regulation for the single-level light with a 3s2p battery.
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Bullyson
Enlightened
I'm ordering two battery adapters for my M6LT and already have Callie's Kustoms 18650's but would like to know if the IMR's have an advantage over the ones I have now??
angelofwar
Flashlight Enthusiast
If it helps, the KX9 was designed as a replacement head for all the M-Series lights (minus the M2). I saw a dealers hand-out, and the KX9 was listed an an LED head for the M4...I E-Maile SF asking them if this was indeed correct, and they said yes. So, AFAIK, it good for 12 volts.
