Rechargeables in Surefires

I've searched a bit and found a smattering of references about using rechargeable batteries in Surefires, but no overall, definitive answer.
So I'd like to bring it altogether in this one thread.

Here's the premise: Surefire lights are great (yea, yea, yea.. we get that), but the company has designed most of their lights to work with CR123's exclusively which can be a bit expensive for those who use a light on a daily basis.
If I didn't know any better, Surefire counts on making at least as much money on their battery sales as they do on the lights.

So is there a general rule about using 18650's (or whatever rechargeable) in Surefires?

You can use rechargeables in standard Incandescent lights if you use lamp assemblies from Lumens Factory or Ultrafire Lamps. They have lamps for the output of one or multiple cell rechargeable lights.

Ultralast and Ultrafire make 3.0 volt limited cells that use an internal circuit to regulate the voltage at 3 volts. They are a little on the chubby size and may not fit in all lights due to the overwrap of the shrink wrap to cover the circuit.

You can use an 17650 in a 6 volt light but it will be dim. Same with an 18650 if it fits. A little better to use two cells with a 9 volt lamp but still dim.

On SF LED products I have no practical knowledge. I have played lamp lego with them only.

Yea, it's mainly the Incans that came up when I searched, so I should have been more specific in my first post because it's the use of rechargeables in the Surefire LED lights that I'm most interested in.

Good info on the Incans, though.

9V LAs / bulbs designed for 3x CR123A primaries which draw no more than 2A will work well on 2x 17500 Li-Ions, which will fit into the same space.

The drawback with SF tubes is their 17mm internal diameter, which means larger-capacity 18xxx Li-Ion cells will not fit.

The smaller tube diameter would definitely make a difference...

What I was hoping, specifically, that I could use a rechargeable of some kind with both an L1 (single CR123 size), and the 2 x CR123 models, Kroma and P6.

I wonder if there might be a cottage industry waiting for someone to make custom tubes for Surefires that would accept the larger diameter batteries as long as the electronics of those lights would allow good performance from rechargeables?
I mean, hell, you can buy just about everything else for flashlights here from CPF members, including things I never thought anyone would want or need.

Zenster said:

I mean, hell, you can buy just about everything else for flashlights here from CPF members, including things I never thought anyone would want or need.

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Yep, including a screendoor for a submarine and a solar-powered flashlight.

Zenster said:

The smaller tube diameter would definitely make a difference...

What I was hoping, specifically, that I could use a rechargeable of some kind with both an L1 (single CR123 size), and the 2 x CR123 models, Kroma and P6.

I wonder if there might be a cottage industry waiting for someone to make custom tubes for Surefires that would accept the larger diameter batteries as long as the electronics of those lights would allow good performance from rechargeables?
I mean, hell, you can buy just about everything else for flashlights here from CPF members, including things I never thought anyone would want or need.

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I have been using the Tenergy RCR123 (the 900 mAh...not the LiFePOs) in a Surefire L2 Lumamax. At first I thought it was a no go because the protected cells were too fat. Then I said what the hell and I pushed one in, and another. The batteries worked well electrically but getting them out was difficult. When I got them out the outer wrapper was damaged. So I removed the blue Tenergy skin off and the battery had another thin clear skin holding the Kapton tape with the wire in place that connects to the microcircuit voltage regulator at one end. I then began using that stripped pair just for the Surefire L2 and I don't regret it at all. The runtime on high is about 20 mins, longer if intermittent. It is my most used light...probably 3 to 4 times a week for about 10 minutes each time when I take the garbage out at night (garbage collectors come by really early here and I'm too lazy to get up in pre-dawn hours) plus I use it when I run late mowing and weeding the lawn. It gets dark early and I always start late on yard work so I squeeze an extra few minutes of yard after sunset and I use the Surefire to get my mower and equipment put away in the tool shed. That light, lights up the entire shed like a car headlight.

I know that many have recommended against protected cells in a series, but mine work just fine and I top off the pair after every use or at least every second or third use. Those two cells travel together to the charger and back to the light together so they have "learned" to work in pair. Normally protected batteries have hiccups when used in a pair series because all that needs to happen to shut down is for one to dip below the correct voltage because they may have slightly different charges. Keeping them absolutely together for the charge and discharge overcomes any cell differences. I would not have it any other way. Before I got the rechargeable RCR123 I rarely used the Surefire because I just hated the idea of burning up $4 worth of batteries. The guilt was too great. Besides I hate primaries because you really want fresh batteries in a flashlight and the moment you start using the primaries they are anything but fresh. With the RCR123 you always have the choice of topping them off, and with 500 charge cycles I can enjoy those for at least two years. Anyhow, I rarely ever need to run it more than 20 minutes since the Lumamax gets so hot.


I keep the primaries for real emergencies and since they have 10+ year shelf life, it would be insane to burn them up in everyday use.

I have a SF L1 and L2 and a half dozen of the Tenergy 3.0 v RCR123's. I've been using them in my 6P and 9P with the DX 6090 LED drop-ins 3 to 18 volts, with good results. However, I've been hesitant to try them in my L1 or L2. Now I'll try the L2 with them but what do you think about the L1? I've got a meter and those Tenergy 3.0's meter at 3.8 to 4.2 volts out of the charger. Kind of makes me nervous with my all around favorite L1!

The definitive answer is YES!!! YOU CAN!!

But how you go about doing it is a long story. There are a lot of ways, but only some of the ways are really ideal.

Few ground rules: avoid the use of "3.0V" rated li-ion cells for use with incandescent configurations, they won't work correctly.

stick to quality brand protected li-ion cells. Or, if you must go with a "3.0V" for a bizarre application I suggest a LiFeP04 cell to maximize safety.

Which light are you planning on converting? There is a viable configuration with many lamp options for almost every surefire incan made, click on the link in my signature to see a complete list of configuration options and more details on using these configurations.

mdocod said:

Which light are you planning on converting? There is a viable configuration with many lamp options for almost every surefire incan made, click on the link in my signature to see a complete list of configuration options and more details on using these configurations.

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At the moment, I'm thinking of the L1, E1L, and later, a Kroma.
Naturally, these are all LED lights.

It's not just that I'd like to use rechargeables in them, but also try not to have to sacrafice much in runtimes while doing so (if even possible).
I don't yet have any Surefire Incans showing up on the horizon yet, but I don't rule them out for later.

Spence said:

I have a SF L1 and L2 and a half dozen of the Tenergy 3.0 v RCR123's. I've been using them in my 6P and 9P with the DX 6090 LED drop-ins 3 to 18 volts, with good results. However, I've been hesitant to try them in my L1 or L2. Now I'll try the L2 with them but what do you think about the L1? I've got a meter and those Tenergy 3.0's meter at 3.8 to 4.2 volts out of the charger. Kind of makes me nervous with my all around favorite L1!

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I use only "protected" cells from Tenergy, and other than the wrapper causing a tight fit, electrically they work well. There is a voltage protection circuit on the battery. Even though you can measure 3.7 volts (4.2 right off the charger) with a meter on an open circuit, the circuit does not allow current to flow out above 3.2 volts. The circuit works instantly to regulate output voltage at 3.0, then shuts abruptly off at 2.7v (if I remember correctly). The microcircuit protection protects the cell from 3 things. 1) Overcharging - cutting off current from the charger when the correct level is reached, 2) voltage regulation, preventing more than 3.0 volts from being delivered to the device when there is a load, 3) Low voltage cut-off, current is shut off coming out of the battery if the voltage drops below 2.7 volts to prevent over-discharging the cell and ruining it.

Its well worth it. Before I started using the rechargeables, the Surefire L2 was more of a conversation piece sitting on a shelf. I hated burning up one time use primary batteries. Once I started using the rechargeables, it saw regular use and gets topped off every few days.

Make sure that they are protected cells. You can take a power resistor like a 3 watt 100 ohm and shunt the cell and take a meter reading and see if the voltage drops to 3.0 volts to verify that the cell protection works.

The microcircuit protection protects the cell from 3 things. 1) Overcharging - cutting off current from the charger when the correct level is reached

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Lithium Ion cells need to be terminated at 4.10-4.20V to maximize cycle life and maintain safety, most protection circuits don't protect AT 4.20V, they don't kick in until closer to 4.30V. Which is too high for most applications. Don't depend on the protection to terminate a charge unless you know for sure what type of circuit you have.

3) Low voltage cut-off, current is shut off coming out of the battery if the voltage drops below 2.7 volts to prevent over-discharging the cell and ruining it.

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a Li-ion cell is basically dead at 3.5V, running it down to 2.7V frequently would be hard on the cell. Again, the protection circuit really is only doing the bare minimum to prevent catastrophe or reduce the likelihood of it.

Make sure that they are protected cells. You can take a power resistor like a 3 watt 100 ohm and shunt the cell and take a meter reading and see if the voltage drops to 3.0 volts to verify that the cell protection works.

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That will verify that the regulation works, but won't necessarily confirm that the protection functions are working. Not all protected cells are regulated.

mdocod said:

Lithium Ion cells need to be terminated at 4.10-4.20V to maximize cycle life and maintain safety, most protection circuits don't protect AT 4.20V, they don't kick in until closer to 4.30V. Which is too high for most applications. Don't depend on the protection to terminate a charge unless you know for sure what type of circuit you have.



a Li-ion cell is basically dead at 3.5V, running it down to 2.7V frequently would be hard on the cell. Again, the protection circuit really is only doing the bare minimum to prevent catastrophe or reduce the likelihood of it.



That will verify that the regulation works, but won't necessarily confirm that the protection functions are working. Not all protected cells are regulated.

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The specific cells that I am using and find very satisfactory are these found at ALL-Battery (Tenergy's Online store). I purchased the kit with four cells and bought an additional 10. I am using all of them and with the exception of the Tenergy Brand wrapper skin causing a tight fit in my Surefire L2, the cells have performed exceptionally well, including in my Fenix T1, Fenix P2D, and Fenix P3D rebel, and P1D CE. The voltages I posted are more or less what they spec on their web page and more or less what I have measured with my Fluke Multimeter.

As far as regulation, I don't believe the cells actually offer regulation but rather "cut-off voltage, and voltage-limited current draw. The only ill effect of the protection circuit that I noticed on the Rebel P3D is that when operated in the max brightess mode prolonged, it shuts down abruptly after 15-20 minutes without the early warning "strobe" produced when using a primary Lithium cell. This is presumably because the cut-off voltage in one of the cells, triggers before the Fenix circuit engages its low voltage warning circuit.

Below is what Tenergy Claims:

• Rechargeable CR123A Li-Ion Batteries with 3.0V working voltage and 900mAh capacity.
• Fully protected against over-charge, over-discharge, over-current and short-circuit.
• Tenergy RCR123A can be recharged up to 1000 times. 1 RCR123A Li-ion = 1000 CR123A Primary Cells
• Replace the most of CR123A primary Lithium battery for a digital cameras and flashlight
• Modified Voltage to achieve 3.2v at full voltage; once loaded, cell voltage drops to 3.0v.
• Internal over-charge and over-discharge protection to prevent battery over use. The current will be shut off when the battery voltage drops below 2.5V.
• Internal Voltage Regulators.
• Dimension: 16 D x 34 H mm. (The height 34mm includes the button top).
• Weight: 17 g or 0.6 Oz.

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I was purely pointing out that there are misconceptions about what these cells are, what voltage ranges are ideal, etc etc... Reading specifications only tells part of the story. My only point is to increase awareness of the way li-ion should be treated to maximize user safety and cycle life. Protection circuits are USUALLY set up at the maximum bounds of cell safety and shouldn't be bumped up against frequently. It prevents catastrophic overcharges or over-discharges, but doesn't provide healthy cell cycling if used as a stop point for charging and discharging.

mdocod said:

I was purely pointing out that there are misconceptions about what these cells are, what voltage ranges are ideal, etc etc... Reading specifications only tells part of the story. My only point is to increase awareness of the way li-ion should be treated to maximize user safety and cycle life. Protection circuits are USUALLY set up at the maximum bounds of cell safety and shouldn't be bumped up against frequently. It prevents catastrophic overcharges or over-discharges, but doesn't provide healthy cell cycling if used as a stop point for charging and discharging.

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You are probably right and I did appreciate the information which sort of made me double check the specs.

Thanks.

Spence said:

I have a SF L1 and L2 and a half dozen of the Tenergy 3.0 v RCR123's. I've been using them in my 6P and 9P with the DX 6090 LED drop-ins 3 to 18 volts, with good results. However, I've been hesitant to try them in my L1 or L2. Now I'll try the L2 with them but what do you think about the L1? I've got a meter and those Tenergy 3.0's meter at 3.8 to 4.2 volts out of the charger. Kind of makes me nervous with my all around favorite L1!

Click to expand...

I've been using the Tenergy 3.0v cells exclusively in my L1 for the past 2 months with no problems. They act like a primary cell, with less runtime. I use the light daily at work, and rotate the cells at least once a week.