Rechargeable Surefire L4 2009

I have one of the new L4's (120 version) and I'm looking at a rechargeable setup for it. I've searched all over but there doesn't seem to be much info after the 2009 version was released.

According to MDs guide 2x3.7v might work ok but I don't want to wind up frying anything.
MDs Rechargeable Guide

What would the runtime be like with 2xIMR16340's or 2xLiFeP04's?

Get Aw's Protected 17670.
http://www.cpfmarketplace.com/mp/showthread.php?t=200812

Since the Seoul L4 is a single mode light, I think that you could use two CR123's. In any event it would not harm the LED to try it out, and the best way to do that is to take a current measurement at the tailcap with a DMM. Tailcap removed apply the red lead to the unadodized rim of the body and the black lead to the battery end, with the red DMM lead plugged into the 10 or 20 amp imput. If the current is significantly lower with two RCR123's (3.7-4.2 volts) than two CR123's it is ok to use the RCR123's.

Bill

I concur with Bullzeyebill's suggestion. You will see that the E2DL is listed right beside your new generation L4 as possibly compatible with 3.7v RCRs in Mdocod's guide. I've been running my E2DL on AW 3.7v RCR123s for more than a year now with no problems. It pulls .81 amps with fresh Surefire CR123s and .60 amps with freshly charged RCR123s. You should probably see similar RCR123 figures if the L4's regulation circuitry is compatible with the extra voltage.

I'm certainly interested in what you find, as I've been looking for someone to verify L4 compatibilty for a long time now.

Assuming the L4's current draw is close to that of my E2DL, I would estimate the runtimes as follows:
2 x AW 3.7v RCR123 750 mAH / 62 minutes
2 x AW 3.7v IMR123 550mAH / 47 minutes
2 x AW 3.0v LiFePO4 123 500mAH / 34 minutes

Presumably the new L4 uses a buck driver. So the question is if the driver can take the greater input voltage from 2x16340 vs 2x123A without frying the driver. Merely taking 1x17670 and 2x123A tail current measurements, for example, isn't going to answer that.

Telling someone to measure the tail current in their new L4 with 2x16340s as a method to determine whether or not this battery combo will work is putting the cart before the horse.

Yes, mdocod's guide hints that 2x16340 might work, but it hasn't been verified that the buck driver is actually rated to run safely at those input voltages.

It is helpful that 2x16340 seems to work in the E2DL, but unless you know that the E2DL and L4 use the same driver, you still can't be sure that Li-ions are safe to use in the L4. Further, if the E2DL's driver is rated to say 8V max, it may not be a good idea to push the driver at its limits anyway. Works in the short term vs works in the long term can be two different things.

Thanks for the input guys. I'll probably order some rechargeables and try it out, if it fries anything I'll just use it as an excuse to mod it.

Hopefully, SF hasn't threadlocked these new L4s as securely as their U2As. If the L4 is tightly threadlocked, opening the head might prove "fun".

Hi, i cant decide between the old 100 lumen and new 120 lumen, will the new one run on 1 x 17670, 1 x 16340, 1 x cr123 ? if i was going to mod to xpg or something later which model would be best since they are running different circuits ?

Assuming the old L4 uses a boost driver to run a Lux V, swapping in a low Vf XP-G probably isn't going to work out very well. For 1xLi-ion, your Vin is probably going to be greater than Vf, and the driver will be in direct drive for most of the run time of the Li-ion.

The old boost-driven L4 is probably a better match for a 2S2P MC-E. I need to test my old KL4 with MC-E mod on a bench power supply in terms of input voltage for running in regulation. However, I definitely get lots of lumens out using 1x17670. I measured about 630mA drive for one KL4 and 660mA for another. That's over 300mA drive per core for the MC-E, which translates to close to 400 emitter lumens for an M bin.

I assume that the new L4 uses a buck driver to run a Seoul P4. That is probably a better match for an XP-G, as long as the drive current in full regulation makes it worthwhile. I'd probably would want something around 700mA or 800mA min, or else the lumens increase would hardly be worth the effort.

I wouldn't bother with 1x123A. The input voltage is most likely going to be too low to run in full regulation, and you will probably get undesirably low drive current.

Whether the new L4 mod'ed with an XP-G is a good match for 1xLi-ion is a hard question to answer definitively. It depends on the drive current, the XP-G's Vf, the battery voltage sag under load, and the resultant driver input voltage needed for full regulation. And you aren't going to find that info anywhere, unless someone here on CPF has mod'ed a new L4 with an XP-G and has characterized the driver performance.

If you need 4.2V input to reach full regulation, then 1xLi-ion isn't going to run your light in full regulation for very long. If you need 3.9V, then you are getting somewhere. The challenge is finding the data to inform your decisionmaking.

Now if 2x123A is ok, then there is little question that an XP-G mod would run in full regulation.

I recently mod'ed a new version SF U2A (Seoul P4 LED) with an XP-G R4. The voltage to run in full regulation dropped from about 4.5V to 4.0V, making 1x17670 moderately reasonable. Drive current was about 915mA.

I'd love to run with 2xLi-ion but don't know if the driver can take the voltage and I don't want to risk frying it. I'm not going to find a multimode driver replacement on DX with Hall effect sensors.

great info thanks :thumbsup:

Anyone looking for an answer to the OP's original question feel free to look here.