Quick question re surefire drop ins

So I have a drop in on order, but I already have a ultrafire wf502b that I'm not so keen on and thought the led assembly would drop in my 6p, tried it, it worked, so took it out dog walking.

However it very quickly got very hot (body of the light) so I stopped, I think it was the batteries that were overheating CR123s, is it because this XML led was designed for 18650s or what? Why did the light heat up?

If you're running a light designed for 3.7-4.2v with 2xCR123s, you are going to be seriously overloading the driver. That's very bad. You're lucky it didn't on you.

Like I said I'm pretty new, why was it overloading the driver, what volts does 2x cr123 put out I thought they were less powerful than 18650s

Somnophore said:

Like I said I'm pretty new, why was it overloading the driver, what volts does 2x cr123 put out I thought they were less powerful than 18650s

Click to expand...

Because in series voltages are additive. That is, 2 x CR123A = 6.0 V, which is way more than a Li-Ions 4.2 V. I don't know the light specs, but spend more time reading here - you'll learn a lot, and it's important to know what a light can and cannot handle. Some lights will run direct drive because they only have a boost circuit and you can prematurely fry the LED with a li-ion - even though the light WILL work for a time. Others can handle it with a buck circuit. Like I said, there's a LOT of information to know.

Yes it's pretty new to me so a lot to learn, what's the difference between RCR123s and standard CR123s? I've seen some say they can't run on Rechargeable, and some run best on RCR123s, I just thought they were the same just one was rechargeable.

Somnophore said:

Yes it's pretty new to me so a lot to learn, what's the difference between RCR123s and standard CR123s? I've seen some say they can't run on Rechargeable, and some run best on RCR123s, I just thought they were the same just one was rechargeable.

Click to expand...

They are similar in physical size but different on the inside (have different chemistries). The RCR123's have the same chemistry as the 18650's and are rated at 3.7 volts each (4.2 when fully charged). Putting two of these in series when fully charged would give you 8.4 volts.

As mentioned above, the CR123's are 3.0 volts each or 6.0 volts when two of them are in series.

The right battery depends upon the light or more specifically its bulb (if incandescent) or its electronics. Some lights can handle primaries and rechargeables while others may only be designed for one or the other.

Ahh ok so yeah the rechargeables are higher voltages