SW02 tailcap dimmer than my Z48 & LOTC (New findings)

It's a very specific but minor problem I have regarding my SW02 and its use with a KL5 on a C3 body with 17670 li-ion and a dummy battery. It's minor but very irritating especially since the SW02 is not a cheap tailcap.

When I use both the the standard lock-out tailcap and the Z48, the KL5 seems to put out just a slight bit more light than when I use my SW02.

The SW02 and LOTC are some of my oldest tailcaps. Though only about 6 months old, they've been used heavily in many SureFire bodies. The Z48 is quite new. Measuring the resistance between the tailcap spring and contact 'tabs', the Z48 has a resistance of about 0.8 ohm while the SW02 has a resistance of 1.0 ohm. Could this 0.2 ohm difference really be responsible for the slight dimness?

I've also noticed that the KL5 is quite sensitive to the position of the dummy battery in the C3 body. If placed in front of the 17670, the KL5 will be more likely to flicker or dim-especially when the battery is starting to empty. Another resistance-related problem?

Re: SW02 tailcap dimmer than my Z48 & LOTC

RE: The flickering. I think in all the rechargeable-battery discussion and the various items needed to make them work, there has been mention of an additional spring needed to take up slack. You might want to look into that.

RE: The resistance. That's a bummer. I've heard from many, including Size15's, that the SW02 is the serious application tailcap to beat all tailcaps. I recommend a disassembly (as much as possible) and a liberal application of contact cleaner or alcohol. Perhaps going so far as to SLIGHTLY abrade or polish questionable contact surfaces to eliminate any dirt or oxidation that is giving you a problem.

Re: SW02 tailcap dimmer than my Z48 & LOTC

Thank you for the advice... I made quite sure the 17670 plus dummy battery were well-matched with the C3 body as far as length was concerned.

I've experimented with a few more configurations with and without the dummy battery in bodies of different lengths. In each time, I found the dummy battery to have some effect on the level of flickering. The flickering is not immediately noticable to the average person but it's there even if the flashlight is not in motion.

I'll try to clean my SWO2. It's never failed me before and rightly so since it's a weapon-light part (and not cheap!). I think I have to really tighten it down all the way to get the best performance possible. I don't have to do this with my new Z48 though.

All in all, I'm starting to build confidence with the idea that the KL5's boost circuit is very resistance-sensitive especially at lower battery voltages typical of a single 17670.

When I get my hands on a proper lightmeter, I hope to be able to measure more of these parameters.

Re: SW02 tailcap dimmer than my Z48 & LOTC

You may like to consider cleaning the contacts with some rubbing alcohol on a q-tip type thing.

Al

Re: SW02 tailcap dimmer than my Z48 & LOTC

Size15's said:

You may like to consider cleaning the contacts with some rubbing alcohol on a q-tip type thing.

Al

Click to expand...

+1 on what Al said, this will probably get rid of that .2 ohm resistance you are finding.

Re: SW02 tailcap dimmer than my Z48 & LOTC

Thanks guys!

At the moment, I'm trying to get hold of something that'll clean well without leaivng too many fibres behind.

An update on the SW02: Even when fully tightened, it's still causes the KL5 to be dimmer than the LOTC. When the battery is of higher voltage, this is much less noticable. Hopefully cleaning of the tailcap will solve this problem.

Re: SW02 tailcap dimmer than my Z48 & LOTC (Interesting outcome)

An update to anyone interested:

I've not yet cleaned my old, dirty and "higher resistance" SW02. Instead, I did some tests with a new SW02 I had lying around purchased at around the same time as the other SW02. Interestingly, both tailcaps have the same higher resistance readings when compared with my Z48 tailcap of which many of us suspect has the same internals.

Still, there was a high chance that my DMM and my simple resistance measurement techniques were at fault for the unusual readings so I did a run-time test.

For the test, I used the same flashlight setup (KL5+C3 body+17670+dummy battery), same li-ion battery (reading 4.17V open-circuit reading at start of test) and exact same duty cycles. The test was done in reasonably still air.

The result:

The Z48 ran the KL5 very slightly brighter than the SW02 but also hotter -too hot to hold in the tropical weather. As a result the KL5 lasted about 1h before rapid dimming affected its usefulness.

The SW02 (most likely as a result of its extra resistance and the sensitivity of the KL5's boost circuit) allowed the KL5 to run very slightly dimmer and cooler. It would get very warm but not too hot to hold. In the end, I had an extra 20 minutes of runtime before rapid dimming set in at the 1h 20m mark.

Therefore, it's very likely that my SW02 (perhaps NOS) is indeed different internally from the current Z48.

you know if you wanted to get rid of one of those ''bad'' sw02 i would trade for an surefire hurricane pack:naughty:

nice finding by the way does it affect incadecent lights or just leds?

Thanks for the offer but I think I'll keep the SW02 for a while longer! The resistance doesn't seem to affect incans. Also, when used with an MN16 run continuous for over 16 minutes, the tailcap doesn't get hot any faster than the rest of the flashlight.

The readings you get are pretty high even for the Z48. Let's say the KL5 pulls 1A. Voltage drop = 1A*Resistance=1V for the SWO2. Doesn't sound right. Did you "zero" your ohmmeter? That is, short across the lead and measure. You'll get a reading that is a measure of total resistance of the leads and all the electrical paths in question.

In any case, even if you get it rectified, I have found that the older SF clickies like the SW02 ALL have excessively high resistance. So your complaint is valid and I'm surprised no one else has noticed this. Even the non-lotc switches for the C/Z/M series (forget the model designation for those switches) have noticeably more resistance. The best test is to get a HOLA and test the switch in question with shorting across the (-) end of the cell to the light body. Use the shortest leads possible to minimize resistance. You'll see that the beam is yellower with the older switches. Please try this test and report what you find.

FWIW my older Gladius would flicker when fully dimmed. After light sanding on the end of the battery tube the effect disappeared. Are you CERTAIN there is not corrosion/tarnish where the tailcap meets the battery tube?

Paladin

Thanks for the tip CM,

Yep I admit my testing techniques are not very accurate. If I had the equipment, I'd use a larger contact area to do the measurement. My DMM and its testing leads add an additional 0.5 ohm. Still, there remains a minimum of a 0.2 ohm difference between the new(LOTC, Z48) and old (SW02) tailcaps.

I know a 1 ohm resistance is pretty high considering the current running through an MN15 or 16. That's a lot of wasted energy so I thought a runtime test with LEDs was the best way to confirm the extra resistance. Indeed, the SW02 does perform like a mild dimming switch which boosts useful runtime by a significant 20 minutes or 33%.

I'd like to do the test with incans that you mentioned but I don't trust the accuracy of my perception enough to get into that yet. I do plan on buying a light-meter to aid measurements but for the moment, I'm quite happy with overall performance of my incan setups.

In a few months, I plan to run an MN21 from 2x18650 li-ions in an M4-like body being produced by Leef. Anyway, during my research of such a setup, I came across some members running essentially the same setup in a bored-out M4 body. Some have noticed a lot of tailcap heat within a few minutes while some have no such problems. Also, one of the cases did specifically state the usage of an SW02.

Paladin, regarding the flickering (quite mild unless li-ion is at low voltage), I'm pretty sure it's not due to corrosion anywhere on the flashlight body/contact areas. It's more likely due to:

1) My usage of the old SW02 which I can safely say does add some resistance over newer tailcaps.
2) The use of a dummy battery does also add some resistance, hence contributing to flickering at lower voltages. A prior test with and without the dummy battery confirms this.

I have a Gladius too (my favourite LED!) and seeing how it works, the corrosion is understandable. With the Gladius, the end of the battery tube doesn't get anywhere as much rubbing and grinding (hence cleaning) by the tailcap contact as with SureFire's lights. My C3 body used with the SW02 is wiped and lubricated pretty often so I'm very sure this flickering is due to the sensitivity of the boost circuit and the extra resistances mentioned. Similarly, U2 owners also report some flickering when the light starts to lose power from the battery.