Spark SL6-740NW Tailcap Not Working?

Hello,
I just received my "new" SL6-740NW light that I ordered a week or so ago. To my surprise, in the box was an a post it note with "RMA: 422939" written on it. Lo and behold, the rear tailcap does not work. I won't mention who I got it from, since I'll give them the benefit of the doubt that it was a mistake.

Anyway, is this a common issue with this light? Looking at how it is designed with the battery sleeve, I'm worried that it is pretty much par for the course. Given that Spark just came out with the SL6S-740NW for the same price, I'm wondering if they realized they had a bad design, and got rid of the tailcap to alleviate it.

Thanks,
Nathan

Maybe I will look like a PITA but I always request to the seller that test the lights before shipped, I dont know if their do it, but that make me some relax...

I hope that you resolve the problem soon...


SFMI4UT

You should be able to get another RMA number and return it for replacement. Annoying, isn't it?

NathanF said:

is this a common issue with this light? Looking at how it is designed with the battery sleeve, I'm worried that it is pretty much par for the course. Given that Spark just came out with the SL6S-740NW for the same price, I'm wondering if they realized they had a bad design, and got rid of the tailcap to alleviate it.

Click to expand...

Hi NathanF,

I had a same issue with very old version of SL6-740NW(i.e. can't turn the light on with a protected button-top 18650 cell which is a little long & thick because it's too tight in the aluminum sleeve).
But flat-top unprotected cell just works fine.

Now I'm using SLS6-740NW has neither tailcap switch nor sleeve. It works fine with not only unprotected 18650 but ptotected 18650.

Hope what I say is helpful to you.

candle lamp said:

Hi NathanF,

I had a same issue with very old version of SL6-740NW(i.e. can't turn the light on with a protected button-top 18650 cell which is a little long & thick because it's too tight in the aluminum sleeve).
But flat-top unprotected cell just works fine.

Now I'm using SLS6-740NW has neither tailcap switch nor sleeve. It works fine with not only unprotected 18650 but ptotected 18650.

Hope what I say is helpful to you.

Click to expand...

Thanks for the info and prompt response! I'm curious if I'm running into the same problem as you, or if mine is just defective. I'm using a 3100 protected Redilast that looks just like this one here: http://lygte-info.dk/review/batteries2012/RediLast 3100mAh (Black) UK.html

It is a tad bit tight going in, but nothing too bad. With the battery in, I used my multi-meter to ohm out the sleeve versus the outer body, and they do not appear to be shorted as if the battery is making the sleeve budge outwards.

In your opinion, what do you think of the design of the SL6? DO you think there is any credence to my (purely speculated) theory that it might have intrinsic problems, which is why Spark came out with the identically priced SL6S to replace it? I have to say, I rather like the idea of having the tail cap, but if there are issues, I'd just go with the SL6S instead. (It's an utterly supurb light apart from this one issue.)

You're welcome.
You have very nice 18650 batteries. I don't know the size difference between 3100 protected Redilast and my protected cell(JilLite & NLTEK brand, 2600mAh capacity).

I found my long & fat button-top 18650 is so tight that can't budge in the sleeve of SL6 and the sleeve end doesn't contact tailcap. So my gusee is the light can't turn on due to loose of contact of the sleeve end & tailcap. The sleeve is for tailcap use only as far as I know.

In my opinion, if you use a bit large protected cell, it's better for you to go with SLS6-740NW as I exchanged. :sweat:

candle lamp said:

You're welcome.
You have very nice 18650 batteries. I don't know the size difference between 3100 protected Redilast and my protected cell(JilLite & NLTEK brand, 2600mAh capacity).

I found my long & fat button-top 18650 is so tight that can't budge in the sleeve of SL6 and the sleeve end doesn't contact tailcap. So my gusee is the light can't turn on due to loose of contact of the sleeve end & tailcap. The sleeve is for tailcap use only as far as I know.

In my opinion, if you use a bit large protected cell, it's better for you to go with SLS6-740NW as I exchanged.

Click to expand...

Your assessment of the issues turned out to be dead on! (And you saved me the hassle from having to return this light.) Here's what I found with a bit of experimenting:

1) As stated by you and others, the sleeve's only purpose is to provide a path for tailcap operation.

2) Larger cells can chafe up against that sleeve. My Redilast 3100 mAh is one of these cells.

3) When the tail cap battery spring pushes the cell down, the sleeve also gets pushed down, causing it not to make contact with the tailcap. The issue is that the sleeve spring in the head is not strong enough to overcome the friction of the sleeve against the battery. I stretched the spring out a bit in order to help it provide some more force, but I don't know if that did anything or not.

The good news: It seems you can totally alleviate this problem with proper installation of the cell. To do this, you need to push the cell all the way into the light so it bottoms out. You then put the tailcap on without letting the cell pop outwards freely. Then, now that the sleeve is in line with the bottom of the cell, the head spring pushes the battery up, taking the sleeve along with it, and voila - contact is made, and the tailcap works!

I've tried this a number of times with both of my cells, and it's working 100 percent now. I also think it will eventually go away as an issue at all as the cells get smoother and thinner from being taken in and out.