Small handlight project

[gcbryan]

I got in an order today from DealExtreme. I ordered a dive light but while I was at it I ordered several cheaper lights ($15) to give to the kids of a friend for Christmas. While I was at it I ordered an extra either for myself or to use as parts if needed to make sure the two for presents worked correctly.

The cheaper light is the Romisen RC-K4. It runs on 3 AAA's, 1 18650 or two CR123's.

It seems to be well made. It has a clicky switch in the end cap or you can just click that on and then turn the light on or off by turning the end cap.

Except for the clicky end cap it would seem that this could be an inexpensive UW project and maybe it still can be.

I'm not sure what to do about the lens. I haven't been able to disassemble it yet (maybe not possible). If so why not use silicone caulk of some type on the edges and reflector side of the lens?

Use JB Weld on the threads for the head. I don't need to take the head off of this light anymore. Then the only issue is the tail cap.

It would be better to find a model just like this one with a solid tail cap but perhaps this one could be disabled and with JB Weld or something else in effect converted to a solid cap. That would still require an o-ring to seal the end cap where it screws on however for this basic project I would be willing to only screw the light on and off at the surface so perhaps just adding an o-ring without having a groove cut out would be enough.

I'm willing to risk a $15 flashlight but I would like some feedback as to whether this even makes sense.

I don't want a makeshift tacky project but if the end cap can be made solid from the inside and if the silicone on the lens works there is nothing tacky about it. Having to turn the light on or off at the surface isn't a problem for an experiment like this. I do this for most of my dives anyway as I need the light for the entire dive.

The light itself is only around 100 lumens. It's a nice compact size probably like the IST (just going by pictures).

Is there anything missing from my logic?

By the way the actual dive light that I ordered is the Cree MC-E dive light for $95 and it is almost as bright as my 10W HID Light Cannon. I just got it today and haven't had a chance to dive it yet. I went on a dive last night so it will be several days before I have another chance to do that.

It is well made. If it were $500 I'd want a few cosmetic changes but for $95...no problem!

 

[gcbryan]

Also, can anyone tell me if rechargeable 18650's need to be kept charged all the time to avoid killing them?

This aren't protected I don't think but my charger is smart enough to not overcharge them. As long as I don't run them down too long using the light what about when they are just sitting around?

My nicad battery pack needs to be changed every few weeks or once a month at least even when it's not being used.

I have two sets of these 18650's. If I'm not using one will I still have to keep them charged every month?

 

[gcbryan]

Is it possible to either order a solid tail cap for this flashlight or to find another small flashlight like this with a solid tail cap?

I've looked through the entire DealExtreme site in the category of DIY and for Romison flashlights and browsed as many of the other flashlights as I could and I can't find small lights with solid tailcaps. Does everyone has a clicky tail cap?

I do have a W200 on order as well but that turns on and off with the head which I'm not crazy about. It's also not immediately available now for some reason.

Any solution for a solid tail cap?

 

[gcbryan]

I'll get some feedback eventually.

So, so far I can't figure out how to disassemble the tail clicky switch (maybe it's not meant to be disassembled).

I also cannot see how to take the reflector out of the head so I can get to the lens to see if it needs reinforcing.

I can unscrew the head and I can unscrew the tail cap. That's it.

The reflector just turns around and around regardless of which direction I turn it but it doesn't unscrew from the lens and it doesn't just pull out.

Regarding the clicky assembly, I tried using some needle nose pliers to see if anything would unscrew. It looks like the silver disc with the spring coming through the middle would be threaded in there but I've had no luck.

 

[Packhorse]

A clicky switch will not work for a dive light.
A toggle switch is not only ugly but also likely to have its boot tear and leak.
A magnetic switch can be a little hard to implement on a small light.

A twisting switch is simple easy and effective.


My advice is if you want to mod a light for diving just start with a dive light. It will be better and cheaper.

 

[Dennis]

Also, can anyone tell me if rechargeable 18650's need to be kept charged all the time to avoid killing them?

This aren't protected I don't think but my charger is smart enough to not overcharge them. As long as I don't run them down too long using the light what about when they are just sitting around?

My nicad battery pack needs to be changed every few weeks or once a month at least even when it's not being used.

I have two sets of these 18650's. If I'm not using one will I still have to keep them charged every month?

Actually li-ion batteries hold their charge very well and will be almost 100% even after many weeks/months sitting around. Supposedly, looonnng term storage is best at cold temps and/or 40% of charge. If you are talking about the pointy ended DX Diving CREE light then the charger DOES terminate before the dreaded 4.2V. Just don't keep the cells on the charger much longer than necessary to be safe.

So basically, it is probably best NOT to keep charging them aside from a quick top off before you use them.

Dennis.

 

[gcbryan]

Actually li-ion batteries hold their charge very well and will be almost 100% even after many weeks/months sitting around. Supposedly, looonnng term storage is best at cold temps and/or 40% of charge. If you are talking about the pointy ended DX Diving CREE light then the charger DOES terminate before the dreaded 4.2V. Just don't keep the cells on the charger much longer than necessary to be safe.

So basically, it is probably best NOT to keep charging them aside from a quick top off before you use them.

Dennis.

Thanks. I rechecked my batteries and they do indicate that they are protected but I don't see a circuit on top of the batteries.

In any event I'll take your advice and I'll also just treat them as if they weren't protected.

 

[Dennis]

Thanks. I rechecked my batteries and they do indicate that they are protected but I don't see a circuit on top of the batteries.

In any event I'll take your advice and I'll also just treat them as if they weren't protected.

The protection circuit is usually on the bottom and it looks like it on mine. Regardless, my advice is the same for both types.

Enjoy!

Dennis.

 

[gcbryan]

I figured out how to take the reflector out. The head disassembles into two pieces. The lens is thin but may be ok for shallower dives. It is glass.

There is an o-ring in front of the lens, another one where the bezel screws into the head, a third one where the head screws into the body and a fourth one where the tail cap screws in.

I got the retaining ring unscrewed for the clicky switch. The switch was faulty. I removed the microswitch and used epoxy to glue the small pcb board with the spring attached to the back of the retaining ring. I connected a small wire from the spring to the outer rings of the pcb board which also make contacts with the retaining ring.

I'm waiting for that to dry now. Therefore I should be able to screw the retaining ring back in which will now include the spring assembly (we'll see if it holds).

This should convert the clicky to a twist switch. I'm going to invert the rubber end cap and use it as a plug from the outside and I'll then fill it up with either epoxy or silicone effectively (I hope) sealing the end cap.

I'll see if this make this light a small 100 lumen 60 fsw dive light for less than $20. This would be the equivalent of the UK SuperQ eled at $125.

Or it will leak.

At $17 it's a good learning/experimenting platform.

 

[Dennis]

I hope this works out for you! Good job regardless!

Dennis.

 

[gcbryan]

Well, I can at least report that this light has passed the 3 foot/3 minute test! I put it on a piece of cord and lowered it to the bottom of my 3 foot deep fish pond and left it there for 3 minutes.

I'll take it diving with me next time I go out.

 

[gcbryan]

Just as a follow up for anyone who has been following this project...I was eventually able to get a little water vapor behind the lens and this was in only 3 feet of water.

No other signs of water however. I decided to take the lens apart and to replace the o-ring with marine grade silicone sealant. I put some in the groove that was cut for the o-ring, some around the perimeter of the lens on both the inside (reflector side) and on the outside (in front of the lens).

I also used this on all threads in the head. The only threads I didn't touch are those for the tail cap since that has to be removed.

I'll take it diving with me just for grins next time I go. If the lens breaks then that will give me come useful info for the future. It it leaks and the lens doesn't break that will be useful as well. If I can take it to 60 fsw or so with no leaks that would be good news as well.

So far with my modifications the light looks essentially stock which is what I was most interested in.

Hanachan's posts were useful and informative but there is so much redundancy that it's hard to know what is useful and what is overkill or simply not effective. Therefore I decided to use this inexpensive but for the most part well made light to experiment with and to see what the actual failure modes are.

 

[gcbryan]

I went on a dive tonight and took this light along. I can report 100% success!

I was expecting failure but wanted to note depth and mode of failure. No failure. I turned the light on at the surface initially and just did a normal dive checking the light as I changed depth.

It never failed and I ended up going to 100 fsw. At that point I decided that the end to a perfect test was to turn the light off (worse condition) at 100 fsw (4 atmospheres). No problem.

This light is as close as you can get to still keeping the appearance of a stock light. It's a $20 light including batteries with less than $5 worth of epoxy and marine silicone sealant. It puts out 100 lumens in a light that is only 5" long and 1" in diameter. Machined aluminum, matte black, very nice looking.

The first picture is of the tail cap with a standard clicky.
http://gbpics.shutterfly.com/383

The next picture is of the modified tail cap (using epoxy and reversing the rubber end piece to use as a plug.
http://gbpics.shutterfly.com/385

The last picture is of the lens. It's hard to see but the perimeter of the lens has a little clear silicone showing.
http://gbpics.shutterfly.com/384

 

[gcbryan]

I think I've decided that silicone sealant is about the only option if you are going to try to convert a non-dive light to a dive light.

I located a better o-ring and put it in another similar light and I'm not even going to try to test it underwater. I can see that it's likely to fail

I'm sure using a better o-ring is the way to go if using a host that is already dive worthy but if something is not designed for diving simply putting in a thicker o-ring is not the answer.

In the case of this light I tried this but all that happened was that if you tighten the bezel a bit too much the o-ring extrudes through the bezel opening. If you back off you have no idea of how much to back off and now it's likely the light will leak for this reason.

 

[gcbryan]

Here is a picture of a hand free mount that I just made along with the light.

http://gbpics.shutterfly.com/387

I used a piece of PVC, mounted the light with 1/8" bungee and used 1/4" bungee for the hand loops. I cut down a section of pipe, used a quarter section, put it in the oven at 350 degree for a minute, flattened it out a bit and dropped it into cold water.

It keep enough of a curve to fit the back of your hand but is less curved than the original PVC. I threaded a small piece of scrap neoprene though the bungee used for the light to provide a bit of cushion.