Halcyon Scout / UK SL4 voltage questions...

[Scubaroo]

We've probably all heard that the reason that the Halcyon Scout (3 x C cell) design uses the Underwater Kinetics SL4 (4 x C cell) lamp, is that it's to prevent "overdriving" the bulb with a higher voltage than the lamp is rated, ie with alkalines, the Scout has a 4.5V source versus the 6V of the SL4, and therefore, the bulb in the Scout is less likely to fail when needed. Sounds like a fair argument.

But is the SL4 bulb genuinely being overdriven in the SL4? I've heard (but can't verify) that it is actually a 6V lamp, and thus would be matched to the voltage source, and not overdriven at all.

I note that on the UK website, that there is an industrial light they manufacture, called the UK300, which, in effect, is a non-scuba version of the SL4, but in a 3 cell design. Same form factor as a Scout light, and it shares the same rubber bezel as the SL4 (the part numbers match), but just uses a different (presumably lower voltage) lamp/reflector assembly, which should fit the Scout light (based on the bezel it sits inside of being the same one). I guess the question is then, is the UK300 lamp being overdriven? If not, what reason is there that the Scout couldn't be retrofitted with the UK300 lamp/reflector assembly, thus matching the lamp to the batteries? Would a 4.5V lamp be brighter than a 6V lamp, if they were both powered by 4.5V? Is the overdriven argument out of date?

Probably should be asking these questions of UW Kinetics....

 

[DNAXdiver]

No according to the airspeed divelite book there's no right voltage for a bulb but a tradeoff how bright do you want it to be and how long do you want it to last. Hotter burning filiment will put out more light for the electricity consumed but not last as long. Colder burning will waste electricity but last a long time. Overdriving a relative term - if you apply 6V to a 4.5V bulb 2000 hour bulb so it only lasts 100 hours you are overdriving it. If the manufacture rates decides to call it a 6V 100 hour bulb then its not overdriven its a high output bulb.

Can't compare light from a 4.5 and 6 without knowing amperage or wattage but given the same power consumed the 4.5 bulb on 6V should be much brighter than a 6 burning the same amount because it is trading off life for brightness.

Scubaroo once bubbled...
Would a 4.5V lamp be brighter than a 6V lamp, if they were both powered by 4.5V? Is the overdriven argument out of date?

Probably should be asking these questions of UW Kinetics....

 

[leadweight]

As the owner of an SL4, I must say that it is not all that bright on 6v (unless my light is brain damaged) and the filament throws all kinds of shadows. With one less battery it must be dismal.

For whatever it is worth, most 4.5v 3 c cell lights have bulbs in the 3 to 3.5 watt range. The Pelican Super Saberlight is one such example. It has a very narrow beam that drops off without much secondary halo. I mention this light because it turns on by twisting the light head and may be rigged and stowed DIR style. It is popular with cave divers since it can be bought for about $21. I have one, but it is not my favorite light. I do use it as a backup on night dives. Next stop could be my toolbox.

 

[Northeastwrecks]

Leadweight, you might want to check that bulb.

I have two Scouts (big surprise, right). They are rather bright for small lights. I use them on night dives and practice in wrecks (simulated can light failure).

 

[Scubaroo]

Now you two play nice in my thread, okay?

I have two Canadian Extreme (neo-Scouts), and they have a very focused beam, but I wonder if it could be brighter with the UK -300 lamp. The SL4 I found has a very similar beam, just brighter.

 

[leadweight]

Well, I did say my SL4 may be brain damaged. The bulb could be going bad. I have seen some big time unit to unit variation in other light heads. My last Super Saberlight threw a completely different beam than the one I have now. To bad it is at the bottom of the Coral Sea. There is also the possibility of some resistance in the switch. It once got completely messed up.

These days I use an Ikelite PCa as a primary for warm water night dives. It is really bright for a small light, but not so big as to scare the fish off. Definitely not DIR, but I actually saw a cave guide in Akumal with two of these on his BP harness with the bolt snaps and inner tubes. May not be the best choice as a backup light as the bulb is driven hard and battery life is short.

 

[Northeastwrecks]

I was being nice. He said that his light might have a problem.

Can you put either a Scout or another SL4 side by side in a dark room for a test?

Any chance that the reflector is dirty or damaged?

What shape is the lens in?

 

[leadweight]

I took out the batteries on the SL4 and they tested at 1.4 v. Bulb was sllightly off center in the reflector, so I gently bent it back. This produced some improvement. What I am mainly noticing is this light is putting out a warmer color temperature than I remember it in the past.

Initially I thought the batteries were OK, but a fresh set cleared up everything. This leads me to believe that alkaline batteries producing nearly full voltage can have greatly decreased current if old.

 

[lanun]

ok - this is the resut of the subjective test.

'appears' that the sl4 throws a brighter light than the scout.

i think the test is not as valid since can't vouch that both batteries and bulbs are equivalent (how long they've been used, etc). oh well.

maybe something more scientific is in order with control subjects, etc.

 

[leadweight]

On the UK website it says an SL4 at 6v is 5.5 watts. The 300 at 4.5 v is 3.1 watts.

One would think that an SL4 bulb in a Scout at 4.5 v would produce 4.1 watts ( 3/4 of 5.5). Is that right, or am I missing something? Any EE types listening?