Using a cheap Chinese bike light as a canister light head?

[DIWdiver]

Reasonable size, yes. But how are you going to hold it? You can't put a Goodman handle on it, it's got no good way for you to hold and control it in one hand, and it doesn't look that comfortable to hold in the hand.

Maybe you could modify the fin area to allow a Goodman handle to attach. Then it might make a decent head.

 

[lucca brassi]

You can made Goodman handle in that way that magnet in ring is build-in on the bottom of light holder ( maybe could work - but I think that can cable with it's torsion made problems )

Also you can remove contol ring ( do you need sos modes...? ) , shortcut inside hall switch or reed switch and use ring seat as solid base for Goodman handle and add switch on tank

I think that there is also version without ribs ( might causes problems )

http://www.ebay.de/itm/CREE-XML-XM-...06&rk=1&rkt=8&sd=170924196153&#ht_7037wt_1161

 

[demonic69]

You could fashion a goodman handle to slot into the fins easily enough, would also provide a bit of stability. As Lucca says, you could also use the magnet ring.
The switch isn't a problem as I'm designing a new switch that doesn't rely on the housing

 

[johnohuk]

Couple of tie wraps through the fins on the head will secure it fine, with a something to angle it straight...

I've noticed the rotating ring is the weak point, of the three I have, the ring is becoming loose OR getting stiffer on all of them, which i suspect is the spring and ball bearing rusting? Anyway, I think this the first bit that will fail..done about 18 dives (sea) so far with them...

How were u going to switch it demonic69?

 

[lucca brassi]

http://www.springandballplungers.com/-c-50_130.html

 

[demonic69]

An Inline switch Johno, using a reed switch and a ring magnet

 

[McGlencoe]

But with a 3200mha battery they last quite a while... not measured it yet but easily 2-3 days diving if not longer..

I get 2 dives with the stock 5000mAh battery and then the light really starts losing performance.

 

[McGlencoe]

I get 2 dives with the stock 5000mAh battery and then the light really starts losing performance.

I take that back, did a single dive tonight, got out to 89' and then slowly headed back in, by the 30 minute mark, my light was starting to flicker a bit dim and then go back to bright, the sign that the battery is starting to die off, it did last the entire dive, but not at it's brightest.

 

[johnohuk]

Hi McGlencoe,

what sort of battery were you using ? brand? capacity each?

From your last post i thought it was down to your batteries not delivering anything like 5000ma for them to last so short a time... But it made me go back and reevaluate what i'm using...

To add a little science to it I've made myself a very simple Torch Burn Time logger, now I've not tried it with the dive torch yet ( I need to work on the cooling!) but using a similar specified torch (2.2A at tail) I can record a 50-55min run time off a single battery using both my battery types (Trustfire from Dealextreme 2500ma and an Xtar 2600ma from Amazon.).

So i'm thinking, are your batteries really delivering the capacity they claim?

But like you, I noticed, that one of my three has started to flicker slightly, it doesn't show up on the video ( 25fps) so i don't care too much but not sure what is causing it yet... I replaced the battery and it made no change to the flicker so i don't think that is it.

What else could cause the flicker ? connections? Have I bodged it too far ;~)

 

[McGlencoe]

Hi Johno,

The batteries are the stock units that came with the light: Ultrafire 26650 - 5000mAh 3.7v

I was wondering about a loose connection, but when screwed together with a fresh battery, you can shake the light, tap it and the light doesn't flicker at all.

However, when the light does start to flicker, you can rap it against your hand and it will stay bright a minute or two before starting to flicker again. Could this be from the battery or a connection that becomes loose? It isn't depth sensitive, meaning that there doesn't seem to be a problem at 30'/9m or at 90'/27m, only after the dive light has been on for 30-35 minutes.

 

[sharkbite]

My AUD$0.02...

The LED's themselves need "around" 3.6 volts to fire up properly - some more, some less depending on manufacturing tolerances...
the batteries start out at around 4 volts and drop to 3.6 before the protection circuit cuts in...

this does not leave much for the driver to work with (which also has tolerances) so it starts to "flicker" as the battery voltage drops...

Giving it a "gentle tap" either momentarily disconnects the battery, giving it an instant to recover, or the connection itself drops less voltage as the spring scratches into the battery terminal...

I think the single battery designs run pretty close to nominal for all the cheap LED torches - (i get flicker in all of mine - some earlier than others)
Running one with a power supply set to 4v will run all day and night with no flicker...whick kinda proves that theory

I reckon that carrying 2 of the cheapies is still an order of magnitude less expensive that a canister, with the "same" performance and none of the weight....

Hi Johno,

However, when the light does start to flicker, you can rap it against your hand and it will stay bright a minute or two before starting to flicker again. Could this be from the battery or a connection that becomes loose? It isn't depth sensitive, meaning that there doesn't seem to be a problem at 30'/9m or at 90'/27m, only after the dive light has been on for 30-35 minutes.

 

[McGlencoe]

Thanks for the info Sharkbite. I'm still learning about how these things work.

I'll take a multi-meter with me next time and get a pre and post dive voltage reading to see how much loss there is over a dive.

 

[sharkbite]

No worries - you should find a way to measure the voltage while the battery is under load - i.e. when the light is shining - the batteries will have a different voltage with no load.

cheers,

Thanks for the info Sharkbite. I'm still learning about how these things work.

I'll take a multi-meter with me next time and get a pre and post dive voltage reading to see how much loss there is over a dive.

 

[sharkbite]

Upadate! (sort of)

due to the performance/price equation i bought another one of these lights to make a video light for a small underwater HD camera.

i went with an ebay deal that came with a torch body, charger and 2 26650 batteries.

After a few uses, both the new torch and the old one started exhibiting the symptoms described by McGlencoe.

i put in some good quality 18650's and performance was restored.

I measure the voltage and current of both batttery types under load.

the 18650 manages to pump 1.7amps into the torch, and measures 3.7v under this load (4.2v unloaded)
the 26650's only manage 1amp at 3.5 volts despite measuring 4.2v unloaded.

The 26650s are actually capable of supplying around 6 amps before the protection circuit cuts in (measured using a rheostat as the load)
but even at a lowly 1 amp cant keep the voltage high enough to satisfy the 3.7 required to fire a t6 or u2.
so the internal resistance of the supplied batteries is too high....

the torch itself is fine - i am using 18650's in them for now (until my good quality 26650's arrive)

cant really complain - the whole kit only cost AUD$10 more than buying just the torch - and i still have a charger that works.

cheers,