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I am in the process of building a 50 watt umbilical dive torch.  The head unit is complete and I am looking at my options for the battery pack.

Currently I have 40 AA NIMH 1800mha batteries and am looking at the best option for putting them together as a 12v battery pack.  So far I am considering either using all 40 to give me approximatly 12v at 7.2ah or 2 packs of 20 to give me 12v at 3.6ah in each pack.

This raises the question of charging !!  I already have a charger for a 7.2v NIMH pack that indicates an output of 12v at 600mha.  Would this work for charging the pack(s).

Any ideas or advice appreciated.

Daz
 

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Hello,
I have a pack of 10 Nimh cells of 1.2V, 4100mAh. I use a Maha 777smart charger. One of it's good points is that has a temp. sensor so that cells do not over heat.Can you give more details of your charger, does it has a temp sensor, time limit or deltaV termination?

Regards

Pierre
 

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Hello again Daz,
With my pack 12V 4100mAh with a 35w gives me 65min. So I think that for a 50W you need a 7000mAh pack. Sorry if I am telling you the basics but if you run a 7.2Ah with a 50w halogen bulb you wil get the following.
Power W = Voltage V * Current I
50W     = 12V * Current ?
50W/12V = Current
4.17A
So if you divide power pack current by your current needed you get burn time but to get a more realistic value you have to multyply by 80%
So 7.2A divide by 4.17 = 1.73hours = 103min * 80% = 83min burn time, which is very good for a 50w halogen bulb.
 

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Pierre, can you give us a link to some pictures of your canister light, please. I'm sure you would make a few heads turn. It looks neat, well constructed and effective. Did you ever use those SS D ring holders on the canister? From what I already seen it is worth every minute that you put into it. Well done.

Lawrence
 

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Hi Pierre,

Thanks for the info on times.  I had roughly worked out that it would pull about 4ah and I thought that with this sort of current draw it would make sense to have the maximum capacity in the canister.  So I will probably put the pack together as 4 packs of 10 cells.  I can then connect the packs together to give me approx 7.2ah total capacity.

The time to charge is not to critical and I will look at the charger tonight to see if I can work out what type it is.  It does not do any temperature sensing, but I know it switches to a trickle charge.  It is definately a NIMH charger as it came with my 20watt torch which has the 7.2v nimh pack.  I do not believe it uses a timer as the time to switch from full charge to trickle charge varies depending on how much use the battery has had.  

I will see what info I can find and post.  Thanks again.

I am also quite interested in canister construction,  I have not got that far yet but any ideas are greatly appreciated.

Daz
 

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Daz
im working (slowly) on an umbilical torch. im hoping to make mine HID and have sourced the lamps/gear, i also have some lamps which are 50W halogen but give the same type of light as HID (4200, 5400 & 6500K) andy2tanx has tried one in his green force & seemed to like it.
i wouldnt mind having a look at your head unit & or canister as ive got all the internals pretty much sorted but havent made much ground on the head/canister
 

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Duncan,

Ok not very innovative I know, but I used a old maglight as has been used before (http://www.oneandoneis2.demon.co.uk/DiveWeb/diytorch.htm )  I already have a 20w umbilical but just fancied having a go at making one myself.

So far it has worked out exactly as said.  I am using a 50watt low voltage bulb.  I will take a picture of it and send it when I get chance.

I would be interested in a bulb with a temperature around 6000,  What type of fitting are they ?  

The nice thing about the low voltage 12v unit is that it really does fit straight in the maglight head.

Tomorrow I am making my switch assembly out of a relay and reed switch.

Daz
 

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Oh almost forgot,  I did cut the maglight down and using fimo plastic and araldite fixed the head unit to the stumpy end as recommended.

Daz
 

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And another question.  

I am considering some sort of wet connector on the cannister.  I was thinking of having a couple of connectors through the lid and equivilent plugs on the lead so I can disconnect the head of the torch easily.  Does anyone have any ideas on how to achieve this,  I believe by using a diode I can avoid the battery discharging in the water.

Daz
 

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Here is a link to my dive light <a href="http://groups.yahoo.com/group/hiddivelights/files/Pierre%20Malta%20Dive%20light%20Ver.%202/

The" target="_blank">http://groups.yahoo.com/group....e</a> canister is 40cm long * 50mm diameter with 2mm walls.
 

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Where can I find reasonably idiot-proof instuctions to build one of these. I've heard many people talking about them now, but I would need a recipe type format to follow i.e. A list of what to buy and how to put it all together. It would be an interesting Sunday project.

Peter  
 

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Peter

Treat yourself to this book, I have and it has everything you could want to know... my problem!! I haven't pulled my finger out of my arse and done anything it's told me yet but the book is top drawer, if you wanna build a light then this is the book for you

regards
Dave.

edit: whoops! now I'll add the link eh.... sigh..
http://www.airspeedpress.com/newlitebook.html

(Edited by Dave Williamson at 9:01 pm on Feb. 12, 2003)
 

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I did it myself, but I'm still putting finishing touches on the thing. I have found a perfect canister. 4" diameter, with o-rings, and you can make it any length you like with a length of soil pipe. All you need to complete it is araldite.

I don't know what batteries you've got there, but I'd say this canister is ideal for most uses, as well as the fact that at this size you can use buddy pony bands or 5.5" twinning bands to attatch it to your cylinder.

I'll send you my report of the project so far if you like, but I warn you that it's not finished. I'm getting around to it, and just need a few more photos, and somewhere to post the thing.

I don't knwo much about switches etc. so I opted for the Maplins waterproof option. I went for a small one, but I've seen these really hefty ones that look like you could easily use them with drygloves on. I go for wets, so I've got a more sensible size switch.

I would also suggest that if you've got a really new idea on what to use or how to use it, post it on the forum and I'm sure if anyone's tried and failed they'll let you know. I spent about £20 I didn't need to.

Mind you, the whole lot cost me £76 so far, and it's due it's first sea trial in Stoney on Saturday. If anyone's there on Saturday and wants to ask a load of questions, please come up and ask. I don't bite (unless you want me to), and I want other people to try this, too.
 

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Hey Digger,

Thanks for the offer of a heads-up on your obvious labours. Hope all goes well for the 'sea-trials' at Stoney and look forward to any pics (email to Heads Up (Jay)) you might have of the project.
 

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It leaked. The bloody thing leaked. I had to pour water out of the lighthead. Bugger. It still worked, even at the bottom depth, full of water. So, it might not be sealed, but maybe it doesn't need to be!

I know where it leaked, though. Between the face cap and the head. I think the glass I've used is too thick.

I'll do the repairs, and report back on the next test. I think it will be in a lake in Wales somewhere. Hodge Close quarry or something like? Anyone been there? All I've got to go on is a sign to say "Do not enter the cave system or you'll die, guaranteed." Well, something to that effect.

Bren, what is the e-mail address you want me to send the report to? I've got it down in Word at the moment, for want of something better, but you should be able to copy and paste it fairly easily.
 

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Hi Digger,

Sorry to hear about your slight mishap,  interested in your supplier for the canister, most of the pipes with 'o' rings I have looked at seem about 6" in diameter.

I used 3mm glass on mine, maglight with a 12v low voltage halogen unit inside.  It seems water proof to 18m so far.

Cheers,
Daz
 
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