Canister light without canister

[swedish diver]

I just built my own canister light ...without canister. I just took the lead accumulator, connected the necessary wiring and expoxysealed the wires. I dove it to 35 m today, and it worked out just splendid. Switching is implemented by a reed in my homemade lighhead (which also carries my home-made HID-ballast). This way, the only thing which "can" fail is the lighthead. The new "canister" is more sleek than traditional designs, and also incorporates less pointy parts (i.e. excenter locks etc) which can entangle.

Would like to hear if you think this is "the new way of doing it" or just stupid. Personally I can see no disadvantages.

/Kristian

 

[Iguana Don]

You could post a pic of your light so we might be able to understand exactly what you did.

ID

 

[jonnythan]

Is there any chance that there can be water seepage into the battery itself due to the pressure? Are you sure that battery casing can take dive after dive at 3 atmospheres of water pressure?

Sounds like a decent idea, but I would think the canisters are there for a reason... I wouldn't want to tote around a lead battery every dive, the acid in those things can be pretty harsh I believe.

 

[nickjb]

What type of Lead Acid battery are you using? I expect it is a sealed gel Lead Acid (SLA). These have a pressure relief valve that stops the battery exploding if it is over charged. It is best not to seal over this valve unless your charging is VERY well controlled. Exploding an SLA is quite nasty.

On a small rectangular SLA this valve is set at around 5 psi, on a more industrial battery it would be around 50 psi (Albeit in the opposite direction). The shell of the cell is probably flexible enough to keep internal and external pressure equalised so this shouldn't be a problem.

I have seen a similar concept for using nicads/niMH without a canister and relying on the case of each cell to withstand the pressue. My favourite was stacking the cells up in a plastic tube and sealing the ends with a bung and jubilee clip. Again, these cells have a pressure relief valve that must be taken into account.

 

[swedish diver]

The battery I use, is - as you said a sealed lead type. The 'housing' is PVC and the OP-valve is simply a piece of PVC, which - when / if excess pressure is built up inside the battery - is pushed out.

In case this happens, the acid would leak into the water. Not flood out however, since it's trapped it is normally absorbed by fiber wool which fills the battery. I've tried this (on purpos) and all that happens is that the battery get's a bit warmer - you could also notice small bubbles of gas forming nearby the valve.

Water pressure cannot push in the 'valve' - it can only be pushed out. This makes ascents the most critical point of any dive with my design.

Finally, the batteries are of a local brand. However, similar units should be avaliable also in the US.

 

[The Chairman]

ballast, and the battery set up... like IGgy said... lets see some pictures!

 

[swedish diver]

Ok, pictures are coming as soon as i have the time taking them, then borrowing a scanner and scanning. Until then, I'll draw the ballast schematics and post them together with some other essential stuff. Hopefully it will be done this weekend.

The material costs for the ballast was about $10. Probably it consumes more power than a comersial, but what the heck. Also, the transformers must be wound, but don't worry, all parts can be found at radioshack, digikey etc...

 

[swedish diver]

Currently i'm on vacation, but hang on... i'll post the stuff as soon as i get home again

See you all then

/Kristian

 

[scubaturek]

Patco has been making canister-less lights for a few years. Although they rate their lightheads for 500ft, the battery packs are only rated to 160. They now make a canister that's rated to 500ft.
Patco

Kristian, did you use the ballast plan from Jonathan Smick?

Joe