OP
martzak
Contributor
Looks pretty good. I'm assuming it's a sealed canister design...correct? That may be the way to go. What kind of a switch do you use? reed?
diy dive light canister, less expensive option
- Thread starter martzak
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Looks pretty good. I'm assuming it's a sealed canister design...correct? That may be the way to go. What kind of a switch do you use? reed?
DIWdiver
Contributor
That's a cute cannister, Willem. Certainly didn't require any fancy tools!
I'd steer clear of home center window panes. They are almost certainly acrylic, which is great for windows, but try and put a screw in it and you will find out how poor a material it is for this purpose. If you don't believe me, get a piece, drill a hole in it, and screw it to a piece of wood. Tighten the screw enough to seat the plastic firmly against the wood. Looks great right? Now set it on the shelf for a couple of days. When you come back it will have a multitude of cracks radiating out from the screw.
Polycarbonate (PC) can do this too, but it takes a lot more force. Most other plastics won't do this.
Getting lids of 1" PC for $25-30 seems like a bargain. I just looked at Industrial Plastics, and there are several decent options, but PC is twice the price of the next, and almost 10 times PVC!
I figure 3/4" is plenty thick, as the smaller diameter only needs to be thick enough to hold the o-ring and center the lid in the tube. 3/4" x 12" x 12" sheets at IP are currently:
Polycarbonate - $117
Acetal (Delrin) - $58
Nylon (non-specific) - $51
ABS (non-specific) - $28
PVC (non-specific) - $13
The PVC doesn't even meet their minimum order of $20.
Hacker's Haven (AKA McMaster Carr) prices are substantially higher, though they will sell smaller pieces and have no minimum order.
My preference would be PVC or acetal. PVC because it's cheap, and acetal because of its strength and easy machinability. If you were planning on beating the crap out of it, maybe nylon because it will NEVER crack. My buddy is making and selling nylon jump reels for cave diving because the delrin ones are breaking. I would only use PC if it must be clear for some reason.
I'd steer clear of home center window panes. They are almost certainly acrylic, which is great for windows, but try and put a screw in it and you will find out how poor a material it is for this purpose. If you don't believe me, get a piece, drill a hole in it, and screw it to a piece of wood. Tighten the screw enough to seat the plastic firmly against the wood. Looks great right? Now set it on the shelf for a couple of days. When you come back it will have a multitude of cracks radiating out from the screw.
Polycarbonate (PC) can do this too, but it takes a lot more force. Most other plastics won't do this.
Getting lids of 1" PC for $25-30 seems like a bargain. I just looked at Industrial Plastics, and there are several decent options, but PC is twice the price of the next, and almost 10 times PVC!
I figure 3/4" is plenty thick, as the smaller diameter only needs to be thick enough to hold the o-ring and center the lid in the tube. 3/4" x 12" x 12" sheets at IP are currently:
Polycarbonate - $117
Acetal (Delrin) - $58
Nylon (non-specific) - $51
ABS (non-specific) - $28
PVC (non-specific) - $13
The PVC doesn't even meet their minimum order of $20.
Hacker's Haven (AKA McMaster Carr) prices are substantially higher, though they will sell smaller pieces and have no minimum order.
My preference would be PVC or acetal. PVC because it's cheap, and acetal because of its strength and easy machinability. If you were planning on beating the crap out of it, maybe nylon because it will NEVER crack. My buddy is making and selling nylon jump reels for cave diving because the delrin ones are breaking. I would only use PC if it must be clear for some reason.
DIWdiver
Contributor
It's generally considered a bad idea to charge batteries in a closed environment, i.e. in a light canister.
If all goes according to plan, the only gas generated is re-absorbed internally to the battery. No problem.
However, if something goes wrong, the gasses that will be vented are hydrogen and oxygen, in the perfect explosive mixture. Do you want to find out that this happened when you are at 180 feet and the wire finally corrodes through and causes a spark inside your canister?
Better to open the canister when charging.
D
If all goes according to plan, the only gas generated is re-absorbed internally to the battery. No problem.
However, if something goes wrong, the gasses that will be vented are hydrogen and oxygen, in the perfect explosive mixture. Do you want to find out that this happened when you are at 180 feet and the wire finally corrodes through and causes a spark inside your canister?
Better to open the canister when charging.
D
OP
martzak
Contributor
I agree. Venting your canister during charging is necessary. But instead of a lid I'm thinking about adding a simple hole to the otherwise sealed container. It's a lot easier to make a bolt size hole watertight.
Codiak
Contributor
Yep, but that was one of a couple options on that page... the BCA298 sells for under $50 and is what I used after crushing an Otterbox.
Airspeed's book has a lot of good ideas and info but it boils down to how much you want to do a hands on project versus cost.
With the drop in prices and increased performance of LEDs I'm tempted to just go the commerical route next time around
Airspeed's book has a lot of good ideas and info but it boils down to how much you want to do a hands on project versus cost.
With the drop in prices and increased performance of LEDs I'm tempted to just go the commerical route next time around
willembad
Contributor
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The can is sealed other than for battery maintenance - not regular charging though. Can any of you point me to documentation that states that Li-Ion chemistry needs an open vent during charging? I know the cells - my post should read 18650's, but I can't find the edit button - are designed with a overpressure vent but it is not open to atmosphere during any phase of normal operation. If these cells vent I'm pretty sure Salvo would like to know about it as well, since they manufacture a really slick slimline can for their led heads that is sealed as well.
The light switches with a small reed in the head that switches a mosfet. Works really well and no openings to outside.
Willem.
The light switches with a small reed in the head that switches a mosfet. Works really well and no openings to outside.
Willem.
rescue15
Contributor
I was told by a plastics manufacturer to stay away from nylon if you want water proof...PVC is best for the canister with a poly carb lid to be able to visualize if you have a leak.
Steve
Steve
Under normal conditions no vent is needed - as you mentioned the cells are already completely sealed. I'd think for safety you would want a vent though, as what happens if the cell vents into a sealed container? Or say your charger becomes defective and a bunch of cells vent. Again going into a sealed container might not work quite so well!
I've charged li-ion cells with just a current-limited bench supply before, so if you have a real charger you might be better off ;-) And also if you build some protective circuitry inside the can, of course that would help too.
-Colin
DIWdiver
Contributor
I just found that 1/2" PC sheets are about 1/6 the price of 3/4" thick sheets of the same size. Can anyone explain that?
D
P. S. I see that there have been a lot of hits on my profile page, so I just filled it in!
D
P. S. I see that there have been a lot of hits on my profile page, so I just filled it in!
rescue15
Contributor
Probably for the same reason longer flawless pine boards are so much more expensive...It's harder to get a perfect product.
Steve
Steve
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