Using Silicone instead of O-rings?

[rbchtt]

Hello,
I an working on a small diving light project.

Is that a good idea using silicone instead of O-ring for sealing?

 

[Tropicalwolf]

It would depend on whther or not you need to disassemble they item at that "point." I would lean toward o-ring, just for simple/ease of replacement. Just my 2 cents.

 

[miketsp]

As already stated it depends whether you want to open it again or not.
Some years ago I built a canister light that was permanently sealed with silicone. This really simplified construction.
It has a rechargeable 9AH battery and the charging terminals are external with one of them connected via a diode to stop reverse current flow and electrolysis.
It works perfectly and will only need to be opened if ever the bulb blows or the battery comes to the end of its working life.
The only problem I ran into is that I can't fly with it.
Airport security won't pass anything that is can't be opened for inspection.
So I only use it for dives that I can drive to.

 

[haibeis]

miketsp - i considered making a sealed battery canister in this way....am still thinking about it....and the fact you built yours "some years ago" tells me this is not a bad idea!

(i was going to put some nimh in some pvc pipe and completely fill the air gaps with silicone)

one thing that concerns me is the potential for it to pop or explode due to (maybe) some gases given of during charging....?

what kind of battery are you using? (SLA/nicd/nimh/Lithium)?
do you have air space inside the canister, or some other way of relieving the pressure?
do you get said pressure at all?
how quickly/slowly do you charge it to avoid the big "boom"?
how often do you use it?
any photos taken during construction?

most curios, as this method completely takes out of the picture the complications around o-rings and glands etc...

 

[haibeis]

miketsp - i considered making a sealed battery canister in this way....am still thinking about it....and the fact you built yours "some years ago" tells me this is not a bad idea!

(i was going to put some nimh in some pvc pipe and completely fill the air gaps with silicone)

one thing that concerns me is the potential for it to pop or explode due to (maybe) some gases given of during charging....?

what kind of battery are you using? (SLA/nicd/nimh/Lithium)?
do you have air space inside the canister, or some other way of relieving the pressure?
do you get said pressure at all?
how quickly/slowly do you charge it to avoid the big "boom"?
how often do you use it?
any photos taken during construction?

most curious, as this method completely takes out of the picture the complications around o-rings and glands etc...

 

[haibeis]

......

 

[miketsp]

miketsp - i considered making a sealed battery canister in this way....am still thinking about it....and the fact you built yours "some years ago" tells me this is not a bad idea!

(i was going to put some nimh in some pvc pipe and completely fill the air gaps with silicone)

one thing that concerns me is the potential for it to pop or explode due to (maybe) some gases given of during charging....?

what kind of battery are you using? (SLA/nicd/nimh/Lithium)?
do you have air space inside the canister, or some other way of relieving the pressure?
do you get said pressure at all?
how quickly/slowly do you charge it to avoid the big "boom"?
how often do you use it?
any photos taken during construction?

most curious, as this method completely takes out of the picture the complications around o-rings and glands etc...

PM sent with photos and sketch.
These show it as initially constructed, later I added a rigid handle to ease use.

Just a couple of general tips.
There must be air space inside canister. You must not subject the battery to ambient pressure or there is a danger of shorting out the plates and generating a bomb.
I did later drill and tap the back plate to put a venting screw just as a precaution.
Loose for storage and charging, tight for diving.
12V 9AH sealed lead acid battery.
Small constant voltage 12V 500mA charger bought commercially.
One charging terminal isolated via a diode to avoid electrolysis at terminals while diving - current can go in but not come out.
One of the magnetic switch positions operates a relay that can short out the diode while charging.
External magnet operates internal reed switches that operate lamps via soft-start CMOS switches.

 

[bleeb]

one thing that concerns me is the potential for it to pop or explode due to (maybe) some gases given of during charging....?

Be aware that some battery chemistries can sometimes offgas while discharging, whether they're rechargeable or not. For example, some manufacturers recommend against using certain products in sealed housings like those used for diving because they can generate hydrogen gas under certain conditions. (Damage from the shock of having been dropped on the floor recently can be one of them. They're not talking about a huge explosion, just enough of one to pop the seals and flood the thing.) Personally, I think the risk is low enough to use them routinely, but it would suggest not permanently sealing things and maybe opening during charging.