Dive computer battery and o-ring spec's

[guidito_ito]

hi, thanks for all the info that was posted here. sorry to revive it too but I need the oring specs for the oceanic transmitter, does anyone have that? I have the OCI and got the specs from here (140x1.5x70NBR) but I need that other one. I found a cheap supplier in the UK btw 140 x 1.5mm Nitrile 70 O'Ring (10x) | eBay

 

[alphakry]

this thread is awesome and needs to be revived now and then. anyone have something new to contribute?

any updates?

 

[Dave in SD]

Does anyone have information on the o-rings for a Hollis TX1 He computer and transmitter? The batteries are listed in the manual: 3V CR2450 Lithium Battery for the computer, 3V CR2 Lithium Battery for the transmitter.

 

[tech3324]

FYI: I just ordered replacement o-rings for two computers from The O-Ring Store LLC, We make getting O-Rings easy! They seem to accept small orders (5x o-rings) but minimum shipping looks to be $6. I have no connection with them, just a google search.

Post up other sources for small quantities if you have any recommendations.

 

[Bert van den Berg]

Puck wrist - cr2450. Don't really know why you have to replace the O'ring. The battery gets changed so infrequently that the O'ring should last forever. Just pull it out, clean it and lube it with a (small) amount of silicon grease.Been doing this for years and no problems.

 

[alphakry]

Puck wrist - cr2450. Don't really know why you have to replace the O'ring. The battery gets changed so infrequently that the O'ring should last forever. Just pull it out, clean it and lube it with a (small) amount of silicon grease.Been doing this for years and no problems.

the reason is because it's a static crush o-ring that is meant to be crushed in place to create and secure the seal. most of these o-rings are so large and thin that once it sees this type of action, it can be changed forever from it's NEW state and hence runs a risk of it not sealing again properly. This is true after only 1 time, so the risk increases substantially if being re-used multiple times.

In the example of the crush static o-ring on a regulator hose, reusing this o-ring is a minimal risk thanks to a worst case scenario of either a pressurized reg set having air present to push air out and prevent water coming in - or even if a minimal amount of water gets by the o-ring, it's an easy procedure to remove that water with no damage. This isn't the case with a much more sensitive computer and the constant pressure it's under with water always wanting to get in...

Your Mileage May Vary, but do understand you are taking a risk significantly higher then zero every time you reuse a computer o-ring and that risk comes with a pretty high cost of error. Sure, it may have no problem at all... and typically doesn't. But at such a low cost, is it worth the risk? Not everyone answers the same and me as a professional absolutely doesn't want the burden of a $500 dead computer because I didn't bother to replace a $0.50 o-ring. Especially if it's someone else's computer.

 

[Fibonacci]

Really great o-ring research but I don't see Suunto D4i listed in v1.5..
A web search revealed one listing of ID 39.0 x 1.5mm EPDM 70 DURO
However Oceanic OCS are supposed to take the same size o-ring but the chart lists them as ID 40.0 x 1.5mm
So which one is correct?

 

[Scubagaskets]

I can only confirm that 39 x 1.5 o-ring is for suunto D4i C8 D4 and OCS And OCI of Oceanic .

 

[Fibonacci]

I can only confirm that 39 x 1.5 o-ring is for suunto D4i C8 D4 and OCS And OCI of Oceanic .

Thanks SG... but there still seems to be some inconsistencies here.
An earlier poster contacted Oceanic Singapore and apparently they said the OCS o-rings are ID 40.0 x 1.5mm
The only way to double check the Suunto D4i o-ring spec of ID 39.0 x 1.5mm is to measure the case recess, the cover and the groove then work from there. I don't have these dimensions right now.
There is an excellent o-ring size calculator and some design guides that I use for my vintage pneumatic speargun restorations here:
O-Ring Gland Calculator - Engineering Tool for Dynamic Applications | Apple Rubber Products

 

[Fibonacci]

the reason is because it's a static crush o-ring that is meant to be crushed in place to create and secure the seal. most of these o-rings are so large and thin that once it sees this type of action, it can be changed forever from it's NEW state and hence runs a risk of it not sealing again properly. This is true after only 1 time, so the risk increases substantially if being re-used multiple times.

Very true, I've seen this on my GF's D4i... because the o-ring is large in diameter with a very thin cross-section it tends to twist slightly as it is compressed by the case cover vs the much thicker cross section o-rings generally used in SCUBA applications.
Viewing a used D4i o-ring with a loupe, you can clearly see slight helical witness lines along its axis. If these o-rings are left in place longer and the witness lines become deeper its quite possible a certain random new orientation will permit water ingress if they are reused.
I got away with it once, but will replace the o-ring with every battery change now