bugger -cracked electronics pod cap/ rear display! :-(

Drmike

bugger.

As usual left it to last min to begin getting gear together for trip (next week to Philipines).

Boris is not smelling too fresh - must have put it away damp
batteries totally flat so pop new set in.

anypoo...

as im changing batteries I notice the rear display (electronic cap) is cracked!

Bugger bugger bugger.
bugger.


Its a good crack. It looks like the crack initiated from the area around the lower wetswitch bolt head

i did note the batteries had leaked and were flat - can a faulty leaky battery generate enough pressure to crack the cap from the inside??? or maybe i damaged the cap while moving my unit around....bugger

its strange - but i am 100% sure there was no crack when i put the unit away last time (its a big crack and hard to miss)

sooooo lesson to learn - if your using the old style rear display* (one with wetswitches) have a reg check for cracks

*pressume new model with auto breathe start up doesnt have the wetswitch bolt.

electronics still work (and the rear display has also come back to life) - but the crack clearly will cause a flood if i dive it

jaap

What sort of batteries are used? Alkaline C type cells?

Looks like they can generate quite a lot of gas on a deep discharge:
Energizer Design Considerations - Hydrogen Generation

They abusive charge value really looks scary!

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My initials: JAAP

Drmike

Thanks for that link

yup C cells.


given the volumes in the battery compartment that much off gassing (assuming normal deep discharge) would result in roughly a 3 times increase in the internal pressure. I suspect the design can handle an internal delta P of 2 bar though but without doing a FEA on the design can say for certain as its not a simple shape internally. Given that it can handle a delta P of 20bar or more from outside I suspect battery off gassing was not the cause although of course that doesnt necessarily prove anything when pressure gradient goes the other way

pic of offending crack

- guess i must have twatted it at some stage (read: dragged it up side of some cave)

the newer models dont have wetswitches, [the bottom one looks to be the initation sight of the crack (perhaps from contact with something) ] so newer models should be more robust. (I have never dropped the unit - only a bit of light dragging)

Attached Images

DSC05372.JPG (320.8 KB, 14 views)

jaap

Perhaps not very likely, but is there a hydrogen/oxygen catalyst built into the pod?

If not perhaps there was a small hydrox explosion? Even though some good old impact damage looks like the most likely cause.

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My initials: JAAP

richc

I think that the internal pressure is unlikely to crack it. I can offer you 1 data point on this - I flooded my Boris battery pod about 12 months ago. Entirely my fault as I pinched the O-ring during a battery change. It felt odd tightening it up but foolishly I was in a hurry and so didn't re-check it (doh!). At 60m it flooded and subsequently the batteries leaked acid everywhere. The gas couldn't escape fast enough as was evident 2 hours later on the surface when it was still under pressure in there as I unscrewed the cap. No cracking but despite rinsing with fresh water ASAP and drying, the electronics were unhappy and it had to go back to the factory to be sorted (fortunately covered by the insurance). Not suggesting you try it, but my experience was that the unit could run a 2 hour dive with a flooded battery pack and no loss of functionality. Didn't even get a low battery warning. The only sign on the dive was that the rear display stopped working.

Rich