So I was thinking about building a deep water camera housing. The housing would be filled with a non-conductive fluid to counter the pressure at depth.

Although fluids like purified water or propylene glycol (anti-freeze mixtures) are stated to be non-conductive, they become ionized when in contact with metals and plastics, thus gradually conducting electricity again. There are ion-exchange resin products that are supposed to keep the fluids de-ionized though. Source: https://www.electronics-cooling.com/2015/12/tech-brief-low-electrical-conductivity-liquid-coolants-for-electronics-cooling/#

So while the electronics might survive being emerged in liquids for a day, what about the 3V lithium batteries that power the camera? Do you expect this thing blowing up in my face in any case, or is there a possiblity that this might work?

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    \$\begingroup\$ Some interesting info: Exposure of lithium batteries to external hydrostatic pressure: ffi.no/no/Publikasjoner/Documents/… \$\endgroup\$ – user3002097 Mar 16 '18 at 15:43
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    \$\begingroup\$ Transparent mineral oil is also a choice. \$\endgroup\$ – Janka Mar 16 '18 at 15:45
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    \$\begingroup\$ @user3002097 where would the oxygen come from for combustion if it's underwater? And propylene glycol is flammable \$\endgroup\$ – Chris H Mar 16 '18 at 15:58
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    \$\begingroup\$ Thanks a lot for the clarification, I will take this into account. I'm concerned about the stuff going off on the surface, like in the back of my car when travelling to the lake. \$\endgroup\$ – user3002097 Mar 16 '18 at 16:15
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    \$\begingroup\$ @user3002097 What's your rationale for using lithium chemistry? Would you consider batteries with a more docile chemistry? \$\endgroup\$ – Nick Alexeev Mar 16 '18 at 17:25

My recommendation would be;

Lithium Sulfuryl Chloride (Li/SO2CL2)
or Lithium Thionyl Chloride (Li/SOCL2) cells
- only in a Stainless Steel case
- with the unit sealed in Aflas 7182B polymer O-rings.

Criteria; highest energy density with a flat voltage in the strongest high pressure proof case sealed resistant to aggressive chemicals, caustics, high pH, high pressure.

LiPo cells rupture explosions have been well documented under high pressure

  • \$\begingroup\$ ... and no explanation as to why one should go to each of these lengths. \$\endgroup\$ – Nick Alexeev Mar 17 '18 at 0:21
  • \$\begingroup\$ ok ok .......... \$\endgroup\$ – Sunnyskyguy EE75 Mar 17 '18 at 0:27

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