The Inon Black Disc - A Strobe Mystery

Inon strobes have a black plastic disc on the surface of the battery compartment. The disc is on the bottom of the battery compartment of the D2000, D200, Z240 and Z330 strobes, and on the side of the S2000 battery compartment. It is not mentioned in the User manuals, and as far as I know, is anonymous, bears no logo, does nothing and causes no problems. It has no personality, it is just there.

Some have speculated it may be a pressure relief valve.

Recently I have examined some old and some flooded Inon strobes and found that the black disc was not damaged, loosened or affected by age or flood water, and had not functioned as a relief valve.

What then is the function of this black disc? It does not move, cannot be unscrewed or pried off and is not connected to a structure or working strobe part. It is not a base plate for the vertical screw rod inside the battery compartment, as it is not connected to, or even aligned with the base of this rod. There is no inside hole for it to plug or act as a valve. It just exists as a flat, round, black plastic disc.

To me the reason for, or function of, this Inon strobe black disc is a mystery.

Could it be an ornamental medallion?

What am I missing?

What is the guess or opinion, casual or informed, of the Wetpixel experts?

It is a sonic transmitter that sends out a signal when the strobe batteries are too depleted to fire that and marine subjects are now free to swim about.

A similar device was integral to film cameras and activated when the 36 th. frame was exposed.

Thanks! I'd always wondered about that....

Here you are:

http://wetpixel.com/articles/show-report-adex-2018-by-drew-wong

scroll down to the response from the INON rep:

"Takuya Tori San of Inon Japan, was also on hand to quell fears of Inon strobes “in”-compatibility with Eneloop batteries. He told me all Inon strobes have an off-gas valve, which allows the dangerous gas to vent when the battery discharges in use."

Here you are:

 

http://wetpixel.com/articles/show-report-adex-2018-by-drew-wong

 

scroll down to the response from the INON rep:

 

"Takuya Tori San of Inon Japan, was also on hand to quell fears of Inon strobes “in”-compatibility with Eneloop batteries. He told me all Inon strobes have an off-gas valve, which allows the dangerous gas to vent when the battery discharges in use."

Ok, if that is what the black disc is for, then what is it that tells the fish to come back when the batteries are dead?

The mystery of the Inon Black Disc is solved, thanks to Tiger Shark, above. If one looks closely into the Inon D2000 strobe battery compartment one finds at the bottom a tiny, about 1 mm, hole with a shiny metal device in it centered on the outer black disc. This is said to be a vent for gas, such as hydrogen, released by a “hyper-electric discharge or short circuit" of Eneelop batteries (1).

There are two shiny steel devices visible in the bottom of the D2000 battery compartment, the one on the right sits inside a small hole, and the one on the left is on the surface. Both may be gas pressure detectors, but are not described in the Inon User Manual.

About this “hyper-electric” (whatever that may be) discharge, here is what Pansasonic recommends: “Please do not use eneloop Ni-MH batteries in underwater lights or other airtight appliances” (1).

Clearly, many underwater photographers neglect to follow this expert hyper-electric advice.

Unfortunately the Inon gas-release device does not prevent water flooding from the battery into the electronic compartment. For this, future, properly engineered water proof seals between the two compartments will be necessary.

Citations:

1. https://www.panasonic.com/global/consumer/battery/eneloop/technologies.html

"Can eneloop be used in underwater lights?

Please do not use eneloop Ni-MH batteries in underwater lights or other airtight appliances. Ni-MH batteries feature a gas vent that allows the release of hydrogen when the battery is misused. Gas will not be released under normal usage conditions, but hyper-electric discharge or short circuit can cause internal gas pressure to rise and gas to be expelled. This gas contains hydrogen and sealed devices can’t diffuse the gas, so any source of ignition may potentially cause fire.”

- -

At Adex 2018 there was more on the Eneloop batteries:

http://wetpixel.com/articles/eneloop-batteries-not-recommended-for-use-in-strobes

followed by a report of the Seacam’s adaptive electronic controller to recharge batteries, and a comment on the Inon off-gas valve:

http://wetpixel.com/articles/show-report-adex-2018-by-drew-wong

--

In case you are wondering about Hydrogen, it is the best fuel known, lightest, odorless, colorless, non-corrosive, non-toxic and easy to obtain, except it is explosively flammable and difficult to store as it seeps out of most containers, good reasons why it is rarely used, particularly after the Hindenburg tragedy of 1938. It seems like good practice to open one's strobes away from any fire or person smoking.

Hindenburg dirigible on fire, 1938 newsphoto from Google

Is the problem just Eneloops, or is it all NiMH rechargeables? If the latter, what is suggested to use instead? I do NOT want to go to disposable alkalines....

Good point. Wikipedia has an relevant article on the Nickel–metal hydride battery. It reads :

"NiMH cells have an alkaline electrolyte, usually potassium hydroxide. The positive electrode is nickel hydroxide, and the negative electrode is hydrogen ions, or protons. The hydrogen ions are stored in a metal-hydride structure that is the electrode. Hydrophilic polyolefin nonwovens are used for separation."

All Ni-MH batteries use the same chemistry, but may well use different materials for separation.

Released hydrogen gas seems to be what causes trouble, but it also a very rare problem as practically nobody knows of or has had a strobe fire. None that I personally know, none on Wikipedia to my knowdege.

Hydrogen is non-toxic and dissipates instantly as it is so much lighter than air, the amount that could possibly be released is very small. For prevention, a reasonable approach is to open one's strobes at a distance from smokers or an open fire.

The use of eneloops has been discussed before with regards to the Panasonic warning. I maintain this comes from the lawyers if you listen to them you might as well stop taking anything electronic underwater no battery currently available likes salt water and I believe any one of them is capable of producing hydrogen. You are storing quite a bit of energy in a very small space and you need to keep it dry. Basically your options are Li-Ion or NiMH and nether like water and especially not salt water.

The battery compartment is sealed with o-rings. You will note that page 50 of the user manual Z-240 - basic operation that INON recommends replacement of all o-rings every 3 years - I doubt this happens very often given that service is not always easily obtainable. This post also refers to causes for leaks: https://www.scubaboard.com/community/threads/flooded-inon-urgent.356273/. It makes sense that if o-rings are older or perhaps have been impacted by contact with chemical soup coming out of the battery for too long that they might leak. The are likely butyl rubber o-rings which give good service in salt water, but perhaps not so good with various chemicals and like all rubbers slowly oxidises with age. Also not the potential for cracking of the case in contact with the remains of the batteries.

Everyone uses Eneloops in Inons. I have for at least 10 years. I just finished a trip and like five people had Eneloops in Inons. No underwater explosions reported.