Electronics > Manufacturing & Assembly

Encapsulation for ATEX

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Gribo:
It was a Kokam small cell, Sadly, Kokam is no longer making small cells. The PN was SLPB544032, it had a carbon anode, so no leaks, no ignition. There are now equivalent parts from other manufacturers (Varta) that have similar certifications.
The trick was Zener diodes for voltage limit, 2x 4.7V Microsemi SMBJ5337 (obsolete, leaky) and 375mA fuse for the current limit. Today I would use 2 5.1V Zener diodes, and a smaller 315mA fuse.


voltsandjolts:
I noticed the IS ATEX IIC T4 certified Keller Leo Record Ei uses one 2.2Ah Tadiran SL760 AA 3.6V Lithium Thionyl Chloride primary cell which is not potted and is user replaceable.

The cell has rated nominal discharge current of 2mA with continuous discharge currents of 100mA and a pulsing current draw of 200mA.
I've never tried shorting it out, but to me it sounds capable of generating an energetic spark...but I must be wrong of course :-//

tszaboo:

--- Quote from: voltsandjolts on December 20, 2021, 03:41:58 pm ---I noticed the IS ATEX IIC T4 certified Keller Leo Record Ei uses one 2.2Ah Tadiran SL760 AA 3.6V Lithium Thionyl Chloride primary cell which is not potted and is user replaceable.

The cell has rated nominal discharge current of 2mA with continuous discharge currents of 100mA and a pulsing current draw of 200mA.
I've never tried shorting it out, but to me it sounds capable of generating an energetic spark...but I must be wrong of course :-//

--- End quote ---
For batteries, the testing is to determine how hot they get in case of an internal short circuit. That's the T4 part. And maybe they can create a spark, but in case the spark energy is low, it is not going to ignite the gas most of the time (which is in the order of parts per billion in this case).


--- Quote from: Gribo on December 20, 2021, 02:47:40 pm ---It was a Kokam small cell, Sadly, Kokam is no longer making small cells.
--- End quote ---
Thank you. Unfortunately, the newer cells are quite problematic, since the goal for cell development is to lower the ESR, and to make the battery lighter.

voltsandjolts:
Ahh, OK, so energy in the heat source or spark must be far below the Minimum Ignition Energy rating for the specified environment.
How do you calculate the energy in a spark from a battery or capacitor shorting?
For a capacitor do you just use the stored energy 0.5*CV^2 ?
For a battery?

tszaboo:

--- Quote from: voltsandjolts on December 20, 2021, 04:33:25 pm ---Ahh, OK, so energy in the heat source or spark must be far below the Minimum Ignition Energy rating for the specified environment.
How do you calculate the energy in a spark from a battery or capacitor shorting?
For a capacitor do you just use the stored energy 0.5*CV^2 ?
For a battery?

--- End quote ---
There are specific rules defined in IEC 60079-11 that define the applicable conditions, if a circuit or a component or certain voltage and current is safe or not.

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