Narked at 90 fourth cell conversion

Another review that only impacts rebreather dives I'm afraid!

As your experience on 'the box grows you learn that the initial mantra of 'if there is a problem bail out and abort' isn't necessarily true in all cases, for sure in many circumstances with a non-flooded loop it is better to fly manually or use your system in SCR mode if only to minimise the gas you carry. This bit of kit will help you in these scenarios!

To be able to monitor your loop via second display/computer you need to break into the existing circuit and ideally have an additional cell, this kit from Narked at 90 with parts also delivered from their associated US company Add Helium allow you to do this without cutting into wires which would invalidate any warranty on your unit.

The kit consists of a wiring loom, with a fischer connector at one end allowing the cells to be plugged directly into a computer of your choice, be that a Shearwater, VR or other technical diving computer. Mid-way down the cable is a gland and at the other end cell connectors of your choice so molex or co-axial. There is also a little bag of bits with some three way connectors or cell splitters, grease, etc.

I looked at this bag of bits and was baffled, how does it fit, did I need to drill a hole? So I went back onto the Narked at 90 web-site and read the spiel again and the truth dawned, I also needed a new APD 4 cell holder, a part which despite being on the site had to be bought from the USA. I can only guess that AP got 'arsie' about another supplier selling a kit that improved their unit and made threats, maybe I'm mistaken and it's all about approvals but......


The '4th cell holder' from the US, still has the narked at 90 sticker though!

So having got all the bits I very easily and quickly put it together, cells 2 and 3 were fitted with the 'cell splitters' with cell 1 and 4 connected to only one computer. So with the existing controller connected to the three 'original' cells and piggy-backed shearwater system connected to cells 2,3 and 4, the new cell I fastened everything back together and then switched everything on......the rebreather, the shearwater, the lot! I expected error messages and problems galore.


An overview of the wiring with cell splitters, it's a bit busy in there!

There were none! The AP system went through the normal boot up cycle and the shearwater displayed acceptable values, wow great. I calibrated the shearwater at the same time as the AP and everything went swimmingly, so it was into the pool to play.


Gold platted cell splitters ensure that cells can be used by two computers.

I started looking at fault scenarios and simply switched off the AP system, the shearwater continued to operate and display accurate values as I carried out various purges with oxygen, air and a few nitrox mixes. Happy that I could fly the unit from the shearwater I then switched on the AP system, allowed it to boot up and switched off the shearwater with no impact, great!

Diving with this system can be interesting as you have an extra cable and computer, some friends secure their computers 'back to back' with the AP unit and then cable tie the leads together, this works and means that everything is together and to hand. I prefer to have the shearwater on my left hand and the AP unit clipped to the harness, simply because I find the shearwater display 'better', or more intuitive, it tells me everything I need to know and I can see and hear if the AP system has an issue via the HUD and buzzer unit.

My only comment should you decide to follow my method is that you must loop and lock the cable around your forearm to minimise the risk of the cable snagging and pulling free the fischer connector, simple, effective and potentially money saving! 

So would I recommend that you purchase and install this system, yes a resounding yes! There are a couple of points, it's a bit of buggeration getting all of the bits but providing that you can live with a two week delivery timescale, not a problem.

The other issue is that if you ever send your head back to AP they haruuuumph and won't reassemble parts that aren't supplied by them so you have some work to do at home if you send your unit to Cornwall, my advice is to learn how to service your own unit!

Richies ratings : 9/10 a shame about the bit from the USA, apart from that near perfect

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