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DECO 40m Battery and Upgrade for Poseidon Rebreather MKVI

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DECO 40m Battery and Upgrade for Poseidon Rebreather MKVI

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DECO Battery and Upgrade for Poseidon Rebreather MKVI


The Poseidon MKVI Descovery can be updated to a 40m DECO Rebreather by simply changing the battery unit. You can get a 40m Deco Air battery and a 48m Trimix Battery.

We can only supply these batteries/upgrades to qualified, certified divers or to your instructor if you have booked a DECO/TRIMIX course for the MKVI.

This NEW battery Unit which contains one of the 4 Microprocessors on a MKVI Rebreather contains updated Firmware, please see notes below, please note the below Update relates to both the 40m DECO and 48m Trimix Updates. 

Decompression Firmware Update - Diver's Release Notes

Hardware update, 40m deco Air or 48m deco Trimix. The update will be distributed through a color coded battery.

The MK6 now has support for decompression diving. To do decompression diving, two parameters need to be set.

  • 'Decompression permitted'. This can only be set by Poseidon. Only users that have the requisite credentials will have the 'Decompression permitted' parameter set.
  • 'Decompression enabled'. This can be set / cleared by the user. If 'Decompression permitted' is not set, then this parameter is meaningless.

If both 'Decompression permitted' and 'Decompression enabled' are set, then the MK6 is configured for decompression diving. It is possible to tell that a rig is configured for decompression diving by examining the ceiling indicator during pre-dive. The ceiling indicator will be blank for a standard rig and will flash for a decompression rig.

During predive, the diver will be asked to confirm the Helium fraction in the diluent if either the rig is configured for decompression diving or the configured diluent is not air. This test occurs immediately after the Mouthpiece CC test. The rig will display 'HE' 'Fr' 'nn' in succession in the PO2 field, where 'nn' is the assumed helium fraction in the diluent. The diver will have to acknowledge this by going through the standard wet / dry sequence. If the helium fraction is wrong, then the diver can either:
Use the IrDA link to change it to the correct value. The new value will appear in the LCD.
Let the test timeout (two minutes) at which point the rig will shut down.

A decompression rig will exhibit different behavior as the diver approaches and enters decompression.

  • The ceiling indicator will not flash. Rather it will just be lit.
  • The ceiling indicator on will not cause the Alert triangle to be on.
  • The rig will not issue an alarm (LED, vibrator etc) when decompression is entered.
  • Decompression related issues (as opposed to alarms) will be signaled via a new tone sequence on the battery, and a new vibrator sequence on the HUD.

A decompression rig has a different controlling resource algorithm (CRA). In a standard rig, the remaining dive time is the minimum of remaining dive time (RNDT), Oxygen supply, Battery supply, OTUs. What this means in practice for most divers on most dives is that the remaining dive time is the RNDT. 
For a decompression rig, an RNDT of zero is permissible and will not generate an alarm. Thus the CRA instead reports the remaining dive time as the minimum of Oxygen Supply - TTS, Battery Supply -TTS, OTUs - TTS. The controlling resource will be reported as whichever resource is the least (normally oxygen). However if the TTS exceeds 125% of any of Oxygen supply, Battery supply, OTUs, then the CRA will report the controlling resource as decompression.

A decompression rig uses a different PO2 setpoint algorithm. The intent of the algorithm is to keep the setpoint higher for longer. This comes at the cost of making buoyancy control harder in shallow water (which should not be a problem for an experienced diver). The algorithm is to always use the highest setpoint (typically 1.3 bar), subject to the following limitations:

  • The FO2 is limited to 85%. Thus at the surface the setpoint would be 0.85 bar. At 3m the setpoint would be 1.105, and at 6m and greater the setpoint would be 1.3 bar (for a rig with a 1.3 upper setpoint).
  • The hyperoxic linearity test still applies. Thus a rig that fails the hyperoxic linearity test will not be allowed to use a setpoint > 1 bar.

The rig also now supports a maximum TTS (Total Time to Surface) parameter. The maximum TTS is set. If the TTS exceeds the maximum allowed TTS, then an alarm response similar to exceeding the maximum working depth of the rig will be generated.

The rig now supports an IrDA command 'power up'. The latest PC SW should support this feature. To use it, simply wet the wet switch and then connect the IrDA link. The PC will then force the rig to power up without having to go through the wet switch wet / dry / wet exercise.

The Mk6 will only accept Normoxic diluent mixes in both updates. Helium fraction is without limitation.


Additional Information

Additional Information

Manufacturer Poseidon
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Customer Reviews 1 item(s)

Worth the upgrade
Am only just starting to use the DECO features on this upgrade but already finding it very useful, But No point unless you want to do DECO dives to 30-40m ish. You do need to turn it on using your PC/Laptop as it works like a standard Battery until turned on. and you can only have one if you are qualified or under training. - TAL Review by Trevor / (Posted on 13/10/2012)

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