Incident due to battery change on dive computer

[Bert van den Berg]

After changing the battery on my dive computer I had to reset the date/time and units of measure but forgot to change the Personal Safety Factor to "Medium" (the default is Personal Safety Factor 2). Did a wreck dive to a maximum of 93 feet (70 feet average for 46 minutes) that was identical to one done in December without issue. The dive computer decided that I went into deco and demanded a stop at 39 feet for 2 minutes (did that) and another at 10 feet for 31 minutes. I realized at that point what happened and only did three minutes at 15 feet. This was the first time ever that the computer told me I was in deco so had no prior experience. With Personal Safety Factor 2 the bottom time is roughly cut in half. A look at the PADI dive table said we were at the limit but not into deco with 70 feet/46 minutes.

Did a second dive 1-3/4 hours later to find that my dive computer refused to compute/display deco time because I had violated my deco on the earlier dive and it was only providing depth, bottom time and temperature. Since I was buddied with a Dive Master and understood what happened and since the buddy and I were glued together on the first dive I thought I would just rely on his computer. 20 minutes into the second dive I looked at his computer to discover that it was displaying the word "UP" instead of time remaining till deco.

I called the dive and we ascended from 80 feet taking 19 minutes to do so with a five minute stop at 15 feet. The dive tables said that we probably went into deco on the second dive and should not have spend more than 10-15 minutes there. I was not happy with my decision to dive without a properly working computer and also very unhappy to find that a Dive Master certified diver would do the same. Lost quite a bit of sleep that night and decided that was never going to happen again.

 

[KenGordon]

After changing the battery on my dive computer I had to reset the date/time and units of measure but forgot to change the Personal Safety Factor to "Medium" (the default is Personal Safety Factor 2). Did a wreck dive to a maximum of 93 feet (70 feet average for 46 minutes) that was identical to one done in December without issue. The dive computer decided that I went into deco and demanded a stop at 39 feet for 2 minutes (did that) and another at 10 feet for 31 minutes. I realized at that point what happened and only did three minutes at 15 feet. This was the first time ever that the computer told me I was in deco so had no prior experience. With Personal Safety Factor 2 the bottom time is roughly cut in half. A look at the PADI dive table said we were at the limit but not into deco with 70 feet/46 minutes.

Did a second dive 1-3/4 hours later to find that my dive computer refused to compute/display deco time because I had violated my deco on the earlier dive and it was only providing depth, bottom time and temperature. Since I was buddied with a Dive Master and understood what happened and since the buddy and I were glued together on the first dive I thought I would just rely on his computer. 20 minutes into the second dive I looked at his computer to discover that it was displaying the word "UP" instead of time remaining till deco.

I called the dive and we ascended from 80 feet taking 19 minutes to do so with a five minute stop at 15 feet. The dive tables said that we probably went into deco on the second dive and should not have spend more than 10-15 minutes there. I was not happy with my decision to dive without a properly working computer and also very unhappy to find that a Dive Master certified diver would do the same. Lost quite a bit of sleep that night and decided that was never going to happen again.

Oops. Try not to do that agin. If that was today, take tomorrow off. I think you were quite likely properly in deco and not suffering from a just an incorrectly set computer. It depends on the profile. For a wreck I'd guess that's squarish.

I would not assume a 'Dive Master' is qualified to do deco dives or has a better understanding of the algorithms, tables and computers than you do. He is likely to be younger, fitter and more dived up than you though.

Unless you are at real risk of running out of gas or getting so cold as to be a problem then I would prefer sitting out the stops in such circumstances.

When you looked at the tables did you read them for 70 (the average) or 93 (the maximum)? By my tables both those for a 46 minute dive are into stops. The correct depth is 93ft properly into deco - 1 at 9m and 6 at 6m which is a lot on BSAC88 tables which are not known as conservative (also assuming you arrived a 9 at 46 min, not left the bottom at 46min.

I won't tell you how much deco you skipped for 30/70GF which my petrel defaults to as it might scare you.

Read deco for divers, understand what drives deco obligations and how the algorithms vaguely work.

Dive nitrox for these depths.

Do not go on someone else's computer except in case of actual failure of your own. Two people on the same dive should go with the more conservative computer.

Try planning dives a bit. Then you have some idea when you get in the water how long you can be and how much gas you will need. It is embarrassing to discover you have 31minutes of stops when you only have gas for 10.

You might want to try a simulated deco dive. Dive 32% but set one computer to air and your buddy's to 32%. Do a dive planned between the nitrox and air NDL but follow the air computer. Or do it all on tables but chose a much reduced bottom time.

Being committed to stops is something you need to get your head around when it does not matter. When you are cold, need to take a leak and having a hard time with buoyancy because you are low on gas is not the time to discover that your head isn't up for it.

Ken

 

[Rich Keller]

I will never understand why you people trust your lives to the quality of a computer or even worse a battery. You were trained to use tables and forgot everything you knew as soon as you got a computer. If you had a clue and a waterproof dive table this would never have been a problem. Instead you push as close to the limits as you can and when something goes wrong you blame the DM! You ignored a very basic part of your training for the sake of convenience and a few extra minutes of bottom time. You are ultimately the only one responsible for your own safety. Try one of these, it never fails and will cost less then your batteries.

Aqua Water Proof Dive Tables 6" X 8" (15.2 cm x 20.3 cm) SL11

 

[Basking Ridge Diver]

Echo what the others have said - I generally look at the tables to understand the dive and what is expected so I have an idea of how long and how deep (Plan the Dive) but I dive my computer knowing in my mind what the numbers are (Dive the Plan) and what my consumption rate is for this dive (RMV). Trust my computer but I verify the computer numbers and what it is telling me before it tells me I died...

I am glad you are ok - I hope you and your buddy learned a valuable lesson.
That said - it is surprising that given the number of dives on your profile you are not following some type of plan other than I did this before... Complacency or poor planning?
Stay safe.

 

[victorzamora]

After changing the battery on my dive computer I had to reset the date/time and units of measure but forgot to change the Personal Safety Factor to "Medium" (the default is Personal Safety Factor 2). Did a wreck dive to a maximum of 93 feet (70 feet average for 46 minutes) that was identical to one done in December without issue. The dive computer decided that I went into deco and demanded a stop at 39 feet for 2 minutes (did that) and another at 10 feet for 31 minutes. I realized at that point what happened and only did three minutes at 15 feet. This was the first time ever that the computer told me I was in deco so had no prior experience. With Personal Safety Factor 2 the bottom time is roughly cut in half. A look at the PADI dive table said we were at the limit but not into deco with 70 feet/46 minutes.

Did a second dive 1-3/4 hours later to find that my dive computer refused to compute/display deco time because I had violated my deco on the earlier dive and it was only providing depth, bottom time and temperature. Since I was buddied with a Dive Master and understood what happened and since the buddy and I were glued together on the first dive I thought I would just rely on his computer. 20 minutes into the second dive I looked at his computer to discover that it was displaying the word "UP" instead of time remaining till deco.

I called the dive and we ascended from 80 feet taking 19 minutes to do so with a five minute stop at 15 feet. The dive tables said that we probably went into deco on the second dive and should not have spend more than 10-15 minutes there. I was not happy with my decision to dive without a properly working computer and also very unhappy to find that a Dive Master certified diver would do the same. Lost quite a bit of sleep that night and decided that was never going to happen again.

Using my algorithm, assuming air, and assuming your 70ft average is accurate (I'm actually guessing your average was deeper for the "bottom portion" of the dive).....I'm showing 20 minutes of deco that you missed. At 75ft, you missed about half an hour of deco. At 93ft, you missed 51 minutes of deco. Even running a known-liberal algorithm, you're still talking about 20min of missed deco at 75ft "real" average.

Diving with a locked-out computer is also super scary, as you had no way of calculating your actual deco status. Had you have whipped out tables, there'd be no issue. Next time, pay better attention to your computer and follow your stops if you do go into deco.

 

[Colliam7]

Did a wreck dive to a maximum of 93 feet (70 feet average for 46 minutes) that was identical to one done in December without issue. The dive computer decided that I went into deco and demanded a stop at 39 feet for 2 minutes (did that) and another at 10 feet for 31 minutes. I realized at that point what happened and only did three minutes at 15 feet. This was the first time ever that the computer told me I was in deco so had no prior experience. With Personal Safety Factor 2 the bottom time is roughly cut in half. A look at the PADI dive table said we were at the limit but not into deco with 70 feet/46 minutes.

Did a second dive 1-3/4 hours later to find that my dive computer refused to compute/display deco time because I had violated my deco on the earlier dive and it was only providing depth, bottom time and temperature. Since I was buddied with a Dive Master and understood what happened and since the buddy and I were glued together on the first dive I thought I would just rely on his computer. 20 minutes into the second dive I looked at his computer to discover that it was displaying the word "UP" instead of time remaining till deco. . . . I was not happy with my decision to dive without a properly working computer and also very unhappy to find that a Dive Master certified diver would do the same. Lost quite a bit of sleep that night and decided that was never going to happen again.

I applaud you for posting your experience! I suspect that this situation occurs more often than we hear about, but only a few divers, such as yourself, a) realize what has happened, b) analyze what they did, and c) share it with others as a 'lesson learned'.

I attended a DAN Safety Seminar last week, where several of the points made were relevant to this type of situation: a) there is essentially never an 'undeserved hit', b) many of us dive without really knowing what calculations our computers (or deco software for that matter) are performing (even if we know the 'model' being used, the code is frequently not open source), and c) just because we have done a particular dive before without incident, there is no guarantee we can 'get away with it' again. Good food for thought, and your experience amplifies the importance of such a message. Thank you..

 

[rhwestfall]

Sounds like you have been playing Russian Roulette all along, and this time tried it with 5 of 6 chambers in the cylinder loaded. Somehow, you were lucky.....

I'd seriously think about stepping back, and re-learning some dive planning.....

Rather luckily, you rather than Dandy Don posted this....

 

[Hawkwood]

... Did a wreck dive to a maximum of 93 feet (70 feet average for 46 minutes) that was identical to one done in December without issue. ... A look at the PADI dive table said we were at the limit but not into deco with 70 feet/46 minutes. .

No, the RDP uses maximum depth, not "average" depth. You exceeded the RDP's NDL for a dive to 93 feet of 20 minutes. You can't use the RDP in that fashion.

 

[SubAquatix]

I attended a DAN Safety Seminar last week, where several of the points made were relevant to this type of situation: a) there is essentially never an 'undeserved hit', b) many of us dive without really knowing what calculations our computers (or deco software for that matter) are performing (even if we know the 'model' being used, the code is frequently not open source), and c) just because we have done a particular dive before without incident, there is no guarantee we can 'get away with it' again. Good food for thought, and your experience amplifies the importance of such a message. Thank you..

You know, you can love or hate DAN, but the Monthly Seminars are always interesting!!! Missed the first, sadly, since a new club was starting in town, but Dr. P had some great info in his presentation!!!

 

[stuartv]

You were trained to use tables and forgot everything you knew as soon as you got a computer.

Not necessarily. SDI OW doesn't teach tables (unless the instructor chooses to go above and beyond the standards) and PADI OW also has that option as well now.