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Matthew:
I was part of an expedition up to the arctic ice to collect gelatinous zooplankton. We took six pre-production Edges with us to use, this was the first use of dive computers from a National Science Foundation vessel.
As usual we planned Bingo air (with appropriate alterations for blue-water diving) which includes planning for possible decompression in case we overshot our plans by one depth and/or one time bracket.
The first two dives were uneventful, the Edges worked fine and everyone was cold limited rather than decompression status limited (for a change). The dives were in water that was about -1 degree C for about an hour with maximum depth excursions down to 60 FSW.
On the third dive, one that we planned to 100 FSW, all six computers failed during the dive, not everyone was wearing a backup timer or watch, but we knew the depth because of the blue-water rig which limited our descent. So we ascended to twenty feet and worked there until we hit our Bingo air at which time we came up to ten FSW, took five minutes there and surfaced.
The computer problem was one that we had not considered (neither had the manufacturer), due to the remote nature of the cruise, and the way in which these early computers ate batteries, we had decided to use rechargeable batteries rather than ballasting the ship with alkalines. These nicads have a very different discharge curve and on the third dive they were low enough to blow right through the low battery warning in a matter of minutes as they chilled. We solve the problem by rotating dive crews (making sure that those that had lost their data were out of the water for 18 hrs.) and always starting each dive with a freshly charged battery. There were no further incidents
