Batteries and Dive Computers
I'm going on a diving trip soon, so last weekend was spent testing and packing gear. While testing the dive computers we discovered that my computer had lost some battery charge; not enough to cause any immediate problems, but I don't really want to find myself with a 'low battery' warning out at sea. It's not surprising that the battery has lost some charge, I've done a lot of diving with this computer, and the battery is holding up very well compared to the expected lifespans listed in the manual. Since the idea of changing batteries part-way through the trip was not appealing, part of my pre-dive work was to change the battery on land.

The recommended way to change the battery on this model of dive computer is to purchase a 'battery kit'. This includes a new CR2032 lithium battery (valued at $4.00), a new O-ring (valued at $0.05) and a new plastic battery cover (valued between $15.95 and $45.95, depending where you buy it from). The battery kit is a good idea, it ensures that you're not reusing worn, damaged, or dirty parts.

Unfortunately, finding a battery kit proved to be difficult, and I wanted my battery changed before I went away. Given this is the very first battery change, and that I have silicon grease and lint-free cloths at hand, I decided to just purchase the replacement battery, which are cheap and easy to find. What was interesting is some of the discussions I had with equipment technicians regarding dive computer design.

It appears that most dive computers have their actual electronics embedded in what's informally known as "potting mix". This is a waterproof gel which means that even if water does enter the computer case then it's unlikely to cause immediate failure. In fact, the most likely problem to be caused by water leakage is corrosion of the battery contacts. While that's a bad thing, it's a lot less dangerous or expensive than total computer failure. There's even a possibility that the computer can partially self-diagnose; the corrosion reduces voltage available from the battery and results in a low-battery warning.

The net result is that I need feel much better and safer with my newly replaced computer battery, instead of being concerned about damaging seals during the replacement and having to use a bottom-timer and tables during my holidays.