Tabbykatt3:
I received the following warning from Cochran when they were servicing my Gemini Plus which I thought may be worth passing along:
"You will ship out today. And please, we recommend not using the Energizer Lithium batteries in these computers. Althought they are a very good battery, the voltage is much more than the 1.5V we recommend for our computers. Thanks Kurt and Happy Diving!!"
First let me state clearly that I am not a battery expert.
I have not noticed that lithium batteries have a significantly higher voltage than alkaline batteries, but a slight difference might be an issue.
I have read elsewhere that lithium batteries maintain a relatively flat voltage for their service life, but when they die, they die very quickly. This will fool your computer into reporting voltages that still indicate that the battery is still relatively good, until the floor falls out.
A normal alkaline battery has a relatively "normal" voltage drop as the battery is consumed. In short, when an alkaline battery dies you can see it coming.
An example of this is best seen in a flashlight. With a normal alkaline battery as the batteries wear down the bulb will begin, slowly over time, to brown out. The same light with lithium batteries will stay relatively bright for almost the entire life of the batteries, until over the course just of a few minutes, as the batteries die, the lamp begins to brown out and finally die.
This is not limited to Cochran computers, or frankly any dive computers. This is typical of any electronic device that is utilizing a lythium battery. When the remote for your TV dies abruptly it is not that big a deal. When your dive computer croaks, you might have a problem.
Lithium batteries have a great shelf life, which is why they might be a good choice for the TV remote, you know, used only a short time each day, but sitting there ready for use for months or years. Your Cochran Gemini tank unit is running all of the time, so the end of the batteries life is an unwelcome surprise.
I change the batteries in my Gemini once a year or so, and before an extended string of dives, or particularly cold dives.
Mark Vlahos
