Duracell 9V alkaline Ultra vs. Plus battery test

Description:

We have just finished building our new IR datalink USB which is 9 Volt battery powered. We decided to implement a battery gauge in the new IR datalink, so it is possible to predict how much battery life you have left based on the current battery voltage. We then discharged two different model Duracell 9 Volt batteries to gather data for our prediction. We placed the test battery in our IR datalink which uses approx. 60 mA, turned on power and measured the voltage during the discharge of the battery till is was empty at 5,6-5,7 Volt.

So is it a good economy to buy the more expensive Duracell Ultra (5,25 € in Denmark 08/2009) vs. the cheaper Duracell Plus (4 € in Denmark 08/2009)?

Take a look at the graph below showing battery voltage during discharge with our IR datalink.
As you will see the Ultra battery is only approx. 13% better than the Plus battery, but 25% more expensive in Denmark!

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