Bests & Worsts Reviews from Amazon

I have just compared the product data sheets for the Duracell Coppertop MN1300 and the Procell by Duracell PC1300. These are both 1.5-volt, D-size, Alkaline-Managanese Dioxide batteries made by the same manufacturer. They have similar overall operating characteristics, but THEY ARE NOT THE SAME. Before getting into the details, I'll give you the bottom line: Under cold conditions, the Procell will probably perform considerably longer, maybe as much as 50% longer. At room temperature, the Duracell should perform somewhat longer, perhaps 16% longer. But be warned that these numbers depend on a lot of variables. To know how they'll work for you, you've got to look carefully at the application. WHAT DETERMINES BATTERY LIFE These products have been tested under controlled laboratory conditions, and the results are shown in the charts included in the manufacturers data sheets. If you don't spend the time to read beyond the overview chart at the top, you may conclude that the batteries are identical. They are not. Rather, as the spec sheets warn us in red ink: “Delivered capacity is dependent on the applied load, operating temperature and cut-off voltage.” Now, most users do not know their applied load, and they may or may not know the temperature and cut-off voltage they are looking for. Yet, these factors can have a very large effect on performance, and weigh heavily on which is the right battery type for you. AN EXAMPLE THAT FAVORS PROCELL Let me try to make this clearer by describing an application that I have for the D-cell batteries. I use four of these in a battery-powered ozonator that my wife likes to keep in the refrigerator to reduce odors. Although I have a fairly good idea of the operating temperature. I do not know the current drain. I know from experience that when the ozonator starts flashing red, indicating a low-battery condition, the batteries test at about 1 volt. If I examine the charts for a constant current drain of 250 mA (milliamps}, the fall-off to 1 volt occurs at approximately 46 hours for the Coppertop. The fall-off to 1 volt for the Procell occurs at approximately 43 hours. So there is a difference, amounting to about a 7% longer life for the Coppertop. As my batteries seem to last about 3 months (2,160 hours) in this application, I assume that either the current drain is much less than 250 mA and/or that the device cycles on and off, so the drain is not constant. There is no chart for this, so it remains an assumption that the Coppertops might last longer under my operating conditions. And I can add that my “gut feeling,” after changing to the Procells for two operating cycles, was that the Coppertops were probably outlasting them. However, another comparison of charts, those showing the service hours at constant temperature at 250 mA, gives the advantage to the Procell. My refrigerator is kept at 37ºF (2.8ºC), so the charts for performance at 0ºC are fairly applicable. At this temperature, the fall-off to 1 volt for the Coppertop occurs at approximately 16 hours. For the Procell it occurs at about 24 hours. This is a huge advantage for the Procell, amounting to 50% longer life! This might explain the experience of reviewer D. McLauglin (“Solid Product!” on August 10, 2011) who compared the performance of the Coppertops to the Procells in two identical trail cameras, and found that the Procells outlasted the Coppertops by 4 weeks in a test of several months duration. McLauglin did not keep a continuous recording of temperature, but he says that the cameras sat through snowstorms as well as rising and falling temperatures. If he had used them under summer conditions, he might have found different results. He also didn't try a second test in which the cameras were exchanged, in order to eliminate the possibility that one device drew more current than the other. But he is certainly to be praised for running a months-long test, and a far more scientific one than I have yet tried. A DIFFERENT EXAMPLE THAT FAVORS COPPERTOP But don't jump to the conclusion that the Procell will give you a longer service life if you are planning to use it at room temperatures. When compared at room temperature (21ºC/70ºF), the Coppertop has the advantage—about 46 service hours, compared to 43 hours for the Procell to reach the 1 volt level. And if your application allows you to drain the battery down to 0.8 volts, the Coppertop has a little further advantage, reaching 0.8 volts after 50 hours, while the Procell has drained to 0.8 volts in 43 hours. That gives a 16% advantage in service life to the Coppertop. But remember that these are the service hours for continuous current drain at 250 mA. What if your current drain is different. And what if, as often happens, it is intermittent and not continuous? Does it get better or worse for the Coppertop? We don't know. . . . AND THE PRICE CONSIDERATION So you see, it is not possible to give a one-size-fits-all answer to the question of which battery is better. And of course, price must be taken into account. Presently, the best deal I can find on Amazon for the Coppertop D battery is in an 8- pack for $16.19, or $2.02/count, with free (but not Prime) shipping. The Procell D battery comes in a 12-pack for $14.48 or $1.21/count (with Prime shipping). This gives a vast price advantage to the Procell in the Size D battery. And for many uses the Procell will prove equal or superior to the Coppertop. But for some applications, the longevity advantage will go to the Coppertop, and if more frequent changing of the battery is an issue, that might be the better choice. To sum it all up: Despite my “gut feeling” about the Coppertop advantage in my refrigerator application, my research now suggests that the Procell D battery is not only much cheaper, but probably considerably longer lasting for this specific application. For use at room temperature, the Coppertop will have a slight advantage, but after price is taken into account, the scale still leans toward Procell. REFERENCES: Spec sheets used for this analysis are MN13CTUS0413 for the Coppertop, and PC13US1214 for the Procell.