I have this nifty little thing called a Rio, which stores MP3s on it(you plug it into the computer and upload stuph). On the little display, it tells you various info, such as what track you’re on, or whatever.

Anyway, one of the little things shows how much battery power is left in. I noticed while I had a duracell in, it drained like most batteries should. But when I plopped in an energizer battery- Interesting stuff occured. The battery drained reeeeal slow, and if you left the machine off for long enough(several hours), the display would tell you the batteries had as much juice in 'em as when they STARTED. Due to this, the battery lasted 2 months.

now, I’m wondering. I think energizer has done this before in other things, but I can’t be for certain(they don’t have battery power displays). Does anyone know whether it’s the Energizer battery itself(the bunny alone tells you it’s better than duracell), or the piece of equipment? (Diamond Rio)

-Th’ JawaTrader

It’s both. Different batteries respond differently to different loads, and if battery A lasts longer than battery B on something that takes a lot of power, it is still entirely possible that battery B will last longer than battery A on something that just takes a little.

To some degree, battery formulation comes under the heading of black arts.

John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams

Different batteries have different discharge curves, even if they both totally die at the same time. Alkaline batteries tend to have a flat discharge curve, falling off dramatically towards the end of their lives, while carbon-zinc batteries will show a gradual dropoff in voltage right from the start. (Actually, both batteries will, but the Alkalines won’t drop off as much).

It’s also possible that the Duracell battery you had in there had been on the shelf for a long time before you used it.

You know, that begs another question:

About every year or so, someone somewhere puts out a press release claiming a “dramatic breakthrough” in battery technology. And about every five years or so, battery companies release a New and Improved* product that dramatically outperforms those paperweights you just blew all your money on.

So with all that progress out there, why am I still plugging things into the damned wall? Anyone care to comment on the progress of battery technology today as compared with your Cold War vintage Boy Scout flashlight operating times?

Three things are going on here. Batteries have a total capacity, discharge rate and internal resistance. Energizers and Duracell Ultras have greater capacities and discharge rates than carbon zinc and cheap alkalines. Total capacity obviously means longer use. Discharge rates can be noticed in flashes on cameras. The battery with a faster discharge rate will have more flashes in a period of time than one with a slower discharge rate. Lithium and nicad batteries have less internal resistance than alkalines. It is related to discharge rate. When you use a battery in a flashlight it heats up and causes more internal resistance. When it cools down the internal resistance goes down and therefore appears to have more power or capacity.

Nicads have the flattest discharge curve followed by lithiums, alkalines and carbon zinc. I don’t know where lead acid or nimh batteries fits in there.

The main progress has been a much higher price. And Eveready, who has made flashlights for about 100 yr, has learned how to make them acquire poor contact in a very much shorter time. I recall when a D cell cost about 10¢. Better living through electrochemistry (for electrochemists).