“Battery Technologies”
Photo from depositphotos.com: A pile of used batteries.
By Scott Hamilton
The technology of batteries is something that has always both fascinated and annoyed me over years of study. I studied battery technologies as a project in college to determine if there were any differences in performance between battery brands, or if it was all marketing. It’s been a lot of years since that study, but I still recommend Duracell batteries for anything dealing with radio signals. It’s a little hard to explain, but it has a lot to do with how “clean” the energy is that comes out of the battery. At the time of my study Radio Shack was still a store that you could go into and buy just about anything for an electronics project, including some really cheap batteries. Price wise I would put the Radio Shack batteries right there in the same price ranges as Dollar Tree batteries. Surprisingly, these cheap batteries from Radio Shack provided more energy than the much more expensive batteries, but their power was not clean. They worked great for running electric toys, like RC cars, battery operated trains and were the best in flashlights, but they were horrible for wireless microphones and walkie-talkies.
I will try to explain the reason as best I can without getting too technical. Batteries are designed to power direct current circuitry, whereas the power coming from your electrical outlet is alternating current. The difference between the two is that alternating current cycles between a positive and negative voltage at a certain frequency. In the United States the standard is from -60 volts to +60 volts, 60 times a second. Direct current means that the voltage stays at a constant level all the time, for example the standard AAA battery in your TV remote operates at 1.5 volts. The difference between the cheapest battery (Radio Shack) and the most expensive battery (Duracell) in 1992 was not only a significant price difference of almost four times, but a difference in quality. The Radio Shack battery held a voltage above 1.2 volts under load for four hours, and the Duracell did the same, but only three hours and forty five minutes. You might think at first that the Radio Shack battery was better, but as soon as you look at the voltage of each battery over time with an oscilloscope, you get a very different picture.
An oscilloscope is an instrument that displays a picture of a voltage signal on a screen; it plots the change in the voltage over time. The Radio Shack batteries displayed a voltage that oscillated, or changed voltages at a regular interval. The voltage shifted from around 1.7 volts to 1.3 volts at a fairly constant rate around 650 times a second. The Duracell battery, on the other hand, showed no change in voltage until it began going dead, it then showed a steady drop over about five minutes, from 1.5 volts to 1.2 volts, at which point in my testing I considered the batteries to be dead.
The most interesting thing about this experiment was that the oscillation of the Radio Shack batteries landed right in the middle of the standard frequency range on wireless microphones. When we used Radio Shack batteries in wireless microphones, we had issues with a constant hum and more problems with feedback. When we used the more expensive Duracell batteries, we had fewer problems with the wireless microphones overall. I did not know why until the experiment in college. As it happens, the cheaper batteries were causing radio interference in the microphone because they were oscillating at the same frequency as the crystals in the microphones.
This problem of quality control in the battery industry is only one example of the things that frustrate me about batteries. This problem may have gone away in recent years, and I should repeat the study some day, especially since we have brand new technologies in today’s batteries. I still recommend Duracell batteries in critical equipment, but no longer have any significant reason for the recommendation without repeating the tests. As it appears that I have gone on too long reminiscing in the first point, I shall have to continue the story next week with a second thing that I find disturbing when it comes to battery technologies. Until next week, stay safe and learn something new.
Scott Hamilton is an Expert in Emerging Technologies at ATOS and can be reached with questions and comments via email to sh*******@te**********.org or through his website at https://www.techshepherd.org.
