Power Struggle

The most quietly innovative thing that emerged from the latter half of the ’90s was the on-battery power meter. It was the subject of a complex patent battle.

By Ernie Smith

Today in Tedium: The world has changed immeasurably in the years since the battery wars of the 1980s and 1990s—a time when seemingly every gadget had a corresponding need for incredibly valuable, but somewhat wasteful, alkaline batteries. These days, of course, batteries are still with us, but they tend to be rechargeable and possibly embedded in our devices, so we’re not throwing away batteries every time we use a device for a few hours. But near the end of the 20th century, our need for batteries knew no bounds. There was just one problem, and that problem was … the average person had no idea if a battery was going to work or not if it was just in a drawer—until one day in the mid-1990s, when the two largest battery manufacturers decided to release a measurement system that lived inside of the battery. It seemed like magic, even if it was really basic electronics at play. And despite announcing the technology at the same time, it was very much not in tandem. Today’s Tedium talks about the simple novelty of on-battery power meters—and the legal battle the competing options inspired. — Ernie @ Tedium

Thanks to Nick Dimichino for inspiring me to write about this.

Tedium on Patreon

Keep Us Moving! Tedium takes a lot of time to work on and snark wise about. If you want to help us out, we have a Patreon page where you can donate. Keep the issues coming!

We accept advertising, too! Check out this page to learn more.


The year that a group of representatives in the U.S. federal government, the battery industry, and heavy users of batteries got together to decide on a standardized measure for battery sizes. Ultimately, the alphabet system came into effect, though many of the battery sizes decided on at that time did not come into common use—particularly A and B batteries—in part because battery technology was improving by leaps and bounds, making room for alternatives such as AA, AAA, and (more recently) AAAA. Despite the retirement of some sizes, others maintain an unusual foothold in the modern world.

Energizer Battery Tester

Energizer’s take on the on-battery power meter. (via YouTube)

How the heck does an on-battery power meter work, anyway?

It may be the most ingenious, yet unheralded invention of the late-20th century: A battery that had a built-in meter to tell those buying the batteries just how much of a charge the device had.

You could grab a battery out of a junk drawer, measure the amount, and then decide you could move forward with your Game Gear game—after, of course, you found five more working batteries. It saves you the pain of putting batteries in, say, a flashlight and confirming they work the hard way.

That was the world Duracell and Energizer promised us when they released their on-battery testers in the late 1990s. You might be wondering, how did they do that?!?

The short version: By wasting a little bit of your energy, with the help of a clever use of heat-sensitive ink.

Now, let’s break that down a bit.

A key element of the meter is that you basically are expelling a little bit of energy each time you use it to highlight the level of charge. If it ran constantly, it would effectively drain the battery just as quickly as it might if it was plugged in while doing something useful.

But by expelling the battery in short bursts, it offers a useful way for a battery user to track how much capacity it can let out. The larger the capacity, the longer the use time.

Another key element of this process, as highlighted by the YouTube channel “xofunkox-scientific experiments,” involves the thermochromism, or a process in which an object changes color thanks to the addition of heat. (If you’ve ever used a mood ring, same concept.) The channel was able to recreate the effect of the Duracell PowerCheck by painting a piece of brass foil with thermochromic ink.

Now compare that to the process the Duracell PowerCheck went through as you charged it. As more energy flows through the foil, the paint on the foil changes color, just like the meter on the battery.

This is effectively an analog way of confirming that a battery has enough juice. There are other, more detailed ways to track the power level inside of a battery by measuring the battery’s ability to sustain a charge, using a device such as a multimeter.

But for the average person, this approach was simply too complicated. A great way to think about this is in terms of wireless connection. If you set up a WiFi connection in your home, you can learn all sorts of things about it using the right application. But the average person just wants to know the password so they can get online. They don’t have time to worry about things like signal strength … even if they might be affected by those problems. Heck, even people who do care might just want to get the problem out of their way.

So just saying that a battery level is “good,” as Energizer batteries did, was a great way to simplify things for the average person, while letting battery die-hards benefit from additional technical knowledge through other means.

So that’s how an on-battery meter works. But there’s a story about how it came to life that deserves a discussion—a mess of patents that competed with one another to sell the same idea to the same impressed public at the same time.

“If the battery seems reasonably clean, stick it to your tongue. You will feel a slight jolt and metallic taste. You’ll probably need to calibrate your tongue by testing a fresh battery and a dead battery to get an idea of what to expect.”

Amanda Ghassaei, a engineer and researcher, in a guide for Instructables that describes how to measure the charge level of a nine-volt battery by sticking it against your tongue. As such batteries have both connectors on the same side, you can feel the positive and negative effects coming together all at once.

Patent Battery Drawing

Drawings from a patent filed by James R. Burroughs and Alan N. O’Kain that explain the battery-testing technology. (Google Patents)

The complicated patent battle that charged up the on-battery power meter debate

Something strange happened on December 14, 1995: Both of the major national battery brands, Duracell and Energizer, announced that they were adding this innovative power-testing technology to their respective battery lines. In the case of both companies, it was a significant upgrade—while Duracell had a useful tester inside its plastic case, while Energizer maker Eveready sold its model separately.

But there was just one problem with the announcement: only one of the companies had legally licensed the technology that made this innovation possible. What happened?

Both were working on releasing the technology: Energizer announced first, and as soon as Duracell found out, it released a press release of its own, essentially to show Eveready that it, too, had the goods.

But why did both companies have the goods? Well basically, the U.S. Patent and Trademark Office approved patents for two separate battery-charging technologies during roughly the same period. And, unwittingly, USPTO set up a David vs. Goliath story of a patent battle.

In one corner was Eastman Kodak, still a giant of innovation at the time with a massive camera business to support itself; in the other, an independent inventor team that came up with the idea on a hunting trip, when a flashlight konked out. And at the center, a patent system that has faced challenges of increasing complexity in recent years, and accidentally approved the same general idea twice.

This was not a fight that favors the inventor working alone. Despite the fact that said inventor, James R. Burroughs, filed first with his business partner Alan N. O’Kain, they were by far the smaller of the two organizations—essentially a pair of entrepreneurs taking on both an iconic camera company and an iconic battery company—and it meant that it would potentially be easy to wear the patent-filers down through legal action.

In the patent filing by Burroughs and O’Kain, it’s made somewhat clear by the that the device was clearly inspired by personal frustration with testing batteries manually:

Most individuals test their batteries by turning on the device in which the batteries are installed. If the device operates, the individual is normally satisfied that the batteries are operational. Some individuals will test the batteries on a battery tester to determine the condition of the batteries. Some individuals will even test the batteries under both loaded and unloaded conditions to measure the voltage drop. Although it is not complicated to test batteries, it is time consuming to disassemble a device, remove the batteries, test the batteries, and, if they pass the test, reinstall the batteries in the device. It is normally not possible to test new batteries at the time of purchase because of the battery protective packaging.

Accordingly, it is the object of the present invention to provide an improved battery having a built-in battery-strength indicator which permits one to immediately determine the battery’s strength or condition. Thus, with the improved battery of the present invention, a user can quickly and effortlessly determine the strength or condition of a battery. When a battery is easily tested, as the battery of the present invention, the user of the battery is more likely to routinely check condition of the battery.

(That said, they had also considered the problem from the other angle, creating a flashlight that added more robust battery-testing capabilities.)

Kodak Patent Battery Drawing

A drawing from the Kodak patent for the on-battery power meter. (via Google Patents)

The Kodak patent, which was initially filed about a year after Burroughs and O’Kain filed theirs and granted six months after the Burroughs patent, has a design very similar to what ended up in the Duracell PowerCheck. (Which makes sense, because it’s the version Duracell licensed.)

It, meanwhile, noted that many external battery testers were already on the market but by their nature inconvenient—including in the case of the in-package testers of the kind Duracell was known for:

These testers generally include a conductive layer in thermal contact with a temperature sensitive color indicator layer. When the ends of the conductive layer are contacted to battery terminals, electrical current flows, creating heat in the conductive layer. The heat causes a change in the indicator layer.

The usefulness of the above devices is extremely limited. They are also inconvenient to use. The tester must be carried as a separate item. This is aggravated in the case of testers incorporated into a package since the entire package must be carried separately.

USPTO accepted both patents, despite the obvious overlap—in part, according to a 1996 article originally published by The Wall Street Journal, because of internal complexity within the patent office that ensured patent examiners in different parts of the office didn’t know what the other was doing.

“They’ve acknowledged that these are two patents issued which disclose the same invention,” said Peter W. Peterson, a lawyer with Strategic Energy, the firm created to manage the invention by Burroughs and O’Kain, in the article.

The legal battle was clearly intended to wear the smaller players down, with lawyers for Kodak attempting to poke holes in the language used in the other patent, but by early 1998, Kodak lost its initial case with a patent appeals board, with the office criticizing the “nit-picking” Kodak’s lawyers did. The smaller inventors expected more legal action.

“I’ve long had the feeling that big companies would drown us in legal bills,” Burroughs said told The Wall Street Journal.

O’Klein added that it was only the royalty fees from Eveready that allowed the smaller players to stay in the game. “If we didn’t have that, we’d be crushed,” he said.

The Gillette-owned Duracell continued to push legal action, but the USPTO ultimately favored the small inventors in a case that was full of legal grind. But ultimately, the legal battle came down to a simple fact: The little guys probably invented their take on the battery-tester technology first. As the Rochester Democrat and Chronicle noted, that would be hard for Kodak to work around.

The legal saga likely punctured a hole in the market for on-battery power meters. The result is that, today, this innovation, despite arguably being quite useful for most consumers, is relatively rare to see on batteries that you buy today. Duracell still offers them on some of its high-end battery models, but it’s not like a default feature, as it was in the mid-1990s.

A lot of us probably still rely on the flashlight approach.


The growth in battery sales during 1996, the year the battery tester first hit the shelves, according to research reported by Supermarket News at the time. Despite the usefulness of the feature, according to the trade publication, neither Duracell or Energizer could compete with the advantage that its generic competitors have on store shelves—price. The legal battle also failed to shake up the position of the market, with Duracell remaining on top with market share. “We have always had a strong market for batteries, but I have not seen any particular increase in sales due to the introduction of the on-battery testers,” one grocery manager told the publication.

As I said before, one thing that’s nice about this strange timeline we’re living in is that removable alkaline batteries have started to fade from the conversation to some degree in favor of longer-lasting batteries, though it would sure be nice if those batteries were easy for users to replace.

Certainly, it’s less wasteful for a single battery to die after four years of recharging than to throw away potentially hundreds of batteries used in a given device over a period of years. Neither are particularly great in landfills, but one makes a bit less physical waste along the way.


Spent batteries are still a problem. (PublicDomainPictures/Pixabay)

So why did the on-battery power meter fail? I think it’s because, despite the novel nature of putting a meter inside of a battery, it was ultimately a bridge technology, something that helped prop up the alkaline battery for a little while longer, but would ultimately be outmoded by the gradual shift to more modern battery technologies such as lithium-ion or even rechargeable batteries. I’ve written about bridge technologies in the past—the email appliance that lets you write messages without a computer is a great example of one.

The battery tester was a cool feature, a flashy one, but in its own way, it pointed out a weakness in how alkaline batteries work. Other technologies would come along and do a better job of solving the actual problem.


Find this one an interesting read? Share it with a pal!

Ernie Smith

Your time was just wasted by Ernie Smith

Ernie Smith is the editor of Tedium, and an active internet snarker. Between his many internet side projects, he finds time to hang out with his wife Cat, who's funnier than he is.

Find me on: Website Twitter