WEBVTT Kind: captions Language: en 00:00:00.120 --> 00:00:03.843 If you were a kid some time before, say, 2010, 00:00:03.843 --> 00:00:08.407 there was a phrase your parents probably learned to be quite irritated by: 00:00:08.407 --> 00:00:10.633 batteries not included. 00:00:10.633 --> 00:00:15.799 Our gadgets and gizmos used to be quite reliant on the good ol’ AA battery or, 00:00:15.799 --> 00:00:19.792 if designers wanted to be annoying, the AAA battery. 00:00:19.792 --> 00:00:25.853 Look, there’s not a huge difference in size between  the AA and the AAA and they usually cost the same per battery 00:00:25.853 --> 00:00:31.813 so whenever some engineer out there decides that a thing which could clearly fit longer-lasting AA batteries in it 00:00:31.813 --> 00:00:35.821 will go with just as expensive but shorter-lived AAAs instead, 00:00:35.821 --> 00:00:37.664 I get a wee bit angry. 00:00:37.664 --> 00:00:39.893 I mean, just look at this remote control. 00:00:39.893 --> 00:00:43.638 It could totally fit AAs in there, just look at how much extra room th - 00:00:43.968 --> 00:00:46.402 wait is that a Duracell PowerCheck? 00:00:46.402 --> 00:00:48.287 Indeed it is! 00:00:48.287 --> 00:00:52.540 If you were buying batteries in the late ‘90s, you probably remember these. 00:00:52.540 --> 00:00:59.503 The idea was that rather than need to use some sort of  battery tester to see if a battery still had any charge left in it, 00:00:59.503 --> 00:01:02.476 you could build that tester into the battery. 00:01:02.476 --> 00:01:06.209 And that’s what Duracell did - as well as some of their competitors. 00:01:06.209 --> 00:01:09.684 As a matter of fact this version of the idea came from Kodak, 00:01:09.684 --> 00:01:14.770 and there’s a whole fascinating story around patent disputes which I won’t be getting into 00:01:14.770 --> 00:01:21.459 (long story short, James R. Burroughs had a similar but technically different idea slightly earlier than Kodak 00:01:21.459 --> 00:01:28.439 but both patents got approved which caused some kerfuffles - I’ve linked to a great article down below which explains all that). 00:01:28.439 --> 00:01:34.195 Here, I just want to focus on how the Duracell version worked, because it’s quite clever! 00:01:34.195 --> 00:01:38.278 But also much much simpler than you might have imagined. 00:01:38.360 --> 00:01:43.391 If you want to test a battery like this, you’re going to want to measure its voltage. 00:01:43.391 --> 00:01:51.235 Like most battery chemistries, ordinary alkaline manganese dioxide cells experience a drop in voltage as they discharge. 00:01:51.235 --> 00:01:56.807 When fresh each cell has a voltage around 1.5, maybe 1.6 volts 00:01:56.807 --> 00:02:02.421 (and the standard AA, AAA, C, and D batteries are composed of just a single cell, 00:02:02.421 --> 00:02:04.033 like an amoeba!). 00:02:04.033 --> 00:02:08.329 But that voltage steadily diminishes as the battery is used up. 00:02:08.329 --> 00:02:16.703 When you’re halfway through it’ll be down to around 1.2 volts and when it’s near empty it’ll struggle to produce even a single volt. 00:02:16.703 --> 00:02:21.451 So, a quick check of a battery can be done with a multimeter like this one. 00:02:21.451 --> 00:02:25.454 If I use it and probe across this battery here, 00:02:25.454 --> 00:02:31.431 it's reading 1.57 volts so this is either brand new or hardly used. 00:02:31.431 --> 00:02:37.906 This one, though, it's only reading 1.06 so it’s pretty dead. 00:02:37.906 --> 00:02:44.324 This test isn’t perfect because we’re not checking the batteries under a load, but it’s still fairly reliable. 00:02:44.324 --> 00:02:51.029 Trouble is, you need a multimeter to do this as well as the  knowledge of how much voltage drop is acceptable before it's dead. 00:02:51.280 --> 00:02:59.759 So lots of inexpensive battery testers were made  which are really just analog voltmeters with a scale that reads good and bad. 00:02:59.759 --> 00:03:04.633 But what if you could build a voltmeter into the battery itself? 00:03:04.633 --> 00:03:11.716 Well, that’s ultimately what Duracell did with these batteries, but the way they work is a little… odd. 00:03:11.716 --> 00:03:18.184 First, you’ll notice that the battery says to test it at 70 degrees Fahrenheit or 21 degrees Celsius. 00:03:18.184 --> 00:03:24.683 That probably means the tester’s functionality has something to do with temperature, and indeed it does. 00:03:24.683 --> 00:03:28.905 But before I get ahead of myself, let me just show you how these were used. 00:03:28.905 --> 00:03:33.915 It says “press dots to test” and, well, that’s all you had to do. 00:03:33.915 --> 00:03:38.656 Except… if you remember these you’ll know that you had to press quite hard. 00:03:38.656 --> 00:03:41.021 Dig your nails in there a little bit. 00:03:41.021 --> 00:03:47.478 Once you did it though, the little bar below the power gauge would suddenly turn yellow, filling up from right to left. 00:03:47.478 --> 00:03:50.677 If the whole bar turned yellow, the battery was full. 00:03:50.677 --> 00:03:54.833 And less and less of it would turn yellow as the battery wore down. 00:03:54.833 --> 00:04:03.137 Now, with a use by date of March 2003 it probably won’t surprise you to learn that these batteries are in fact very dead. 00:04:03.137 --> 00:04:08.951 I got the tester to turn yellow with a little movie magic involving a foot switch and a hair dryer. 00:04:08.951 --> 00:04:12.636 Because heat is what turns that little bar yellow. 00:04:12.636 --> 00:04:21.101 Behind that little window is a small amount of thermochromic material, which as the name implies changes color based on temperature. 00:04:21.101 --> 00:04:26.951 It’s the same sort of stuff that goes in a mood ring or one of those thermometers you might stick on an aquarium. 00:04:26.951 --> 00:04:34.915 The specific chemical in here is simpler - it merely indicates it’s above a certain temperature threshold, but it’s the same general idea. 00:04:34.915 --> 00:04:36.801 What makes it heat up, though? 00:04:36.801 --> 00:04:44.526 Well you may have noticed that the testing window is perfectly in-line with the two dots you’re supposed to press to test the battery. 00:04:44.526 --> 00:04:49.183 The tester is built into the battery’s label, which I’ve removed from this one. 00:04:49.183 --> 00:04:55.095 In case you’ve never seen an unwrapped alkaline battery before, well this is what they look like. 00:04:55.095 --> 00:05:02.581 The positive terminal is actually part of the battery’s shell, and it extends almost all the way down to the negative terminal. 00:05:02.581 --> 00:05:06.187 A small insulator separates the negative tab from the shell. 00:05:06.187 --> 00:05:09.591 And if we compare with one of the still-wrapped batteries, 00:05:09.591 --> 00:05:15.624 we’ll see that one of the testing dots rests on the negative terminal and the other rests on the battery’s shell 00:05:15.624 --> 00:05:19.316 (which, remember is the positive terminal of the battery). 00:05:19.316 --> 00:05:26.759 Looking now at the backside of the label, we’ll see that those testing dots are above electrically conductive pads. 00:05:26.759 --> 00:05:33.091 The pads on the negative side are very difficult to see, they’re these three grey patches which don’t look all that impressive, 00:05:33.091 --> 00:05:38.603 but the positive contact patch is quite obviously a metal foil of some sort. 00:05:38.603 --> 00:05:45.525 And the contact patch sits behind a round hole in a thin piece of beige insulating material. 00:05:45.525 --> 00:05:53.439 That insulating layer keeps the pad from touching the battery shell unless you actively press on the label and force it through. 00:05:53.439 --> 00:06:01.680 If you exert enough force on both dots for their respective contact patches to touch both ends of the battery, you complete a circuit. 00:06:01.680 --> 00:06:03.725 To what, you ask? 00:06:03.725 --> 00:06:05.891 A tiny little heater. 00:06:05.891 --> 00:06:12.026 That heater is in contact with the thermochromic material, so if the battery has sufficient charge, 00:06:12.026 --> 00:06:18.853 when you press in those dots and complete the circuit, the heater will warm up the indicator and turn it yellow. 00:06:18.853 --> 00:06:21.670 But it’s not quite that simple. 00:06:21.670 --> 00:06:28.641 While you could just use a very thin wire heating element, that would only allow for a simple pass/fail test. 00:06:28.641 --> 00:06:34.307 If the battery had enough oomph  left to produce enough heat to make the indicator yellow, great! 00:06:34.307 --> 00:06:38.318 But you wouldn’t necessarily know how much oomph it had left. 00:06:38.318 --> 00:06:47.080 So instead, the heater has a varying cross-sectional area to produce a gradient of heat output across its length. 00:06:47.080 --> 00:06:51.891 If I remove that paper insulator, we can actually see the heater. 00:06:51.891 --> 00:06:53.591 Kind of, anyway. 00:06:53.591 --> 00:07:00.633 I’m not sure exactly what it’s made of - it might actually just be the same foil that makes up the contact patch. 00:07:00.633 --> 00:07:08.400 Regardless, it is visible and you’ll notice that it has a slight taper, becoming narrower towards the negative end of the battery. 00:07:08.400 --> 00:07:18.920 That means its resistance actually varies across its length, which also means the voltage drop across each part of this heater when it’s operating is different.   00:07:18.920 --> 00:07:26.694 If the battery is strong enough, its voltage will be sufficient to heat the entire thing, so all of the indicator turns yellow. 00:07:26.694 --> 00:07:29.520 But if the battery is getting weak and voltage begins to fall, 00:07:30.120 --> 00:07:34.551 then only the skinny, high-resistance part of the heater will get warm. 00:07:34.551 --> 00:07:38.215 Most of the voltage drop occurs in that part of the heater, 00:07:38.215 --> 00:07:45.160 and the battery doesn’t have any more volts for the rest of it, so only that part gets warm enough to turn the indicator yellow. 00:07:45.160 --> 00:07:49.405 And luckily I can show you this with a DC power supply. 00:07:49.405 --> 00:07:55.888 When I provide this with just 1 volt, you’ll see that only the right side of the graphic turns yellow. 00:07:55.888 --> 00:08:03.504 To clarify, the indicator always turns yellow at the same temperature, and the entire bar is filled with the same indicator. 00:08:03.504 --> 00:08:12.481 But low voltages (caused by a weak battery) can only get the skinny part of the heater warm enough to actually change the indicator’s color. 00:08:12.708 --> 00:08:18.700 But when I crank the voltage up, now all of it gets warm and so the whole bar turns yellow. 00:08:18.700 --> 00:08:27.807 And of course the bar is aligned with the zero to 100% scale to give a reasonably accurate impression of the battery’s useful life remaining. 00:08:27.807 --> 00:08:33.753 It’s a very elegant solution using tech so simple that it can be printed on a label. 00:08:33.753 --> 00:08:36.325 Oh, and remember that beige insulator? 00:08:36.325 --> 00:08:41.686 Turns out it’s not just electrically insulating, it’s also thermally insulating. 00:08:41.686 --> 00:08:50.019 That slot cut into it is there to maintain an air gap between the heater and thermochromic material and the battery shell. 00:08:50.019 --> 00:08:58.767 The battery shell is made of thermally-conductive material and it’s rather massive, so if the tester were in physical contact with the battery shell, 00:08:58.767 --> 00:09:04.340 it would suck all the heat right out of it and it would never turn the indicator yellow. 00:09:04.340 --> 00:09:08.328 Keeping it away from the battery is necessary for the indicator to function, 00:09:08.328 --> 00:09:18.561 so the same piece of what’s essentially just paper is functioning as both a crude power switch for the tester and thermal isolation for the indicator. 00:09:18.561 --> 00:09:19.709 Neat. 00:09:19.709 --> 00:09:24.686 You might have realized that since the  battery is powering a heater to test itself, 00:09:24.686 --> 00:09:29.124 that means each time you test it you’re using up a little bit of its capacity. 00:09:29.124 --> 00:09:36.970 And this is true - though it also means the test is slightly  more accurate since you’re doing it under a load. 00:09:36.970 --> 00:09:43.333 It’s not like the actual scale here is all that  accurate but testing under load is critical. 00:09:43.333 --> 00:09:52.984 These 25 year old batteries test at about 1.3 volts on the multimeter, which would suggest they’ve got about half their capacity remaining. 00:09:52.984 --> 00:09:57.748 But their ability to produce any current flow is completely shot. 00:09:57.748 --> 00:10:01.602 If I manage to activate the tester while also probing the battery, 00:10:01.602 --> 00:10:08.045 you’ll see that the voltage plummets to not even half a volt as the heater is placed in-circuit. 00:10:08.045 --> 00:10:14.685 So, sure enough, these batteries are dead and their inbuilt tester does actually reflect that. 00:10:14.685 --> 00:10:16.471 Yet the multimeter doesn’t. 00:10:16.471 --> 00:10:19.864 So then… why did it go away? 00:10:19.864 --> 00:10:28.765 Duracell PowerCheck was a pretty short blip on the landscape of disposable batteries yet it’s clearly a useful, functional feature. 00:10:28.765 --> 00:10:36.371 Well, the patent disputes and licensing shenanigans are  one clear reason but I honestly think there’s a simpler one: 00:10:36.371 --> 00:10:41.705 not that many people were actually testing their batteries on a regular basis! 00:10:41.705 --> 00:10:49.258 Yes, we all know about the loose batteries in the junk drawer that may or may not save the TV remote in a trying time, 00:10:49.258 --> 00:10:52.001 but aside from random situations like that, 00:10:52.001 --> 00:10:59.240 I think it’s fair to say most people used and continue to  use batteries in a pretty straightforward way: 00:11:00.240 --> 00:11:06.280 they simply stay new in the package until they  get put into a thing which needs batteries,   00:11:06.280 --> 00:11:11.040 and then they stay in that thing until they  die, at which point they’re gotten rid of   00:11:11.040 --> 00:11:14.489 and another set of fresh batteries replaces them. 00:11:14.489 --> 00:11:22.880 I’d argue it’s pretty uncommon to take partially-used batteries out of a thing and then put them in the junk drawer for later use. 00:11:22.880 --> 00:11:25.586 I’m not saying I think that never happens - 00:11:25.586 --> 00:11:33.330 I myself have a few tools which need batteries but I don’t keep batteries in them since I rarely use those tools. 00:11:33.330 --> 00:11:39.937 But I do think in the grand scheme, keeping half-used batteries around is infrequent. 00:11:39.937 --> 00:11:49.511 Certainly infrequent enough to question whether it actually makes sense to spend the money putting a battery tester on every single battery. 00:11:49.511 --> 00:11:57.058 These are commodity items, and while there surely is some  brand loyalty out there for the most part they’re competing on cost, 00:11:57.058 --> 00:12:06.138 and so if you need a pack of batteries and you use them like I do, a built-in battery tester is just a weird gimmick which makes them more expensive 00:12:06.138 --> 00:12:09.331 (and makes me less likely to buy it). 00:12:09.331 --> 00:12:14.600 And as I already said,  if you remember these, they weren’t easy to use! 00:12:14.600 --> 00:12:20.724 It was actually quite frustrating to jam those  dots in there and hope it turned yellow. 00:12:20.724 --> 00:12:29.917 And if I were the type of person who kept partially-used batteries in random places, I would probably just buy a battery tester and keep it around. 00:12:29.917 --> 00:12:35.573 Or, ya know, just try putting them in whatever needs batteries  and see if they work. 00:12:35.573 --> 00:12:37.699 That was always an option. 00:12:37.699 --> 00:12:49.219 I think that in hindsight, this is a pretty clear case of a really clever, and very neat idea which was unfortunately born from a very particular frustration. 00:12:49.219 --> 00:12:54.354 A frustration that the inventors thought  was more common than it actually was. 00:12:54.354 --> 00:13:03.125 Duracell used to include inexpensive battery testers in the packages of their batteries, and they worked very similarly to the PowerCheck feature here. 00:13:03.125 --> 00:13:08.366 Some people found them hard to use, or were bothered by the fact that they were easy to lose, 00:13:08.366 --> 00:13:11.760 and that could be seen as a legitimate problem to solve. 00:13:11.760 --> 00:13:16.244 Which Duracell did by incorporating those testers into the battery! 00:13:16.244 --> 00:13:23.393 But I don’t think anyone asked how  often those testers were actually getting used in the first place. 00:13:23.393 --> 00:13:27.942 Because if they had, I’m not sure this would have ever happened. 00:13:27.942 --> 00:13:33.683 Of course these days, most of our devices which need batteries are using rechargeable batteries, 00:13:33.683 --> 00:13:39.097 so we’re just not buying or using disposable batteries as much as we used to. 00:13:39.097 --> 00:13:42.431 Which I think is unequivocally a good thing! 00:13:42.431 --> 00:13:48.284 It’s kinda nuts how normal it used to be to burn through these and then just throw ‘em away. 00:13:48.284 --> 00:13:52.812 I had a Game Boy and that one device  must have gone through dozens of these. 00:13:52.812 --> 00:13:57.154 And then there was the Walkman, my camera, the light for the game boy, 00:13:57.154 --> 00:14:02.302 and who knows how many other toys I had which needed constant battery replenishment. 00:14:02.302 --> 00:14:04.948 Thank goodness we’re past that. 00:14:04.948 --> 00:14:06.184 Mostly. 00:14:06.184 --> 00:14:10.085 Uh, but even for the devices on sale today which need AA batteries? 00:14:10.085 --> 00:14:18.968 They often tell you how much charge is left so putting a tester on the battery itself really just isn’t necessary anymore. 00:14:18.968 --> 00:14:21.120 Alright, well I think we’re done. 00:14:21.120 --> 00:14:26.258 I want to extend a thank you to Luis Solano for suggesting this video topic. 00:14:26.258 --> 00:14:31.975 It’s been on the docket for a while but, uh, well these haven’t been in production for quite some time 00:14:31.975 --> 00:14:35.134 so it took me a while to get my hands on them. 00:14:35.134 --> 00:14:38.179 And I have a second thank you for Ernie Smith - 00:14:38.179 --> 00:14:44.897 this is at least the second time my research began and immediately I was presented with a thorough Tedium article. 00:14:44.897 --> 00:14:50.290 I would have gone more deeply here were it not for the  fact that this video was originally slated for November 00:14:50.290 --> 00:14:53.714 but production issues on a different topic moved it up to now, 00:14:54.126 --> 00:15:00.793 so if you’re interested in those patent details and some of the backstory, be sure to check out the link in the description. 00:15:01.987 --> 00:15:05.939 Normally I try to put something clever here but I think I’m all out of juice. 00:15:06.866 --> 00:15:09.462 ♫ exhaustedly smooth jazz ♫ 00:15:10.868 --> 00:15:14.236 like most battery chemistries, ordinary alkaline magaz— 00:15:14.236 --> 00:15:15.935 magazine? 00:15:15.935 --> 00:15:18.244 Are you subscribed to Alkaline Magazine? 00:15:18.244 --> 00:15:24.867 Lots of inexpensive battery testers were made which are really just analog voltmeters with a scale that ride— 00:15:26.668 --> 00:15:27.252 DANG IT 00:15:27.252 --> 00:15:29.452 Kind of. I'm not exactly... 00:15:29.452 --> 00:15:30.726 oh I don't like that delivery 00:15:30.726 --> 00:15:33.694 ...but there ability to produce any curr...mmmmnaAAGH 00:15:33.694 --> 00:15:37.088 ...plummets to not even half a volt as the plater... 00:15:37.088 --> 00:15:38.595 mehah huhhh 00:15:38.595 --> 00:15:43.627 It was actually kind of frustrating to push these dots in and wait for it to light up. 00:15:43.627 --> 00:15:46.640 And if I were the type of person who kept part- 00:15:46.640 --> 00:15:49.676 yep, I can't say "light up" I'll get pedanted for that. 00:15:49.676 --> 00:15:53.621 If I were the type of person who kept randomly used partially used 00:15:53.621 --> 00:15:54.975 aaaaahggghhh! 00:15:56.929 --> 00:16:01.827 So apparently these were made for much longer in some markets and also hung around for a while here in the US on some of the high-end batteries Duracell sold. 00:16:01.827 --> 00:16:06.161 TBH I had no idea but mostly because I'm a value-obsessed Midwesterner who mostly buys generics 00:16:06.161 --> 00:16:09.029 (or might splurge for Rayovac if it's on-sale). 00:16:09.029 --> 00:16:10.920 Does this count as an end-captions gag? 00:16:10.920 --> 00:16:12.004 You decide!