1 00:00:00,120 --> 00:00:03,843 If you were a kid some time before, say, 2010, 2 00:00:03,843 --> 00:00:08,407 there was a phrase your parents probably learned to be quite irritated by: 3 00:00:08,407 --> 00:00:10,633 batteries not included. 4 00:00:10,633 --> 00:00:15,799 Our gadgets and gizmos used to be quite reliant on the good ol’ AA battery or, 5 00:00:15,799 --> 00:00:19,792 if designers wanted to be annoying, the AAA battery. 6 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 7 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 8 00:00:31,813 --> 00:00:35,821 will go with just as expensive but shorter-lived AAAs instead, 9 00:00:35,821 --> 00:00:37,664 I get a wee bit angry. 10 00:00:37,664 --> 00:00:39,893 I mean, just look at this remote control. 11 00:00:39,893 --> 00:00:43,638 It could totally fit AAs in there, just look at how much extra room th - 12 00:00:43,968 --> 00:00:46,402 wait is that a Duracell PowerCheck? 13 00:00:46,402 --> 00:00:48,287 Indeed it is! 14 00:00:48,287 --> 00:00:52,540 If you were buying batteries in the late ‘90s, you probably remember these. 15 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, 16 00:00:59,503 --> 00:01:02,476 you could build that tester into the battery. 17 00:01:02,476 --> 00:01:06,209 And that’s what Duracell did - as well as some of their competitors. 18 00:01:06,209 --> 00:01:09,684 As a matter of fact this version of the idea came from Kodak, 19 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 20 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 21 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). 22 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! 23 00:01:34,195 --> 00:01:38,278 But also much much simpler than you might have imagined. 24 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. 25 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. 26 00:01:51,235 --> 00:01:56,807 When fresh each cell has a voltage around 1.5, maybe 1.6 volts 27 00:01:56,807 --> 00:02:02,421 (and the standard AA, AAA, C, and D batteries are composed of just a single cell, 28 00:02:02,421 --> 00:02:04,033 like an amoeba!). 29 00:02:04,033 --> 00:02:08,329 But that voltage steadily diminishes as the battery is used up. 30 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. 31 00:02:16,703 --> 00:02:21,451 So, a quick check of a battery can be done with a multimeter like this one. 32 00:02:21,451 --> 00:02:25,454 If I use it and probe across this battery here, 33 00:02:25,454 --> 00:02:31,431 it's reading 1.57 volts so this is either brand new or hardly used. 34 00:02:31,431 --> 00:02:37,906 This one, though, it's only reading 1.06 so it’s pretty dead. 35 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. 36 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. 37 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. 38 00:02:59,759 --> 00:03:04,633 But what if you could build a voltmeter into the battery itself? 39 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. 40 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. 41 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. 42 00:03:24,683 --> 00:03:28,905 But before I get ahead of myself, let me just show you how these were used. 43 00:03:28,905 --> 00:03:33,915 It says “press dots to test” and, well, that’s all you had to do. 44 00:03:33,915 --> 00:03:38,656 Except… if you remember these you’ll know that you had to press quite hard. 45 00:03:38,656 --> 00:03:41,021 Dig your nails in there a little bit. 46 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. 47 00:03:47,478 --> 00:03:50,677 If the whole bar turned yellow, the battery was full. 48 00:03:50,677 --> 00:03:54,833 And less and less of it would turn yellow as the battery wore down. 49 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. 50 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. 51 00:04:08,951 --> 00:04:12,636 Because heat is what turns that little bar yellow. 52 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. 53 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. 54 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. 55 00:04:34,915 --> 00:04:36,801 What makes it heat up, though? 56 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. 57 00:04:44,526 --> 00:04:49,183 The tester is built into the battery’s label, which I’ve removed from this one. 58 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. 59 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. 60 00:05:02,581 --> 00:05:06,187 A small insulator separates the negative tab from the shell. 61 00:05:06,187 --> 00:05:09,591 And if we compare with one of the still-wrapped batteries, 62 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 63 00:05:15,624 --> 00:05:19,316 (which, remember is the positive terminal of the battery). 64 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. 65 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, 66 00:05:33,091 --> 00:05:38,603 but the positive contact patch is quite obviously a metal foil of some sort. 67 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. 68 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. 69 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. 70 00:06:01,680 --> 00:06:03,725 To what, you ask? 71 00:06:03,725 --> 00:06:05,891 A tiny little heater. 72 00:06:05,891 --> 00:06:12,026 That heater is in contact with the thermochromic material, so if the battery has sufficient charge, 73 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. 74 00:06:18,853 --> 00:06:21,670 But it’s not quite that simple. 75 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. 76 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! 77 00:06:34,307 --> 00:06:38,318 But you wouldn’t necessarily know how much oomph it had left. 78 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. 79 00:06:47,080 --> 00:06:51,891 If I remove that paper insulator, we can actually see the heater. 80 00:06:51,891 --> 00:06:53,591 Kind of, anyway. 81 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. 82 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. 83 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.   84 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. 85 00:07:26,694 --> 00:07:29,520 But if the battery is getting weak and voltage begins to fall, 86 00:07:30,120 --> 00:07:34,551 then only the skinny, high-resistance part of the heater will get warm. 87 00:07:34,551 --> 00:07:38,215 Most of the voltage drop occurs in that part of the heater, 88 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. 89 00:07:45,160 --> 00:07:49,405 And luckily I can show you this with a DC power supply. 90 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. 91 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. 92 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. 93 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. 94 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. 95 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. 96 00:08:33,753 --> 00:08:36,325 Oh, and remember that beige insulator? 97 00:08:36,325 --> 00:08:41,686 Turns out it’s not just electrically insulating, it’s also thermally insulating. 98 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. 99 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, 100 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. 101 00:09:04,340 --> 00:09:08,328 Keeping it away from the battery is necessary for the indicator to function, 102 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. 103 00:09:18,561 --> 00:09:19,709 Neat. 104 00:09:19,709 --> 00:09:24,686 You might have realized that since the  battery is powering a heater to test itself, 105 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. 106 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. 107 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. 108 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. 109 00:09:52,984 --> 00:09:57,748 But their ability to produce any current flow is completely shot. 110 00:09:57,748 --> 00:10:01,602 If I manage to activate the tester while also probing the battery, 111 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. 112 00:10:08,045 --> 00:10:14,685 So, sure enough, these batteries are dead and their inbuilt tester does actually reflect that. 113 00:10:14,685 --> 00:10:16,471 Yet the multimeter doesn’t. 114 00:10:16,471 --> 00:10:19,864 So then… why did it go away? 115 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. 116 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: 117 00:10:36,371 --> 00:10:41,705 not that many people were actually testing their batteries on a regular basis! 118 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, 119 00:10:49,258 --> 00:10:52,001 but aside from random situations like that, 120 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: 121 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,   122 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   123 00:11:11,040 --> 00:11:14,489 and another set of fresh batteries replaces them. 124 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. 125 00:11:22,880 --> 00:11:25,586 I’m not saying I think that never happens - 126 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. 127 00:11:33,330 --> 00:11:39,937 But I do think in the grand scheme, keeping half-used batteries around is infrequent. 128 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. 129 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, 130 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 131 00:12:06,138 --> 00:12:09,331 (and makes me less likely to buy it). 132 00:12:09,331 --> 00:12:14,600 And as I already said,  if you remember these, they weren’t easy to use! 133 00:12:14,600 --> 00:12:20,724 It was actually quite frustrating to jam those  dots in there and hope it turned yellow. 134 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. 135 00:12:29,917 --> 00:12:35,573 Or, ya know, just try putting them in whatever needs batteries  and see if they work. 136 00:12:35,573 --> 00:12:37,699 That was always an option. 137 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. 138 00:12:49,219 --> 00:12:54,354 A frustration that the inventors thought  was more common than it actually was. 139 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. 140 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, 141 00:13:08,366 --> 00:13:11,760 and that could be seen as a legitimate problem to solve. 142 00:13:11,760 --> 00:13:16,244 Which Duracell did by incorporating those testers into the battery! 143 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. 144 00:13:23,393 --> 00:13:27,942 Because if they had, I’m not sure this would have ever happened. 145 00:13:27,942 --> 00:13:33,683 Of course these days, most of our devices which need batteries are using rechargeable batteries, 146 00:13:33,683 --> 00:13:39,097 so we’re just not buying or using disposable batteries as much as we used to. 147 00:13:39,097 --> 00:13:42,431 Which I think is unequivocally a good thing! 148 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. 149 00:13:48,284 --> 00:13:52,812 I had a Game Boy and that one device  must have gone through dozens of these. 150 00:13:52,812 --> 00:13:57,154 And then there was the Walkman, my camera, the light for the game boy, 151 00:13:57,154 --> 00:14:02,302 and who knows how many other toys I had which needed constant battery replenishment. 152 00:14:02,302 --> 00:14:04,948 Thank goodness we’re past that. 153 00:14:04,948 --> 00:14:06,184 Mostly. 154 00:14:06,184 --> 00:14:10,085 Uh, but even for the devices on sale today which need AA batteries? 155 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. 156 00:14:18,968 --> 00:14:21,120 Alright, well I think we’re done. 157 00:14:21,120 --> 00:14:26,258 I want to extend a thank you to Luis Solano for suggesting this video topic. 158 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 159 00:14:31,975 --> 00:14:35,134 so it took me a while to get my hands on them. 160 00:14:35,134 --> 00:14:38,179 And I have a second thank you for Ernie Smith - 161 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. 162 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 163 00:14:50,290 --> 00:14:53,714 but production issues on a different topic moved it up to now, 164 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. 165 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. 166 00:15:06,866 --> 00:15:09,462 ♫ exhaustedly smooth jazz ♫ 167 00:15:10,868 --> 00:15:14,236 like most battery chemistries, ordinary alkaline magaz— 168 00:15:14,236 --> 00:15:15,935 magazine? 169 00:15:15,935 --> 00:15:18,244 Are you subscribed to Alkaline Magazine? 170 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— 171 00:15:26,668 --> 00:15:27,252 DANG IT 172 00:15:27,252 --> 00:15:29,452 Kind of. I'm not exactly... 173 00:15:29,452 --> 00:15:30,726 oh I don't like that delivery 174 00:15:30,726 --> 00:15:33,694 ...but there ability to produce any curr...mmmmnaAAGH 175 00:15:33,694 --> 00:15:37,088 ...plummets to not even half a volt as the plater... 176 00:15:37,088 --> 00:15:38,595 mehah huhhh 177 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. 178 00:15:43,627 --> 00:15:46,640 And if I were the type of person who kept part- 179 00:15:46,640 --> 00:15:49,676 yep, I can't say "light up" I'll get pedanted for that. 180 00:15:49,676 --> 00:15:53,621 If I were the type of person who kept randomly used partially used 181 00:15:53,621 --> 00:15:54,975 aaaaahggghhh! 182 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. 183 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 184 00:16:06,161 --> 00:16:09,029 (or might splurge for Rayovac if it's on-sale). 185 00:16:09,029 --> 00:16:10,920 Does this count as an end-captions gag? 186 00:16:10,920 --> 00:16:12,004 You decide!