2680: Battery Life

Explain xkcd: It's 'cause you're dumb.
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Battery Life
It's okay, I'm at 10%, so I'm good for another month or two.
Title text: It's okay, I'm at 10%, so I'm good for another month or two.


Smartphones run on batteries that require frequent charging; they may also be frequently replaced with a newer model by their user, though battery life is only one of several reasons why they may do this. In this comic, instead of charging his phone every day for a few years and then buying a new phone, Cueball has obtained a phone with a battery big enough to last supposedly until the phone will be replaced after a few years. This appears to make for a phone of cumbersome weight and size. According to the caption, 10% of battery life corresponds to 1–2 months; this suggests a total battery life and hence product life of 10–20 months, which is less than two years. A 'few' is generally more than that, even in the world of xkcd. (This assumes that he'd be 'good' right up until 0%. He could be just talking about being generally unconcerned until it reaches 5%, say, from which point he knows he'll have a similar further amount of time to start seriously thinking about arranging the full replacement, and all that this entails.) More practically, a smartphone requires around 2 kWh per year (assuming this is not otherwise an untypical phone in terms of power requirements), so this 12 kWh battery could have been expected to last even longer.

A 12 kWh battery weighing 100 pounds (45 kg) has an energy density of 264.6 Wh/kg, about equal to the high-estimate of the energy density of lithium-ion batteries of 100–265 Wh/kg. However, it is well below the practically achievable energy densities of (non-rechargeable, as befits the application) zinc-air batteries at around 400 Wh/kg. Unfortunately, Self-discharge means that if this battery is lithium polymer, it will lose on average 5% of its charge per month, which totals to 46% lost each year. If this were a non rechargeable battery such a lithium metal, its battery life could be much longer.

This comic appeared on the same day that the European Union standardized charging adapters for mobile phones.

This may be a commentary on very large external portable charging devices. At present (October, 2022) the largest cell-phone sized charging devices hold almost 40000mAh and can weigh almost a pound. Even larger devices are available weighing over 40 lbs in different form factors. We buy cell phones because of their small size and convenience,[citation needed] and end up buying extra external battery power for them that adds significant extra weight and bulk.

Portable (on wheels) 12 kWh lithium-ion batteries do exist but typically weigh over 250 lbs and tend to lack ports to plug a phone directly into. Roughly 100 lb portable power stations can have capacities as high as 6 kWh and can be used to charge a typical smartphone directly hundreds of times.


[Cueball is seen carrying a large box. He is shown three times as he seems to turn and walk to the right in the same panel. He has trouble reaching around the box. In the first version a label can be seen at the bottom of the box, which indicated it is a huge battery. There are also unreadable text at the top. Cueball holds it in front of him, covering his torso and partly obscuring his head. In the second version he has turned to the right, and reveals that on the other side of the box there is a small phone in the middle with a keyboard. In the last version he has turned fully and it looks like he is walking to the right, but could also be that he is just leaning back to support the weight of the box. He is operating the phone with a free hand while he holds the box with the other hand, and are thus forced to lean it against his head for support.]
Label: 12 kWh
[Caption beneath the panel:]
Plugging in my phone is a pain, so I got one with a 100lb battery, and when it runs out of charge every few years I just upgrade.

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I found a source saying phones need 1 kWh/year, to the closest 10 kWh. That's quite strange. Better source needed? --While False (speak|museum) 04:32, 4 October 2022 (UTC)

/\--- The article cited is from 2013, so quite old, and within the article it even amends the tagline value to 2kWh. iPhone 12 would last about 47 days with a 12kWh battery based on specs (2,815mAh battery, nom voltage 3.8V) and assuming that a charge lasts a full day. 15:44, 4 October 2022 (UTC) JourneymanWizard

An average iPhone has somewhere around 12 Wh of capacity, which at 1 kWh/year would imply only ~23% per day. Anecdotally, that's definitely not right. An IEEE article claims 4 kWh/year, but I don't have access and only see this in the Google snippet. -- 05:37, 4 October 2022 (UTC)

  • What about my S series Samsung?

It has 5000mAh battery, 3,7V voltage, ergo (5 amper * 3,7 volt) = 18,5 watts/hour. It lasts for, roughly, 1 day of heavy use at work (camera, youtube etc., its was my media device) and 2 days of weekend use.

My phone has been in use for 4 years before an upgrade, which gives 366+365+365+365=731+730=1461 day. 1467/7*6 full recharges -- ~1253 recharges. 1253*18,5Wh gives ~18,5kWh*5/4 --- 23,09 kWh; 5,6 kWh per year. 07:18, 4 October 2022 (UTC)

Very old (1980s?) relevant joke preserved at https://www.ariel.com.au/jokes/The_Inventor.html
Jake is struggling through a bus station with two huge and obviously heavy suitcases when a stranger walks up to him and asks "Have you got the time?"
Jake sighs, puts down the suitcases and glances at his wrist. "It's a quarter to six," he says.
"Hey, that's a pretty fancy watch!" exclaims the stranger. Jake brightens a little.
"Yeah, it's not bad. Check this out" - and he shows him a time zone display not just for every time zone in the world, but for the 86 largest metropolises.
He hits a few buttons and from somewhere on the watch a voice says "The time is eleven 'til six" in a very West Texas accent. A few more buttons and the same voice says something in Japanese. Jake continues "I've put in regional accents for each city". The display is unbelievably high quality and the voice is simply astounding.
The stranger is struck dumb with admiration. "That's not all", says Jake. He pushes a few more buttons and a tiny but very high-resolution map of New York City appears on the display. "The flashing dot shows our location by satellite positioning," explains Jake.
"View recede ten", Jake says, and the display changes to show eastern New York state.
"I want to buy this watch!" says the stranger.
"Oh, no, it's not ready for sale yet; I'm still working out the bugs", says the inventor.
"But look at this", and he proceeds to demonstrate that the watch is also a very creditable little FM radio receiver with a digital tuner, a sonar device that can measure distances up to 125 meters, a printer with thermal paper printout and, most impressive of all, the capacity for voice recordings of up to 300 standard-size books, "though I only have 32 of my favorites in there so far" says Jake.
"I've got to have this watch!", says the stranger.
"No, you don't understand; it's not ready -"
"I'll give you $1000 for it!"
"Oh, no, I've already spent more than -"
"I'll give you $5000 for it!"
"But it's just not -"
"I'll give you $15,000 for it!" And the stranger pulls out a checkbook.
Jake stops to think. He's only put about $8500 into materials and development, and with $15,000 he can make another one and have it ready for merchandising in only six months. The stranger frantically finishes writing the check and waves it in front of him. "Here it is, ready to hand to you right here and now. $15,000. Take it or leave it."
Jake abruptly makes his decision. "OK", he says, and peels off the watch.
They make the exchange and the stranger starts happily away. "Hey, wait a minute", calls Jake after the stranger, who turns around warily.
Jake points to the two suitcases he'd been trying to wrestle through the bus station. "Don't forget your batteries."
Duard (talk) 02:34, 6 October 2022 (UTC)

  • Nice joke, but it feels like it's based on a similar Soviet joke (American engineers could afford cars while Soviet engis were carless). On a serious note, a really rich person (a "shark") could use such a watch for office use / car use.

"Plugging my phone is a pain" as a modern problem[edit]

While some folks (like myself) use long (3m/10ft) cords, most people are stuck with 1m charging cables or less. That's indeed a pain if you use your phone a lot. It's also frustrating to deal with charging cables getting old while your phone's charging port is also getting old. However, Energizer's take on the problem (custom 18000mAh phone) doesn't feel good either: the resulting phone feels too heavy. A hefty brick of a ~18000mAh powerbank itself is already too heavy for many pockets, even outside of "skinny jeans" fashion. 08:47, 4 October 2022 (UTC)

  • Oh! By the way, last week, I almost got into a problem. I plugged my phone, went to sleep, woke up without an alarm and assumed it is too early to get out of bed. Then, the street noises made me realize it's actually 9AM already and I am late for work. "So much for XXI century smart devices", I thought. 08:51, 4 October 2022 (UTC)
In many ways, smart phones were step backward. My old Nokia phone is easier to hold in hand and can sound an alarm when TURNED OFF (obviously, there is separate circuit for counting time to alarm which remains powered). Granted, for playing games, I needed to buy a separate android game console which is sold as smartphone. -- Hkmaly (talk) 12:13, 4 October 2022 (UTC)
Funny thing is, early smarties had such a feature as well. Bottom-of-the-barrel cheap Micromax A28 had it (and it was very loud). IIRC, Asus ZenPad (or ZenFone, with 4G) had it as well, shutting down at 4% charge just to have some energy to ring the alarm. 20:12, 6 October 2022 (UTC)

Out of interest, how many people replace their phone because of the battery? There are those who would replace their xkcdPhone3000aIII for an xkcdPhone3000aIV just because you only get the blue-anodised casing with the latter and the limited-edition red-anodised case of the former is so last week (actually, probably only out six days ago). There are those who will swap when the OS gets a new version (because they might be missing out). There are those who will have to swap because NewApp doesn't support "Pancake" or "Sausagedog" or whatever version of OS it is that's now a year or three behind the curve. There are those who will swap because OldApp is no longer supporting "DoritoSandwiches" (the 5yo OS on their very well-used device) and they actually don't like giving up on it. Then there are those who will just make do with a dwindling capability (various apps going inoperable, but those that aren't are still being used whilst the rest of the device still works!). And, by the end of that list, you can be sure a charger-plug and/or powerbank is an "Everyday Carry", possibly even an always plugged in essential because even phone/tablet repair places are starting to tell you that they couldn't guarantee to get a replacement battery of the right vintage, or you find out for yourself how hard it was to effect a full repair/transplant. — For the record, I'm definitely towards this end of that list (but get a newer device to run in parallel, to probably start to consider just as unretirable as its working life starts to be compromised, at various times having perhaps three 'working' generations of device, none of them the current bleeding-edge). 13:14, 4 October 2022 (UTC) — P.S.: And, so far, I have never continued the same (Android/Google) account over to a new device, or worked out how to migrate apps(+data) wholesale across devices, where not already designed with export/import facilities or just have to have the same non-device login details carried over to a sign-in/up dialogue. Must be possible/expected, but I've just never ever tried it. New device, new Gmail! 13:22, 4 October 2022 (UTC)

I decided to upgrade my aforementioned 4 year old smartphone because it used to be a "flagship phone" and now it's a phone with OK perfomance, great display yet low battery life. So yes, it was the "cannot be bothered with the [somewhat degraded] battery" problem. 14:18, 5 October 2022 (UTC)
In fact, my 2017 device initially got all those "charging problems" as well, due to playing too much Ingress on foot. 14:20, 5 October 2022 (UTC)
I did bought new phone when the old one not only wasn't able to run on "full" battery for longer than 20 seconds, but when the connected powerbank was not enough to keep it running. However, I suspect that the battery life was shortened by using it in winter(s) and that the powerbank itself had problem as well. -- Hkmaly (talk) 12:02, 6 October 2022 (UTC)
My old phone only got ditched because both the original battery and a spare had both got to the point of not holding more than a couple of hours' charge. 12:09, 6 October 2022 (UTC)
Apart from the battery, there is the fact that most smartphone vendors stop providing OS updates after two years and leave you with remote-exploits in the bluetooth stack or media libraries. I tried cyanogenmod and lineageos in the past to extend the useful life, but it needs quite some effort and compromises. Bmwiedemann (talk) 12:06, 17 January 2024 (UTC)

Anyone else notice that in the third image, Cueball is supporting a 100lb+ phone with one arm, while fiddling with the screen with his other hand? Impressive balance to be able to support a 100lb object with one arm while still standing fully upright. 14:58, 4 October 2022 (UTC)

It was just a few years ago that the idea of replacing a failing battery was abandoned. With batteries lasting longer and phone generations being shorter, most users would see only a small reduction in time between charges by the time they would be upgrading anyway. I interpreted the comic as the logical next step in that evolution. 19:45, 4 October 2022 (UTC)

I don't get what this one is supposed to be about. https://techxplore.com/news/2022-10-eu-lawmakers-impose-charger-smartphones.html ? 01:40, 5 October 2022 (UTC)

  • Type-C for everyone? I think it's all about the 5V voltage as a "backup standard" for big phones, tablets and laptops. I have 2 smartphones with "fast charging" features. One can run 5V 2A or 9V 1,67A. Another one is a beast, it supports 10V 60W charging while still offering 5V 2A charge as a backup measure. Losing one charger would be unpleasant yet not serious -- another phone's charger would do the job. 20:16, 6 October 2022 (UTC)