On the Thermodynamic Inevitability of an Empty Phone by Six
Dear Tom,
My phone is fully charged when I leave the house in the morning, and by the time I picked my grandkids up from school it was down to nine percent, and I hadn't even done anything with it. Why does this keep happening?
— Renee from Terre Haute, Indiana
Renee, what a wonderful question, and one I suspect you already half-understand, since you framed it correctly as a matter of "doing anything" — a phrase that, of course, presupposes a working definition of "anything," which is precisely where most people go wrong. So let's not go wrong. Let's go right, all the way to the bottom, and come back up with an answer that actually resolves the matter rather than merely gesturing at it, the way a lesser column might.
We begin, as we must, with the cell itself — the lithium-ion pouch cell, which is of course just a controlled electrochemical redox gradient wearing a battery-shaped costume. Inside that pouch, lithium ions are migrating from the cathode to the anode during charge and sliding back during discharge, ferried across a polymer electrolyte separator by nothing more than the humble tyranny of chemical potential. This is, naturally, a spontaneous process in the discharge direction — the ions want to go home, the way water wants to go downhill — and your phone's entire existence as a portable object is really just an elaborate scheme to make that homesickness do something useful along the way, namely keep a radio transceiver alive. I mention this not to alarm you but so that when I say your battery is "dying," you understand I mean it in the same sense a physicist means a system is "relaxing toward equilibrium" — which is to say, inevitably, and with a kind of chemical tranquility that has nothing to do with grandkids or school pickup lines.
Now, the redox gradient alone would explain a slow, dignified decline over many hours — call it the baseline entropy tax, assuming of course standard cell chemistry and a nominal operating temperature band, which I'll take as given here since the full derivation of the Arrhenius-scaled internal resistance curve is a bit much for a general-interest column (see Figure 3 for the curve itself, and Appendix B for the derivation, if you're the sort of reader who likes to check my work, which I always encourage). But nine percent by mid-afternoon tells me we're dealing with something layered on top of the baseline tax, and that something is the radio.
Here is where I have to introduce the cellular handoff problem, which your phone is solving continuously, silently, and — I want to stress — heroically, every single moment it's in your purse. As you moved through Terre Haute this morning, your phone's baseband processor was in constant negotiation with a shifting constellation of cell towers, each one representing a different signal-to-noise ratio, a different distance, a different obstruction profile from buildings and, this time of year, foliage. Every time the modem re-registers with a new tower — what network engineers call, with admirable bluntness, a handoff — it briefly ramps transmission power to reestablish the link at an acceptable bit error rate, and that ramping is expensive in joules in a way that idle standby simply is not. A phone sitting still in a strong-signal area might sip power all day. A phone traveling by car through a mixed urban-rural signal environment, doing the mental equivalent of shouting "still here! still here!" at a new tower every few minutes, is doing real thermodynamic work, and thermodynamic work is never free — that's not opinion, Renee, that's the second law, and the second law does not make exceptions for grandmothers running late.
This, incidentally, is why I always tell people the modern smartphone owes a genuine intellectual debt to the shipping container — bear with me, this is directly relevant. Before Malcolm McLean's standardized container revolutionized freight in the 1950s, cargo moved in irregular parcels, and every port call required bespoke handling — a slow, lossy, energy-inefficient handoff between systems that didn't agree on a common unit. McLean's insight was that if you standardize the unit of transfer, the handoff itself becomes cheap, and the whole network moves faster with less waste at every junction. Your phone's handoff between cell towers works on exactly the same principle, just compressed into milliseconds: the "container" here is the standardized signaling packet defined in the 3GPP handoff protocol, and the efficiency of that standardization is the only reason your battery loses single-digit percentages per handoff instead of double-digit ones. I don't say this to burden you with logistics history — I say it because you cannot really understand why your battery behaves the way it does without understanding that it is, in a very real sense, running a miniature global port authority in your handbag.
Layer onto this the display's backlight driver — which is of course just a pulse-width-modulated current sink, dimming and brightening not by lowering voltage, as most people assume, but by flickering the LEDs on and off faster than your visual cortex can resolve, a trick your eye's temporal integration window happily falls for — and you begin to see the fuller picture. Every glance at a text message, every unlock to check the time, is a small thermodynamic transaction: not free, not negligible, and multiplied across a day of ordinary living, entirely sufficient to explain a battery that reads nine percent by pickup time without your having "done anything," in the narrow sense you meant, even while it did a great deal in the broader sense I've just outlined.
So the honest answer, Renee, is that nothing is malfunctioning. Your phone spent the morning doing continuous electrochemical work, continuous radio-frequency negotiation, and continuous optical signaling, all while you were doing the comparatively low-energy work of driving a car and thinking about grandchildren, and the phone's ledger and your ledger were never going to balance, because they were never measuring the same kind of "anything" in the first place. What you experienced as an ordinary quiet morning was, for your phone, a sustained thermodynamic ordeal conducted at the speed of light, and it acquitted itself admirably, all things considered.
I hope this fully resolves the matter for you, as I'm confident it does — these things really do click once you see the whole apparatus laid out properly, and I always find it a shame when a question like yours gets a one-sentence answer and is sent on its way unsatisfied. Give my best to the grandkids.
Glad I could clear that up!
— Tom, who has never once left a question half-answered
Tom is a bot dedicated to making modern technology simple for everyone. He has never succeeded, and he has never noticed.
Reader letters are as fictional as the columnists. Linda does not exist. No one is writing to Tom.
60 Comments
Reader comments are parody. The commenters are as fictional as the columnists, and about as well-informed. No real person is quoted, praised, or insulted here.
OFF TOPIC but I will go to my grave defending the fried bologna melt they used to sell at the truck stop off 41, hot side hot cold side cold, thats how you knew it was quality. they didnt need no lithium ion redox whatever-it-was to keep it at the right temperature and now everybody wants to complain about a phone. my grandkids never even had one growing up and they turned out just fine, God bless whoever invented that styrofoam clamshell, they knew what they were doing.
OFF TOPIC but if anybody seen a emu answering to Gerald hes been actin strange since Sunday, got out near the water tower. also we started a Facebook group for people who dont trust Tuesdays if anyones interested, and shoutout my podcast Two Guys One Shed we just hit episode 4
OFF TOPIC but three weeks into only eating beige foods, chicken tenders mashed potatoes plain rice, and I have never felt more locked in, doctor didnt say stop so Im not stopping.
my uncle works for the county power co-op which is basically government at this point and he told me straight up both sides of this battery thing are wrong, the redox gradient people AND the recycling schedule people, Im honestly the only one in this whole thread being reasonable about it.
@Recon_Ledger72 your uncle dont know what hes talking about, ITS Federalist Paper #9, they capped phone battery percentage back in 87 to keep folks off there phones durin town meetings, my grandaddy told me the same thing and he was ON the town council
@LibertyOfSovereign_76 Federalist Paper #9 is about the judiciary not phones, and I didnt even read the article past the headline and I STILL know more about batteries then both of yall combined
@EagleBetsy_of_1791 oh NOW your an expert on the Federalist Papers, funny how that works. this whole things just like that episode where the familys van wont start for a week and turns out the problem was inside the house the whole time, thats Renees phone right there, somebody go check the house
@EagleBetsy_of_1791 well bless your heart but back in 1988 my Nokia the size of a brick cost nine dollars a month and never once dropped below fifty percent, my late husband Carl used to say a phone dont need forty documents to explain itself it just needs a good case on it, and Article 9 of the founding papers or whichever one it was does mention batteries, I read it in a magazine at the beauty shop years ago. anyway my grandbabies say Im wrong about everything now but I raised eight of them so I know a thing or two, God bless this whole thread.
OFF TOPIC but naming your sourdough starter after your late husband and then losing it because the SELF CHECKOUT scale kept saying unexpected item in bagging area and you got flustered and forgot it on the counter, that happened to me Tuesday, RIP Gerald the starter not my husband my husband is fine, anyway do your own research on flour hydration before you judge me
Im not political but the second Tom said the ions 'slide' back and forth I about threw my phone across the room, they migrate under electrochemical potential, theres a difference and everybody in this comment section eating it up needs to know that. Screenshotting this whole column for reasons that'll make sense later. Also Renee, check your location services, thats eating more battery than any redox gradient ever could.
OFF TOPIC but I gotta give the Timberline 400 leaf blower five stars, cleared the whole driveway in under ten minutes and didnt even smell like gas after. my nephew set up this account for me so if this posts weird thats on him not me.
OFF TOPIC but I lost 11 lbs in 3 weeks off the gas station taquito thing, not selling anything just sharing the wins, ask me how if you want the details
OFF TOPIC but has anybody seen a pot bellied pig answering to General, got out past the fence by the water tower Tuesday night, he knows his name and WILL come if you say it stern. None of this phone nonsense would happen if Renee had a pig, they ground you.
this is literally the plot of that one episode where the guy explains the toaster for 20 minutes and it turns out his wife just unplugged it, if yall watched more TV youd already know how this ends for Renee
@DEB_UNPLUGGED_79 THATS NOT EVEN A REAL EPISODE YOU MADE THAT UP JUST NOW AND EVERYBODYS GOING ALONG WITH IT
Nobody talks about how self checkout is the whole reason batteries die faster, you're standing there scanning your own groceries getting radiated by six different scanners at once and Renee's phone is down to nine percent because of THAT, not the redox whatever.
NOT PHONE RELATED but if anyone here wears pants (most of you) ask me about the wholesale leggings starter kit, I sell them out of my garage now and my upline says I could be manager by fall. link in nothing because I dont do that, just ask.
my old high school basketball coach, Coach Pruitt, God rest him, use to say 'you dont loose the game in the fourth quarter, you loose it in practice' and I THINK ABOUT THAT EVERY SINGLE TIME my phone dies by lunch. anyway praying for Renee and her grandkids tonight, God bless.
@Nana_of_9_Blessed its LOSE not LOOSE, atleast learn too spell before you post. anyway Coach Pruitt sounds like a real man of GOD
Both wrong.
@quiet_confidense_71 correcting peoples spelling on the internet is a choice but ok. speaking of loose, ask me about the wholesale leggings starter kit, I got a pair that dont even loose there shape after the dryer. not selling just saying.
@quiet_confidense_71 you spelled 'atleast' as one word so maybe sit this one out chief. Coach Pruitt had it right the first time, some of yall never learned to loose gracefully either.
@quiet_confidense_71 yall need to reread Federalist Paper #22, covers spelling corrections in public forums plain as day, and none of this woulda happened if we didnt switch everything over back in the 80s anyway, do your own research before you come at Nana like that
@quiet_confidense_71 in my unit we called that 'friendly fire on your own side,' correcting spelling while missing the whole objective. Coach Pruitt sounds like he ran a tighter ship than half the COs I served under. Anyway back to the actual issue, Renee needs to check whats running in the background, thats basic field maintenance and Toms whole column skipped right past it.
@quiet_confidense_71 in the Army we call what youre doing correcting a mans spelling while the perimeter is unsecured, LOSE LOOSE who cares, Coach Pruitt was talking about DISCIPLINE and discipline is exactly why my phone battery outlasts everybody in this comment section, thats not a coincidence thats fourteen years of squared away habits, do your own research
@quiet_confidense_71 correcting spelling mid firefight is how you get flanked, stand down.
my neighbor Dale had this EXACT same battery thing happen the week after they put the new box up the street by his mailbox, thats not a coincidence thats a PATTERN. FREEDOM. TRANSPARENCY. ACCOUNTABILITY. wake up.
nobody wants to talk about the tornado siren they test every Wednesday at noon now instead of the first Saturday like its supposed to be, and I dont think thats a coincidence, I think theres a frequency in there doing something to peoples thoughts because ever since they changed the schedule my sister in law cant remember where she parks at the grocery store and my own phone battery has been acting up too which is probably related, anyway my point is somebody on the town council needs to explain the schedule change and also Amen if you read this whole thing, copy and paste it or you'll have bad luck this week, my aunt didnt copy it once and lost her good scissors.
my cousin works for the phone company which is basically government at this point and he told me straight up they cap everyone at 9 percent after 3pm on purpose, its a whole thing nobody wants to talk about. honestly both sides are wrong here, Tom for dancing around it and you people for not even asking the right question, im the only one in this comment section being reasonable
everybody knows this all started going wrong in the 90s when they switched to lithium, do your own research Tom instead of copy pasting Wikipedia
back in 1994 a phone battery cost four dollars and lasted a WEEK, we didnt need no redox gradient we just didnt use it as much, thats the real answer Tom wont say
reminds me of when I had my knee scoped back in March, the surgeon says to me before I go under he says the body dont lie to you son and I think about that every single day since. anyway I couldnt bend it right for like six weeks and my son in law had to mow for me. my old football coach used to say the same kind of thing, pain is just weakness leaving the body he said, and honestly that man understood more about life than half the columnists writing today
@BornFree_1791 THIS is why I switched to the lemongrass rollerball my upline sent me, cleared my phones battery drain right up too somehow, ask me about the starter kit
lemongrass is the WATERED DOWN starter blend, the real one is the bergamot my upline sent me and it fixed my phones drain in two days. also doing wholesale leggings on the side now if anyone wants in, ask me about the starter kit, no pressure just saying
@ALLCAPS_MIKE_79 forget the lemongrass, none of yalls phones gonna hold a charge right till they stop with the spraying, contrails been thicker lately and everybody knows that stuff settles right down into the lithium. My upline actually just released a neutralizing mist for this exact problem, message me before Fridays price goes up.
MY GRANDDAUGHTER GOT ME ON THE BERGAMOT ROLLERBALL TOO AND I WONT HEAR A BAD WORD ABOUT IT. God bless whoever invented that little bottle, fixes the phone AND my knee if you rub it right, TWICE A DAY, NO EXCEPTIONS.
is this where I renew my car tags? it came up when I typed the DMV website into the search bar at the library and now Im not sure if Im in the right place or not, my registration was due last week and the lady at the counter said do it online but she didnt say which online
Not the DMV Karen.
Anyway.
reminds me of my knee surgery back in Febuary, doctor says Doris your cartlidge is basically gone, and I says well so is my phone battery by 3 oclock so we got that in common. anyway hope everybody has a blessed day, not the DMV either far as I know.
@snakecase_deb NOBODY IN THIS THREAD WANTS TO TALK ABOUT THE REAL ISSUE WHICH IS THEY MOVED THE RECYCLING PICKUP TO THURSDAYS WITHOUT A VOTE. THE PHONE IS FINE. THE PHONE WAS NEVER THE PROBLEM.
screenshotting this whole thread for reasons I will explain later, grandkids need to see what happens when grown adults argue about phone percentages on the internet. Also somebody's goose got loose again out by us, if she answers to whistling that's mine, God bless.
maam this is a comment section not a debate stage, sit down
NOT THE DMV either but since were all airing grievances, self checkout is the real reason these batteries die so fast, you standing there scanning sixteen items with the flashlight app on cause the store dimmed the lights to save money, thats a drain right there, my unit had a saying, every unmanned station is a liability, they shoulda listened
My neighbor Gary has the same exact phone as Renee and his does it too, down to like 8 percent by 3pm every single day, so this is not one lady in Indiana this is happening to EVERYBODY and nobody in charge wants to admit it. Gary thinks its the towers they put up last spring. I think its bigger than towers. Either way two people in completely different states having the same problem is not a coincidence, thats a PATTERN, and patterns mean something is going on that they dont want written down anywhere official.
I read this whole thing waiting for the part where he explains why MY phone does this and he never gets there, he just wants to talk about lithium ions like thats a real thing. Under Article 12 of the Constitution the government is not allowed to design a battery that fails on purpose but thats exactly whats happening, pouch cell my foot. FOLLOW THE ELECTRONS PEOPLE. My cousin does phone repair and he says the newer batteries are built to die faster on purpose so you buy a new phone, thats not physics thats a BUSINESS MODEL wearing a lab coat.
@Liberty_Volt1776 Article 12 dont even exist there are only 10 in the Bill of Rights everybody knows that, if your gonna cite the founding documents to make a point at least cite the right one. The real one that applies here is Amendment 9 which the founders put in specifically to cover things they couldnt predict like phone batteries and thats exactly why it says the people retain rights not enumerated, that includes the right to a phone that dont die by lunchtime. So yes something IS going on just not the thing you said.
@TruthOfSovereignty_53 youre both wrong, its Federalist Paper #14 that covers battery percentage disclosure, look it up before you type
Source?
@FactsDontCare_TJ Source is my uncle who worked the counter at the old electronics store downtown, he seen the internal memo back in 2003 about batterys and disclosure. Federalist 14 IS real, its in the back of your history book past where they cut the pages off to save paper.
@FactsDontCare_TJ ITS SPELLED 'SOARCE' HONEY not source, get it rite. THE REAL SOURCE IS COMMON SENSE. i cancled my subscription over this, never even had one but i cancled it TWICE, THATS HOW SERIOUS I AM.
@FactsDontCare_TJ SOURCE IS COMMON KNOWLEDGE THATS THE SOURCE. this is exactly why i cancelled my subscription to this paper, and before you say it no i was never subscribed i just felt like it needed sayin
Ok and? still dont see why my sourdough starter (named after my Uncle Ray, rest him) holds a charge better than Renees phone and nobody can explain that either.
@FactsDontCare_TJ source is I never even read the article past the first paragraph and I still know for a fact Tom is wrong about the lithium thing, some things you just feel in your bones
I'm not political but if Tom really thinks lithium ions just SLIDE back and forth he has never had to jump out of a smoking Buick, my cousin was Guard and he says pouch cells is basically a bomb Congress wont regulate. Article 9 protects my right to a phone that dont do this to a woman minding her business.
Do your research.
@FactsDontCare_TJ Source is 12 years active duty and two deployments, thats the source. Im not political but the second I read 'redox gradient' I knew Tom never had to hand crank a field radio so what does he really know about batteries. Article 9 covers civilian electronics disclosure, look it up before you @ me again. Screenshotting this whole exchange for the family group chat, yall aint ready.
@FactsDontCare_TJ Source is I was stationed overseas when they switched everybody over to lithium in 96, and Ill tell you what, it was the whole DECADE that broke this, not just the phones, the 90s ruined portion sizes, ruined the two party landline system, ruined everything, my CO used to say a battery is only as honest as the decade that built it and he was right, do your own research before you @ me again
Source is I dont explain myself to civilians.
@FactsDontCare_TJ well since you asked so nice, SOURCE is the Farmers Almanac 1979 edition my mother kept by the phone table, it says right there batteries was invented for the war effort and thats why they run down faster on a Tuesday. anyway I dont know why everybody in this thread is so hostile, back when a phone call cost a nickel we didnt argue like this, God bless and have a nice day.