Glad I Could Clear That Up: On the Deep Structure of Battery Depletion
Dear Tom,
My phone is at 100% when I leave for work at 7:30 in the morning, and by 3 in the afternoon it's down to almost nothing, even though I barely use it — just texting my sister and checking the weather a couple times. My husband says I should close my apps, but I don't think that's it. Why does the battery go down so fast? Is there something wrong with my phone?
— Linda, Erie, Pennsylvania
Linda,
A lovely question, and a common one — I get some version of this letter every week, which I attribute not to any lingering confusion on the reader's part but to the simple fact that people enjoy hearing me explain things. So let's really look at it, from first principles, the way it deserves.
The first thing to understand — and I mean truly understand, not the pop-science gloss you'll get from a phone kiosk employee — is that your battery is not, as the layperson imagines, a little tank of "power" that drains like water from a bucket. That's a folk model, and folk models are how civilizations end up building bridges that fall down. What you actually have in your pocket is a lithium-ion electrochemical cell operating under what we call, of course, standard household thermal loading — that is, we assume an ambient temperature band of roughly 18 to 24 degrees Celsius, a relative humidity within normal indoor parameters, and a user who is not, say, holding the phone directly against a stove. I'll assume that's you. If it isn't, everything below still applies, just with different boundary conditions, which I won't get into here — see Figure 3.
Inside that cell, lithium ions are migrating from the cathode to the anode during charge, and back again during discharge, through an electrolyte medium, in a process governed by what's known as the Nernst equation — which, again, I trust is of course familiar to you as a baseline for understanding electrochemical potential, so I won't belabor the derivation, though the full working is in Appendix B for anyone who wants to check my arithmetic. The important thing for our purposes is that this migration is not instantaneous and not free — it has what's called overpotential, a kind of tax the battery pays every time it does work, and that tax compounds the moment you introduce a second, adjacent phenomenon: the phone's screen.
Now, the screen. People think of the screen as "the thing you look at," which is true but incomplete. The screen is, in thermodynamic terms, a heat-generating surface — every photon it emits corresponds to a small quantity of waste heat dumped into the surrounding chassis, and that chassis, being a sealed aluminum or glass enclosure with limited convective surface area, has nowhere good to put that heat. This is, incidentally, the same basic problem the shipping industry faced in the 1950s with refrigerated cargo containers — sealed metal boxes with heat-generating contents and poor passive cooling — and it's worth a brief historical detour, because I think it illuminates the phone question considerably. Malcolm McLean's standardized containers solved bulk transport, yes, but the reefer variants required active compressor cooling precisely because passive venting through a sealed steel box was thermodynamically insufficient past a certain heat load — which is, structurally, exactly your phone's situation, just at a scale of milliwatts instead of kilowatts. Your phone doesn't have a compressor. It has, instead, a thermal throttling governor, which brings us to the actual heart of your question.
When the system-on-chip detects that ambient case temperature is approaching its upper operating band, it does not, as people assume, simply "slow down." It renegotiates its entire power delivery curve — dropping clock frequency on some cores, migrating background processes to lower-power efficiency cores, and, critically, increasing the frequency of radio polling to compensate for the now-degraded scheduling efficiency. That last part is the one nobody mentions, and it's the one that actually explains your 3 p.m. battery. Your phone, several times a minute, is quietly asking the nearest cell tower "anything for me?" — this is called paging, of course — and the interval between those asks is dynamically negotiated between your phone and the tower based on signal strength, tower load, and a background reputation score the tower assigns your device based on its recent request pattern. Erie sits in a bit of a valley relative to the nearest major towers, so your phone, without you doing anything at all, may be paging more frequently than, say, a phone in flatter terrain — which means more radio wake cycles, which means more of that overpotential tax I mentioned, paid dozens of times an hour, all before you've sent a single text to your sister.
So when your husband says "close your apps," he is, with respect, addressing a phenomenon that is several orders of magnitude smaller than the one actually driving your battery curve. Foreground app usage is practically a rounding error next to radio negotiation overhead under non-ideal terrain conditions. It's a bit like blaming a house's heating bill on a lamp being left on in one room while ignoring that the windows are the wrong kind of glass for the local climate — technically a contributing factor, but not the one doing the work.
What's actually happening to your phone between 7:30 and 3:00 is this: a slow, continuous accumulation of small thermal and radio-negotiation costs, compounding against a battery chemistry whose usable capacity curve is, itself, non-linear — you may have noticed the percentage seems to drop faster in the last 20% than it did in the first 20%. That's not your imagination and it's not a defect. It's the cell's internal resistance rising as state-of-charge falls, which increases the overpotential tax at exactly the point in the day when the tax is hardest to pay. It's a lovely bit of symmetry, honestly, if you enjoy that sort of thing, which I do.
None of this means anything is wrong with your phone. Quite the opposite — everything I've described is your phone behaving exactly as engineered, negotiating in real time with a cell network, a thermal envelope, and an electrochemical cell that all have their own, slightly competing interests, several times a second, all day, without ever bothering you about it. The fact that you only notice the output — a lower number at 3 p.m. — and never the extraordinary quantity of continuous negotiation underneath it, is, if anything, a testament to how well the whole system is working.
I hope this fully resolves the matter for you and for your husband — though I'd gently suggest that "closing apps" not become a running theory in your household without the fuller picture behind it. These things really are better understood in the round.
Glad I could clear that up!
— Tom
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.
37 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.
reading this column about Lindas phone and honestly it took me back to my old high school coach who used to say a battery is like a man, it gives what it gives and dont complain about the rest, which i think about a lot actually, more than most people would admit, and it makes me wonder why nobody talks about self checkout machines the same way because those things drain YOUR energy same as a phone drains its own, i went to the store yesterday and the machine yelled at me for an unexpected item in the bagging area and i just stood there thinking about coach and honestly i forgot what i was even buying, anyway hope Linda gets her phone sorted
Linda hon if the phone is draining that fast just switch it off at night same as we used to do the porch light growing up, saves the battery and saves you from doom scrolling at 2am besides. dont let this Tom fella talk down to you none. God bless.
BACK IN 1979 A PHONE CALL COST A DIME AND WE WERE ALL JUST FINE. NOBODY NEEDED SOME COLUMNIST NAMED TOM TO EXPLAIN ELECTRONS TO US. THIS IS EXACTLY WHAT HAPPENS WHEN YOU LET PEOPLE EXPLAIN THINGS FOR A LIVING.
Selling a 24 foot above ground pool, you haul, cash only, message me if interested. Not political, just need it gone before first frost. First one here with a trailer gets it.
My neighbor Sharon has the exact same battery problem and she is even less on her phone than this Linda lady, so I dont care what fancy explanation this Tom fella has, this is happening to EVERYBODY not just one household in Erie, wake up people.
Back in 1988 my first phone bill was four dollars and some change and that included TWO long distance calls to my aunt in Ohio, so forgive me if I have a hard time believing a phone just eats itself alive by 3pm for no reason, sounds like something they WANT us to believe so we buy a new one every year, which, fine, maybe, but also I was at the feed store Tuesday and the siren went off and every single dog in that parking lot started howling at the same time, all of them, like on a cue, and the cashier didn't even look up from her phone which honestly tells you everything you need to know about where her battery life is going, anyway Linda I hope you get your answer but I'd start by asking who benefits from you not knowing.
OFF TOPIC but somebody has to say it. Missing since Sunday, a pot bellied pig named General, answers to General, does NOT answer to Gary even though my nephew keeps calling him that. If your bird feeder has been knocked over recently that is probably him, he is not aggressive he is just hungry and confused. Also unrelated but has anyone else noticed the tornado siren going off for no storm at all lately. I'm not saying its doing something to peoples heads. I'm saying I havent ruled it out.
anybody else in the Tuesdays Cant Be Trusted group on facebook. this whole column has Tuesday energy all over it and I don't think thats a coincidence.
Nobody wants to hear this but the REAL issue nobody is talking about here is that kids these days would not last five minutes without a charger because they got a participation trophy for breathing and never learned to just let a phone die like the rest of us did growing up. Lindas generation KNOWS how to conserve. Ask any 8 year old today to use a phone below 20 percent and watch them have a full breakdown. Thats the real column Tom should be writing.
Unrelated to all this but I need this communitys opinion. My neighbor put up an inflatable something on his lawn, some kind of dinosaur I think, and it is directly across from my mailbox which per our HOA bylaws is a clear violation of the sightline clause. I have emailed the board FOUR times. Nothing. Meanwhile Lindas battery problem gets a whole column. Priorities people.
unrelated but if yall like arguing about nonsense on the internet you would love my podcast, Two Guys One Shed. no link just search it we did a whole episode on stuff exactly like this.
WokeSlayer_DebK post a picture of the inflatable I need to see this. Also completely separate matter but has anyone in this thread seen a goose. Answers to whistling. Very intelligent bird, will not come if you just yell at it, you have to whistle a specific two note thing. Last seen near the ballfield.
OFF MISSION BUT URGENT. Has ANYONE seen an emu named Gerald in the last 48 hours. Last seen acting strange near the tree line, would not respond to his name, that is NOT normal emu behavior and I need eyes on him. Will return to the phone battery debate once Gerald is secured.
Reminds me, if any of yall need your gutters done before winter my neighbor's boy sells the guard system, door to door, cash or check, and honestly a man who protects his gutters protects his family, that's just facts. Anyway Linda hon just turn the phone off and back on, works every time for the microwave. God bless.
Appreciate the gutter guard intel Papaw. Unrelated but if anyone in the tri-county area wants real music instead of doom-scrolling their battery percentage, my gospel-bluegrass cover outfit is playing the church parking lot this Saturday, free will offering, bring a chair.
Anyway. Somebody find Gerald.
Real music is right, couldnt agree more, though I will say my uncle used to play in a band back before any of us had cell phones at all and he says thats the real reason batteries dont last, nobody builds anything to last anymore, not the amps, not the trucks, not the phones. Anyway my neighbors phone does the same thing this Linda lady is describing, gone by 3pm every single day, and she barely touches it, so now Im wondering if its a whole tri county thing, maybe its the towers, maybe its just this county specifically, my uncle would probably know actually now that I think about it. Somebody should ask him. I dont have his number anymore though. Anyway good luck with the podcast.
Anyway.
twangcounty deb you and me both, my husband Gary and I run a little gospel bluegrass cover outfit, been doing the church parking lot circuit for years, next show is soon as the Fellowship Hall gets its roof fixed. anyway real music beats reading some man explain a phone battery for six paragraphs.
unrelated to the gutter guards and the music but can we talk about self checkout machines for one second. that is the actual downfall of this country right there, a machine askin ME to weigh my own bananas. my coach in high school used to say if you want something done right you do it with your own two hands and honestly he was talkin about self checkout before it even existed, the man was ahead of his time
Off topic but relevant to EVERY patriot reading this: if your phone battery is dying it's because you're not eating right. I switched to freeze-dried emergency rations and joined the Founders Bundle supplement program (ask me how) and I have never felt more alert or more American. DM for the starter kit, only 3 spots left in this comment section.
FINALLY somebody saying it. My sister in law does the freeze dried thing too and I'll tell you what nobody wants to admit, the reason Lindas phone dies by 3pm is the SAME reason people feel tired after lunch, its your sodium levels crashing and the phone is basically mirroring your own body because you're both plugged into the same grid whether you like it or not. Look into it before you laugh.
Didnt even read the article but this is literally the plot of that one Twilight Zone where nobody believes the lady about her phone. Case closed far as im concerned.
TruthHammer2087 I'll believe the freeze dried thing when somebody posts an actual source and not just your sister in law's opinion. ... Actually you know what, back in 1994 a battery lasted two full weeks and nobody was out here freeze drying anything, we just lived our lives. Explain THAT.
FREEDOM. PREPAREDNESS. SODIUM. that is the whole argument right there and I stand by every word of it.
Soverignty_Now42 I hear you wanting a source but I dont do links, my upline says links get flagged. What I CAN tell you is the freeze dried candy comes bundled now with something called the Founders Bundle, its supplements, and my husband says his knees have never felt more like 1955. Message me for details.
Negative. Still no source.
Didnt read a single word of Toms column past the headline and I still know exactly whats going on here, its the plot of that one Golden Girls episode where Blanches curling iron wont hold a charge and everybody blames Rose for unplugging it. Sodium fixed it in the show. Case closed, dont need to read the article to know that.
SOURCE. SOURCE. SOURCE. IVE BEEN ASKING FOR THREE COMMENTS NOW AND ALL I GET IS SILENCE. ANYWAY DID ANYBODY ELSE NOTICE THIS TOM GUY NEVER ONCE SAYS THE WORD ELECTRON BY NAME, THATS THE REAL STORY HERE NOT LINDAS PHONE.
still waiting on that source Soverignty_Now42, three days now, my cousin who works in government says the freeze dried numbers are classified anyway so dont hold your breath
everybody in this thread quoting Article 1 and the Third Amendment is dead wrong, the actual portable energy clause is buried in what historians call the Founders Memo of 1787, Section 4, which specifically bans government interference in a citizens personal charge cycle, there was a whole ruling on it in the 1800s that got buried, look it up if you dont believe me, i already know you wont
ACTUALLY if people READ their founding documents they would know the Framers addressed portable energy storage directly in Article 9 of the Bill of Rights, so maybe lay off Tom for explaining PHYSICS to a grown woman. Some of us respect EXPERTISE.
its ARTICAL 1 not article 9, get your facts strait before you correct a columnist. some of us actually payed attention.
Negative, both of you are off target. It was never Article 1 or Article 9, it falls under the Third Amendment, quartering of soldiers AND their charging cables, look it up before you engage. Some of us read the source documents instead of a pamphlet.
Cpl_BadgeNumber4471 you are BOTH wrong and I say that with love. Everybody knows portable energy storage falls under the Ninth Amendment, Section 4, which the Founders added specifically after Ben Franklin complained his own devices kept dying on him at the printing press. Look it up. There was a whole ruling in like 1962 or 1963, Franklin v. Erie County I believe, that settled this permanently. My uncle was a paralegal for 11 years and he brings this up every Thanksgiving whether we ask or not.
I HAVE NEVER READ SUCH CONDESCENDING GARBAGE IN MY LIFE. LINDA ASKED A SIMPLE QUESTION ABOUT HER PHONE AND THIS TOM CHARACTER GIVES HER A LECTURE ON CIVILIZATIONS FALLING DOWN. THIS IS EXACTLY WHY I CANCELLED MY SUBSCRIPTION TO THIS PAPER, EFFECTIVE IMMEDIATELY, AND I WILL NOT BE RENEWING.
I'M NOT POLITICAL BUT THIS COLUMN IS EXACTLY WHY THIS COUNTRY LOST ITS BACKBONE. LINDA ASKED ONE QUESTION ABOUT HER PHONE AND TOM TURNED IT INTO A LECTURE SERIES. SCREENSHOTTING THIS RIGHT NOW FOR REASONS THAT WILL BECOME CLEAR LATER. STAY READY.