The AirPods have batteries 80 times smaller than an iPhone's. Why don't they charge 80 times faster?


One of the best things about the AirPods is their battery life. While most other fully wireless earbuds last 2 to 3 hours per charge, Apple's earphones promise a solid 5-hour music-listening time, and our own testing showed that as much as six hours of continuous playback can be achieved. Not bad for a gadget that uses a ridiculously tiny battery. And when the AirPods are drained, 21 minutes of charging is sufficient to top them up.

But something about this last figure doesn't seem right. The battery inside each AirPod is about 80 times smaller than the one inside the iPhone 7, so why doesn't it charge 80 times more quickly? The iPhone needs 141 minutes to go from zero to full, which makes the AirPods only about 7 times faster at charging. Well, that's because lithium-ion batteries can be quite the divas.

Lithium-ion batteries: a charging story


Lithium is well-known for being highly reactive and flammable, which makes charging a lithium-ion battery a tricky business. The process must be actively and constantly regulated in order to be both efficient and – more importantly – safe. If mishandled, a battery may suffer irreversible damage. It may go up in smoke if abused further. This is why every Li-ion-powered gadget has specialized circuitry built inside it – circuitry that limits the flow of electricity, keeping it within limits that the battery cell can handle. And what the battery cell can handle is proportional to its size.


The smaller the lithium-ion battery, the slower the rate at which it can be charged. That's because elements inside the battery (called electrodes) responsible for making electric flow possible are physically smaller, which limits the amount of electrical energy that can safely pass through them. Once again, the accent is on "safely". You surely can force a Li-ion cell to charge faster, but this can easily cause irreversible damage or even a smokey, smelly explosion. 

Of course, the AirPods are not the only product affected by this phenomenon. When I reviewed the Samsung Gear IconX wireless earphones last year, I noticed that they needed over an hour to fully charge, even though their batteries were also tiny. I'm pretty sure that smartwatches charge rather slowly primarily due to the very same reason and less due to their use of wireless charging

Just gimme the TL;DR version


What? You didn't read the whole piece? But it wasn't even that long! Anyway, what you should walk away with is that smaller batteries need to be charged at slower rates, and there's not much that can be done about it. Perhaps improvements in battery technology could make quicker charging a reality. Perhaps one day a new technology will emerge and replace Lithium-ion cells altogether. When that's going to happen, however, is anyone's guess.

iPhone 7 and AirPods teardown photos courtesy of iFixit

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17 Comments

1. Nopers unregistered

Obviously because the charging circuitry has to be shrunk down too. Stupid article.

5. zeeBomb

Posts: 2318; Member since: Aug 14, 2014

This whole article made me facepalm...

8. SupermanayrB

Posts: 1188; Member since: Mar 20, 2012

Exactly! The answer is in the title. Anything to post something about Apple.

10. trojan_horse

Posts: 5868; Member since: May 06, 2016

It's just the effects of slow day on PA, which leads to articles like this.

2. Settings

Posts: 2943; Member since: Jul 02, 2014

Coz the faster charging feature is available on the Air Pod 2. Apple's gotta make a living y'know!

3. SYSTEM_LORD

Posts: 1168; Member since: Oct 05, 2015

24mAh per pod? That's pretty efficient, if you ask me!

11. xondk

Posts: 1904; Member since: Mar 25, 2014

You'd be surprised how little power is needed to give good quality audio when using in ear headphones, especially the newer ones that are shaped a little into the ear. You'll probably find the most draining feature on them being when you use siri, playback itself can be silly low in draw.

4. maple_mak

Posts: 953; Member since: Dec 18, 2013

Because iOS more power consumption than Airpods' bluetooth and own small system... What a dump article. Airpods not powered by iOS. Clickbait confirmed.

6. phonearenarocks

Posts: 606; Member since: Mar 26, 2015

@Nick T. - Isnt that bad of an article as everyone said. Chill!, Cheers!!

7. PhoneModerate

Posts: 5; Member since: Nov 29, 2016

Because that's not how charging works?

9. marorun

Posts: 5029; Member since: Mar 30, 2015

its probably has nothing to do with cheap chips used... right?

12. chronopc

Posts: 97; Member since: Oct 18, 2012

Have you ever wondered why fat parents have fat children? Or why Chinese parents have Chinese children? It's no coincidence.

13. TechieXP1969

Posts: 14967; Member since: Sep 25, 2013

The reason it doesnt charge faster is simple. When phones are charging, they heat up. Unless you want the device to blow up, being made of plastic; you have to prevent heat. Heat trapped inside such a small part would likely catch fire. 20 mins is fast enough considering you get 6 hours. My PowerBeats 3 get up to 12hours. And they sound good too. They dont sound like organ pipes

14. Settings

Posts: 2943; Member since: Jul 02, 2014

Problem is, at that price you expect something better, something faster, something leaner. But you won't.

15. matistight

Posts: 987; Member since: May 13, 2009

If they made a 150mA charger, it'd be done in 10 minutes. If they made a 300mA charger, it'd be done in 5 minutes. If they made a 1.5A charger, it'd be done in 1 minute! The last one would turn the earbuds into Note 7's though.

16. omar98

Posts: 71; Member since: Aug 28, 2011

The title made me cringe

18. pt020

Posts: 160; Member since: Apr 08, 2014

PA you make fun of yourself... please stop it.

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