Draining a smartphone battery quickly

May 22, 2017

I have two related questions about draining the battery of a smartphone, which sometimes I want to do.

First, what is the quickest way to eat a smartphone battery down to zero percent? All I can think of is to set the screen to maximum brightness and turn on the flashlight. Is downloading more costly? What about streaming a movie? (I am unwilling to play sounds through the phone in order to increase current draw.) What about recording a video?

I’m also unwilling to test any of the possibilities because lazy; I’m hoping someone here already knows the answer or can point me to it.

Second question: Does it take more current to display a white screen than a black one? Is black where all the pixels are turned off? What about white compared to 95% grey? Or white compared to blue?

Thanks for any information you can offer.

Sure, any of those things, as it will place load on the CPU, which will consume power. Is your objection to playing music just because of the noise? (could headphones solve that?)

Also, turn on GPS location, and put the phone in a metal enclosure - this will disrupt its connection to the network and it will ramp up antenna power to try to compensate.

Also, get a flashlight app that switches on your camera flash constantly.

If you have an OLED screen, then white is the most battery-hungry colour - if it’s an IPS/LCD screen, there’s not much difference, unless the backlight has area dimming, in which case a white screen will consume a little more power.

Finally, be aware that you’re not actually draining the battery to zero, because the phone won’t allow it, and if all of the above measures cause a heat dissipation problem, the phone OS may shut down some of your things to prevent it running away.

Do you mind if I ask why? I’m having a hard time coming up with a good reason to do so.

And fire up Google Maps or some other app that’s constantly asking for GPS location. While you’re at it, blast some music at full volume so the speaker is making music and the CPU is busily unpacking an MP3.

Playing a movie will do that and more.

I want to stress the heat issue that’s been mentioned. Drawing down a phone battery makes it heat up. The faster you do it the hotter it will get. Heat is the enemy of rechargeable batteries. It reduces their lifetime.

In short: Do not do this. Rethink why you want to do this and if it still makes sense go talk to some rational people who will give you a load of reality about what you have going on.

Just don’t.

If this is related to “memory effect” of rechargeable batteries, don’t waste your time. Newer rechargeables don’t suffer from memory effect the way (some) older ones did.

May 23, 2017

Mangetout and Machine_Elf, thanks for your replies.

engineer_comp_geek, it appears you’ve asked a good question, and I thank ftg and JHBoom for following up.

A couple people once told me it’s desirable every so often to run down a rechargeable battery to as close to zero percent as possible, then to recharge it fully. This might have been back in the days of flip-phones. I now sport a Samsung Galaxy S7, which is not the explodey kind.

If there is no reason to do this I will stop. Is there an authoritative site or two that tells how to care for a modern rechargeable battery? I mean questions such as these:

– Should I try to top it off whenever I do charge it? Is one full charge better than several lesser ones?

– Does it matter how low the charge gets, assuming it’s not really close to zero, before I start recharging?

– Does it hurt anything to let the battery sit on the charger after it’s hit 100%? A Verizon emplyee told me last August that it does.

– Should I stop microwaving my phone for ten minutes every month?

Also, with respect kind of to whether a light color eats battery faster than a dark color, if you go to the page at http://barelybad.com/images/Grey_square_optical_illusion.png you will two squares labeled A and B. Their background colors are exactly the same shade of grey. Hard to believe, isn’t it?


You’re referring to the memory effect, which does not affect lithium ion batteries. Repeated deep discharge of lithium ion batteries won’t do anything except shorten battery service life.

EDIT: this site has an exhaustive rundown on how to prolong battery life


Agreed, but in practice, the phone probably won’t allow a true deep cycle discharge - when you run it down, you’re running it to a lower threshold voltage that the phone describes as ‘0%’ and shuts down.

If you were to remove the battery, disable battery protection circuitry and attach a simple resistive load (say, a lamp) to the battery, you’d find it has lots of power left inside - it’s just that you would find that running it until the lamp goes dark would seriously damage the battery - maybe even render it permanently unrechargeable, or one-time explodey.

It used to be the case (after memory effect, but before modern equipment) that running your devices to near (reported) flat would enable the battery voltage calibration to work better, but I think even that isn’t necessary any more.

Current(!) wisdom is, I believe: Lithium batteries like to be kept fairly well topped up, but have a finite life anyway, regardless what you actually do. Avoiding extremes of temperature is good too, if you can.


Probably not, if it’s the official manufacturer’s charger.

If you’re charging the battery off the phone and the charger is some cheap Chinesium, then they may have skimped on the overcharge control circuitry and that could be bad, or the charger could be getting hot, which could be bad,
But why would you do that? If you’re charging your battery inside the phone and it’s powered via the USB cable, don’t worry - the phone is in control.

Anything beyond Medium Rare is frowned upon by connoisseurs.

I think you misunderestimate us.

You are absolutely correct: ‘deep discharge’ isn’t the correct term – full discharge can cause the battery to explode so there is circuitry to prevent it. However, a battery only has a limited number of recharge cycles before they become unusable. Adding discharge/recharge cycles only hastens their demise.

Lithium batteries have a lifespan of around 4 years (even unused) but will degrade faster under certain conditions like high temps and carrying a full charge. A fully charged battery kept at 25C will lose up to 20% of its capacity in one year. This can be extended a little by storing them at low temps and at around 40% of full charge (important: recharge at room temp only). In practical use, however, just keep your phone fully charged and put your spares in the fridge.

Estimated recoverable capacity when storing Li-ion for one year at various temperatures. 
Elevated temperature hastens permanent capacity loss. 
Not all Li-ion systems behave the same.

Temperature	40% charge	100% charge
0°C		98%		94%
25°C		96%		80%
40°C		85%		65%
60°C		75%		60%(after 3 months)

Thanks to everyone who helped. I have read some of the Battery University site and plan to return for further edification. I will no longer drain my phone’s battery every so often, nor my tablet’s battery, which I was also doing.

And I will microwave them less.

Finally, I did assume some people reading this thread had seen the Grey Squares illusion, but I also assumed some had not, and it is extraordinary.

Smartphones are well-optimized for audio/video decoding, so this won’t do as much as you think. The CPU won’t be involved in decoding that mp3.

As I recall Pokemon GO was (is?) infamous for draining batteries quickly between its use of the GPS, active screen and general processing power needed for the game.

Some games do a amazingly great job at draining the battery.

Don’t forget the need to synchronize with an internet server. That can really tax your battery.

A similar application is any navigation app. It will drain your battery quickly. If you’re in the habit of using your smartphone for GPS navigation while driving (as I am) then I strongly encourage plugging it in to charge from the car while doing so.