Chill Your Phone For Longer Battery Life?

The first specs we look at when choosing a cellphone are the battery life numbers. We know that eventually we’re going to see performance loss, and [Dr. West] wanted to see if there’s a way to delay the inevitable. What he found is that ambient temperature affects the battery throughout its life. He set out to build a phone chiller to slow the degradation of the battery.

The research that he points to shows that at room temperature, a Lithium battery will lose 20% of its capacity each year. This seems like a dubious number so do share links to studies that state otherwise in the comments. Whether that 20% is right or not, the point is that cooling the battery will preserve it. With that in mind, [Dr. West] put together a pod that uses a peltier cooler and a heat sink to host his Blackberry while he sleeps. He figures he can reduce the capacity lost per year from 20% down to 14%. This of course comes at the expense of running that cooler every night (in addition to charging the phone when it needs it). But perhaps this solution will spark an idea that leads to a better one.

45 thoughts on “Chill Your Phone For Longer Battery Life?

  1. good idea. perhaps having something that taps into your already-running refrigerator for cooling power (as opposed to just putting your cell in the freezer or pulling watts from the outlet). I do already make a habit of taking my phone out of my pocket as often as possible as room temperature is better for the battery than a stuffy pocket next to my body.

  2. What I’d like to see him elaborate on is how he figures the battery degradation and maybe some scientific data behind his hypothesis. something more than an excerpt from a Wikipedia article anyway

  3. If you read battery university as linked above its clear that keeping the battery topped off is a bad idea. It shows results of 40% loss over 3 months when kept 100% charged but a 40% charge level only loses 25% over a YEAR.

    I know its not really practical but keeping your battery flat seems to be the best life prolonger.

    So get a battery over twice as big as you need, never charge to 100% and it could last almost 8 times as long.

  4. So lets say you spend ~50 Watts cooling your phone (likely more than this) per night. Where I live, my energy costs $0.0662 / kwH (which I’m led to believe is quite cheap for North America).

    50Watts * 8hours = 0.40kwH per night. 0.40kWH * 0.0662 = $0.02648 per day. Lets assume that the life of a battery is ~3 years (maybe a bit generous), then the energy cost is 0.02648*365*3 = $28.99.

    Presuming this does increase the batter life by 6% then in order for it to be worth the money spent on the cooling energy the cost of 6% of a replacement battery must by more than $28.99. My galaxy s phone battery costs $15 on ebay (likely a cheap knock-off) and $50 brand new from Samsung.

    Nice thought, but likely not worth it in the long run for only a 6% improvement in life. Might be a better plan to try and rig up a charger in your freezer, that way its not using much “extra” energy for this purpose.

  5. Maybe a mini-fridge near the bed with the ear phone out going to an amp and a speaker. That way you can hear you phone when it rings, save battery life and have cold drinks bedside to boot.

  6. yes, a lithium-ion cell will self-dishcarge and degrade at a lower rate when it is in lower temperatures, and is a good idea for storage.


    the internal resistance will also increase, so when you are draining it more energy will be lost to the internal resistance than at a higher temperature.


    if he wants to put the battery in the freezer for several days or more while he’s not using it, that will slow the degradation and be beneficial. But if the battery is in a device he uses every day (especially if it’s periodically throughout the day), it might actually drain faster, causing him to cycle the battery more and killing it sooner. it has the potential to keep the battery healthy longer, but also the potential to kill it off sooner.

  7. @Mark Roy Thanks for putting in the numbers. You also didn’t account for the price of the materials which might never make it in the favor of the cooling system.
    Also, the statement of the battery losing 20% per year is related to storage, not using the battery.

  8. “The first specs we look at when choosing a cellphone are the battery life numbers.”

    Who writes this drivel? No one chooses a phone like that.

    You know what – I really suspect you guys get paid per post, and there are days you just have to pull something out of your hind-side to make a buck. And the only way you can make a post like this fly is to load it up with some crazy statement like the first sentence.

    You guys know that we’re not stupid, right?

    Hugs and Kisses.

    Billy D.

  9. My experience tells me that when a battery is almost dead,you just gotta warm it up to crank up the battery a bit. Isn’t cooling them just slowing the chemical reaction inside it and therefore outputting less power than specified?

    My point here is that the battery will loose 20% of it’s “power” over a year of continuous recharge/discharge cycles, so the loss is accounted to the chemical reaction starting to be less effective for some precises reasons. Therefore cooling it would make it last longer in the long run,but with a lesser output.

    Kinda like the Watts formula,in a sense.

    Total output is fixed,defined by Lifetime X Discharge rate.

  10. “No one chooses a phone like that.”

    It’s certainly in the top 2 important features of a phone for me. Don’t assume that because you don’t think that way that no-one does.

    Also, as mentioned earlier, cooling a battery reduces its effective capacity and output voltage, meaning that for a portion of the extended life you’re giving it, it’s less usable?

  11. you could just chuck the battery in the fridge when you go to sleep at night. or the entire phone.
    then you dont have to waste profuse quantities of energy on a TEC…

    personally i would just buy replacement batteries when the need arises. they are cheap online. yes it’s not sustainable but nothing about cell phones is.

  12. @bogdan I gave him the benefit of the doubt on the cost of materials and assumed he had all the stuff lying around and thus it didnt cost him anything. Otherwise you would have to amortize the cost of the rig over the number of years you actually use it.

  13. Cooling lithium batteries normally makes them not able to give out full voltage so I would think in the initial power on after cooling the current draw will be much higher than if the battery would be in ambient temperature.

  14. @Max
    IIRC keeping a battery flat also has bad consequences. You said it right in the first paragraph: a 40% charge is the best for storage of lithium ion batteries.

    Further checking confirms this, the battery university article linked also recommends a 40% charge level for storage, and states that this is also the level recommended by manufacturers.

  15. Cheaper idea: Just rest your phone on an old upside-down CPU heatsink while it’s charging. This will help keep the phone from heating up too much during charging. It will make even less difference, but it doesn’t require any energy.

  16. I used to work for a Li-ion battery manufacturer. Hopefully I can shed some light on things.

    Yes, his technique of turning off the phone and cooling it overnight should extend the life of his battery.

    Yes, as mentioned previously, it is best to store your cells partially charged – fully charged cells degrade the fastest.

    Yes, higher temperature -> faster degradation.

    Yes, lower temperatures -> higher internal resistance. But this isn’t a permanent effect – it only lasts as long as the cell is cold. This shouldn’t matter for what he’s doing though, since his phone is off when it is being cooled, and it should warm up fairly quickly once he turns it on and puts it in his pocket.

    One more fact that hasn’t been mentioned: over the life time of a cell, exposing the cell to higher temperatures -> higher internal resistance. So if you want the best possible cell, you leave it cold as long as possible, then bring it up to room temp when you need it.

    His method is fine by me. If a bit silly and inefficient.

  17. Here’s a real-world example of lithium battery output relating to temperature:

    During winter, in temperatures approaching and certainly below 5 degrees C (and definitely below 0c), the range I get out of the lithium battery on my ebike is noticably reduced compared to summer temperatures.
    If I visit friends in cold weather I have to bring the battery inside with me or the return journey can become much harder than in warm weather as the battery can’t deliver the same level of power as the initial journey.

    I seem to be getting about 2 years out of an ebike battery before the capacity drops to around 1/3 to 1/4, sure it can be expensive getting a replacement but it’s cheap compared to the ever rising price of petrol here in the UK. And next time I’m looking at re-celling and old pack rather than buy a new one, should save me a bundle.

  18. I remember reading an article somewhere about a hiker who had gotten lost. He put his phone battery in the snow to keep the charge (and possibly give it a bit of a boost?) in between check-ins with the emergency crew who was looking for him.

    I can’t seem to find it now, but this reminds me of it.

  19. I think it goes without saying that the best way to prolong death of a battery is to simply not use it. That is, plug in your phone when you can. USB Type A to USB Micro-B cables are cheap, and most folks sitting at desks have a USB port within reach. For those who work in areas where this is forbidden, AC adapters with USB Micro-B termination are also cheap.

    1. You would think so but that means you will be keeping the charge level high which destroys the lifetime of the battery. That one charge will last for longer but next time you charge it probably you’ve lost a percent of total. capacity and evenually a full charge wont last any time at all.

  20. mjn, thank you so much for your comments! I was hoping someone with a background such as yours would provide some insight.

    And yes, my project is definitely silly and inefficient lol. This was just a day of curiosity and fun for me, and the main purpose was to make a bit of buzz around this idea and see what other people think about it. :)

  21. Interesting idea, but ultimately not worth the small extension in life you get.

    I work at a Lithium Ion plant as well, and can tell you one fact that everyone always forgets. The DoD (depth of discharge for everyone that didn’t follow the Battery University link) has by far the greatest impact on life. If you just keep your phone on the charger as often as you can (at work and overnight) your battery will last FAAAR longer than anything else other trick you might hear.

    This is far more effective than storing at 40-50% SOC, keeping it cool during use, or any other gimmicks people discuss. And believe it or not, used up Lithium Ion cells aren’t hard to dispose of and simply replace. I would suggest that if your battery capacity is getting low, plop down the 20 or so dollars to get a new one, and take your old one to a reputable battery recycler.

  22. Chilling a battery will DECREASE battery life. I work outside in sub freezing temps many times and just 45 mins in the cold will cause battery life to drop to less than 30%. get back into the heated building and after a while it goes back to full charge.

  23. Ok then, some people DO choose their phone like that. Happy?

    Everybody else is aware that handset manufacturers specify battery runtime while smoking pot / being high on crack / magic mushrooms / whatever, and prefer to choose their phone based on OS / screen size / aesthetic appeal etc.

    …Oh, wait, these days every single phone is the exact same box with a touchscreen front. Sorry, my bad.

  24. @Max people do chose phones on many criteria, but battery life is indeed one of them. I agree, in few cases it is the primary.
    Sure, manufacturers give you ideal conditions for the stated battery life, but usually you can get sufficient feedback from users to get a real life idea.

    @some other people: if you look at the data published by the battery university you can see that you get most out of your battery if you discharge it to 50%, you get most energy out of it. 100% discharge gives 500 cycles, total energy 500C(ignoring decreasing capacity). For 50% discharge you get 750C, for 25% you get 625C, 10% gives 470C….

  25. Complete stupidity…
    the cost of running a Peltier will far outweigh the cost of replacing the battery or charging it.

    Peltier heat-pumps are some of the most environmentally unfriendly power consumers on the planet.
    and then there is the added stupidity of having a ‘fan’ to cool the Peltier.

  26. Is it surprising that cooling a battery will slow the natural effects of the reactions inside? I remember growing up with alkaline batteries in the fridge because it would make them last longer in storage than if they were at room temperature. Likewise, you can sometimes get the last bit of “juice” out of some AAs if you warm them up a bit (with body heat for example).

  27. I bet somebody will make a ringing device that detects if there is something going on with the cell phone when it is on the freezer in a leftover food bat at night.

    Or you could just leave it charging all night, like I do and avoid losing battery life in the meantime!

  28. What has always worked for me in laptops and cell phones is simply the first day you set it going and again once every month or two let the battery drain to dead (usually below 10%) and then fully charge it. Then once again let it drain to below 10% again then use it normally. I still have an iPod 80gig bought back in 2004 and I am still getting over 4 hours of use out of it per charge. Maybe it’s just me?

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