# Why does put an un-chargable laptop battery in the freezer resurrect it? **URL:** \ **Category:** Factual Questions\ **Created:** [May 7, 2012, 6:50pm UTC](https://boards.straightdope.com/t/why-does-put-an-un-chargable-laptop-battery-in-the-freezer-resurrect-it/621205 "2012-05-07T18:50:52Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Christopher\_Robin\_Davies](https://avatars.discourse-cdn.com/v4/letter/c/8dc957/32.png) [@Christopher\_Robin\_Davies](https://boards.straightdope.com/u/Christopher_Robin_Davies)\ **Post date:** [May 7, 2012, 6:50pm UTC](https://boards.straightdope.com/t/why-does-put-an-un-chargable-laptop-battery-in-the-freezer-resurrect-it/621205/1 "2012-05-07T18:50:52Z")
Over the weekend my laptop battery got to the point where it would no longer take a charge. I ordered a new one but out of curiosity decided to try something I had heard about: putting the battery in the freezer. So I put it in a plastic baggie and sealed that and placed it in the freezer for maybe half an hour, after which I let it sit the kitchen table for a while so it could come back to normal temperature. Replacing it in the laptop I found that it would now take a charge, though only for about 30 minutes worth. Why does this work? PS You do not have to bother telling me to replace the battery as I have already bought a new one. I am just curious. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [May 7, 2012, 7:09pm UTC](https://boards.straightdope.com/t/why-does-put-an-un-chargable-laptop-battery-in-the-freezer-resurrect-it/621205/2 "2012-05-07T19:09:29Z")
I haven’t studied lithium ion batteries very much, but I’m guessing that ice crystals are forming in the electrolyte (or maybe on the surface of the plates themselves) which is causing the non-conductive layer that forms on the plates to crack and chip, exposing the plates to allow charge to partially flow again. ETA: Or maybe it’s just the thermal contraction and expansion of different materials that is cracking the non-conductive layer. Just a bit of a WAG though. ---
**Author:** ![Christopher\_Robin\_Davies](https://avatars.discourse-cdn.com/v4/letter/c/8dc957/32.png) [@Christopher\_Robin\_Davies](https://boards.straightdope.com/u/Christopher_Robin_Davies)\ **Post date:** [May 7, 2012, 7:34pm UTC](https://boards.straightdope.com/t/why-does-put-an-un-chargable-laptop-battery-in-the-freezer-resurrect-it/621205/3 "2012-05-07T19:34:55Z")
> [@engineer\_comp\_geek](#): > > I haven’t studied lithium ion batteries very much, but I’m guessing that ice crystals are forming in the electrolyte (or maybe on the surface of the plates themselves) which is causing the non-conductive layer that forms on the plates to crack and chip, exposing the plates to allow charge to partially flow again. ETA: Or maybe it’s just the thermal contraction and expansion of different materials that is cracking the non-conductive layer. > > Just a bit of a WAG though. Both your explanations seemto imply that over time a non-conductive layer forms on plates within the battery and that is what causes LI batteries to become less effective over time. Is that right? If so why does it happen? ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [May 7, 2012, 9:27pm UTC](https://boards.straightdope.com/t/why-does-put-an-un-chargable-laptop-battery-in-the-freezer-resurrect-it/621205/4 "2012-05-07T21:27:42Z")
During charging, you ideally want the lithium ions to be deposited into the negative electrode. What actually happens though is some of the lithium ions are deposited on the electrode’s surface. Over time, these build up and eventually plate over the electrode, choking it and rendering it useless. The electrolyte can also decompose a bit and lose some of its ability to move ions from one electrode to the other. From a longevity point of view, these things make lithium ion batteries kinda suck, and it is why laptop batteries never last very long no matter how you treat them. This is balanced out by their relatively low cost and low weight for the amount of charge that they store, which is why we use them for laptops even though their longevity kinda sucks. ---
**Author:** ![FluffyBob](https://avatars.discourse-cdn.com/v4/letter/f/ecb155/32.png) [@FluffyBob](https://boards.straightdope.com/u/FluffyBob)\ **Post date:** [May 8, 2012, 1:42am UTC](https://boards.straightdope.com/t/why-does-put-an-un-chargable-laptop-battery-in-the-freezer-resurrect-it/621205/5 "2012-05-08T01:42:45Z")
I just wanted to add that some lithium batteries last a long time. I have a set of 3 Ah Makita cordless batteries that are going on six years and still hold an excellent charge. I am careful about letting them overheat or run down too much before charging but other than that they have given almost daily service the whole time. Laptop batteries are exposed to a lot of heat which is supposed to be very bad for lithium batteries. ---
**Author:** ![Harmonix](https://avatars.discourse-cdn.com/v4/letter/h/3ec8ea/32.png) [@Harmonix](https://boards.straightdope.com/u/Harmonix)\ **Post date:** [May 8, 2012, 1:52am UTC](https://boards.straightdope.com/t/why-does-put-an-un-chargable-laptop-battery-in-the-freezer-resurrect-it/621205/6 "2012-05-08T01:52:51Z")
Wait, does this mean if. I repeatedly freeze thaw my batteries I could theoretically break up this layer? Would it be a good idea to preventativrly do so so that a nonconductive layer has a harder time building up? ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [May 8, 2012, 7:04am UTC](https://boards.straightdope.com/t/why-does-put-an-un-chargable-laptop-battery-in-the-freezer-resurrect-it/621205/7 "2012-05-08T07:04:24Z")
You can flake/crack the buildup layer, but the accumulation of deposits near the electrode remains - additional deposits form rapidly in the new cracks. You will gain very little additional longterm benefit. Si ---
**Author:** ![obbn](https://avatars.discourse-cdn.com/v4/letter/o/d6d6ee/32.png) [@obbn](https://boards.straightdope.com/u/obbn)\ **Post date:** [May 8, 2012, 11:24am UTC](https://boards.straightdope.com/t/why-does-put-an-un-chargable-laptop-battery-in-the-freezer-resurrect-it/621205/8 "2012-05-08T11:24:58Z")
Not wanting to hijack the thread, but what is the best way to maintain a battery? Fully discharge prior to charging? Charge only for an hour or so or leave it plugged in all night? ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [May 8, 2012, 12:30pm UTC](https://boards.straightdope.com/t/why-does-put-an-un-chargable-laptop-battery-in-the-freezer-resurrect-it/621205/9 "2012-05-08T12:30:06Z")
For Lithium-Ion batteries, deep discharge is not recommended, and top-up charging is recommended ([cite](http://en.wikipedia.org/wiki/Lithium-ion_battery#Prolonging_battery_pack_life)). For laptop batteries, there is an inbuilt battery management cpu that handles the mismatches between cells and controls the charging/discharging cycle when it can. Si ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 8, 2012, 8:03pm UTC](https://boards.straightdope.com/t/why-does-put-an-un-chargable-laptop-battery-in-the-freezer-resurrect-it/621205/10 "2012-05-08T20:03:41Z")
> [@Christopher\_Robin\_Davies](#): > > So I put it in a plastic baggie and sealed that and placed it in the freezer for maybe half an hour, Just for reference, you should really evacuate the bag as much as you can, then put the bag inside another bag to minimise possible harm from water condensation. ---
**Author:** ![Christopher\_Robin\_Davies](https://avatars.discourse-cdn.com/v4/letter/c/8dc957/32.png) [@Christopher\_Robin\_Davies](https://boards.straightdope.com/u/Christopher_Robin_Davies)\ **Post date:** [May 8, 2012, 9:02pm UTC](https://boards.straightdope.com/t/why-does-put-an-un-chargable-laptop-battery-in-the-freezer-resurrect-it/621205/11 "2012-05-08T21:02:15Z")
> [@Quartz](#): > > Just for reference, you should really evacuate the bag as much as you can, then put the bag inside another bag to minimise possible harm from water condensation. Probably. I did evacuate the bag as much as I could but did not do the second part though it did occur to me after I took the battery out. It does not matter now because I have already done it and anyway I have the new battery now.