I have a Sonicare toothbrush which has Lithium-ion battery and a body hair trimmer that has a NiMH battery.

I have charged the Sonicare once or twice without ever using it, just to stop it go to 0% even though I am not completely sure if that is true. The trimmer is unboxed, for over a year now so I have never charged it and/or used it since it left the factory.

I know that the Lithium-ion are better for such conditions, but I don't know the details. Does the type of storage, temperature and such affect the battery? On what way does it really affect it? Does it matter that I have never once used the device, so is it different if I used the toothbrush to check it out a few times (like 4) while the other one just sits in a box. And should I always choose the device that has a Lithium-ion batteries over the NiMH? Should I periodically charge them if I plan on not using them? Lastly can a Lithium or NiMH the battery destroy the device just from sitting in it?

  • \$\begingroup\$ Where did you hear that Lithiums withstood long-term storage better than NiMH? Not to say that you're wrong but that's the first I've ever heard of that. I don't really have evidence comparing the two. I just know that Lithium-ion suffers more capacity degradation when stored with more charge and hotter.. I have never heard similar concerns for NiMH (but NiMH also self-discharge quite a bit faster). Personally, I would worry more about the Lithiums than the NiMH in long term storage. \$\endgroup\$ – DKNguyen Oct 21 '19 at 0:17
  • \$\begingroup\$ I was reading some posts years ago, but I cannot remember to recall this. Can you give me some more info on why Lithium-ions are worse, and how worse really, why worse? \$\endgroup\$ – appwizcpl Oct 21 '19 at 0:36
  • \$\begingroup\$ Lithium primary batteries (LiSOCl) can survive long term storage (Rated for 10 years, actual lifetime is higher than 20 years). Li-ion and Li-Polymer cannot - They lose ~10% of their charge per month. \$\endgroup\$ – Lior Bilia Oct 21 '19 at 0:41
  • \$\begingroup\$ @LiorBilia NiMH is 10% per month is NiMH, not Li-ion or Lipo. \$\endgroup\$ – DKNguyen Oct 21 '19 at 0:55
  • \$\begingroup\$ @appwizcpl I don't know why. As I said, I have never seen data for NiMH almost as if it were never an issue but it could just be due to differences in usage. It is standard to recharge NiMH occassionally though since they discharge so quickly, but I just saw someone say they saw manufacturer research that it is of no concern for NiMH, regardless of state of charge when stored. \$\endgroup\$ – DKNguyen Oct 21 '19 at 0:59

With NiMH the shelf life is basically forever, the cells themselves will lose their charge in a few weeks or months, but after being stored they can be recharged without problems. There us no wear mechanism caused by storage.

Li-ion is different, if that runs flat it gets damaged (and cannot be recharged). But if you keep it topped up it can be stored for a long time too, and it retains its charge much better thabn NiMH.

Can a NiMH battery destroy a device? I've never seen that happen, but I have seen a NiCd battery leak and damage the device. but this was during use, not during storage.

  • \$\begingroup\$ From what I read here it does seem that they lose capacity very very slowly, batteryuniversity.com/learn/article/…. At room temperatures is about 20% after a year, if the battery was at 100% Similarly I have not read this fully, but it says that at 40% charge, it will lose even less of the charge, but that might mean that as it goes lower, it loses even less percentage. I will need to read this fully to be sure though. \$\endgroup\$ – appwizcpl Oct 21 '19 at 16:11
  • \$\begingroup\$ EDIT: That is not fully true, this is a more relevant link: batteryuniversity.com/learn/article/elevating_self_discharge \$\endgroup\$ – appwizcpl Oct 22 '19 at 2:15

NiCd can be left discharged "forever" with good hope of recovery.

NimH are claimed to be recoverable after long periods without charging but my experience is that old NimH cells left for 2+ years seem to have many cells that will not accept charge. I have quite a few cells of many brands so this is not just based on a specific model or brand. If of enough interest I could dig a few out and try charging them - probably 2 to 5+ years in some cases. ~~ Time warp ~~ I just measured a few NimH AA cells which were probably fully charged around 7 or more years ago (!). They measured in the 0.5 - 0.7V range. I have not yet tried recharging them.

NimH low discharge cells - specifically sold as such, have usable shelf lives of typically 2+ years and some claim much longer. Look at Eneloops (was Sanyo, now Panasonic).

LiIon batteries have both cycle lives and calendar lives.
While calendar lives are claimed to be in the "few years" range I have some VERY old ones - probably 15 or so years old - that (I just measured several) are at 3.65V. They have never been used, but also not charged since I have had them.

SO - if a LiIon battery was charged very occasionally and never used I'd expect it could have a very long shelf life. Optimum voltage for longevity is around 3.85V (from memory).

  • \$\begingroup\$ Interesting, thanks for real life example. I have linked in the others comments a detailed post about this, I wonder if it truly matters if they are once or never charged, so that we can now if there is difference between something in an opened box or not, if there is some kind of "activation" of the battery, but probably that happens already in the facotry when tests are being done (depending on the product I guess). Oh, and form what I read here the optimal in terms of longevity is at about 3.92V. \$\endgroup\$ – appwizcpl Oct 21 '19 at 16:14
  • \$\begingroup\$ @appwizcpl LiIon always come (at least partially) charged (as otherwise they are dead). NimH also but deadness less certain. NimH will often be mostly or fully charged. Std NimH self discharge rapidly enough that they will seldom be anything like fully charged when purchased. LSD NimH are sold initially fully charged and will almost always be close to fully charged when purchased. NimH does not (notionally) have a calendar life - unlike liIon. My ~=15 year old still alivish LiIon are "interesting" \$\endgroup\$ – Russell McMahon Oct 21 '19 at 20:29
  • \$\begingroup\$ Ok, so this link has the more relevant info: batteryuniversity.com/learn/article/elevating_self_discharge I have stored a new Lithium-ion device which probably has 600 mAh battery for about 2 years without charge. And I also had a similar device that was only once fully charged and then left for 1.5 year and a half. Considering the numbers shown in the links, discharge rates can be high at given levels, but overall my batteries are probably damaged to some extent, I just not sure if it is as much as this site refers to. \$\endgroup\$ – appwizcpl Oct 22 '19 at 2:30

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