My old 2008 macbook's power adapter died recently and since I was not sure if the problem was it or the battery, I ordered a new generic battery as well just to speed things up.

After I received my new adapter, I discovered that it was the problem so I continued to use the old original aging but working battery.

My question is, can I leave the new Lithium-Ion generic battery I bought in its sealed packaging until I need it? Will it degrade if left unused or should I swap them once a week to keep the new one alive...?

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    Normally, I'd say to just return the new battery and let the seller deal with storing it. Because this is a 6 year old laptop you might want to just keep it and recycle the old battery. You're probably experiencing statistically high degradation on that battery by now even if it is easy to miss because you mostly leave it plugged in. – krowe Sep 25 '14 at 10:13
  • ITM, Dude named Ben! – happy_soil Sep 25 '14 at 12:25
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    @happy_soil mac and cheese all the way my friend :) – Dude named Ben Sep 25 '14 at 20:15
  • Just to put a twist on some of what is said below, be wary of buying batteries that may have been "sitting on the shelf" for a long time. A good quality NiMH will last a year or so sitting on the shelf after coming out of the factory, but, even if the vendor recharges occasionally (which is unlikely), batteries that get several years old lose a lot of capacity, even if they don't go totally dead. – Daniel R Hicks Sep 26 '14 at 20:45
  • @happy_soil, ITM? Meaning? – Pacerier May 20 '15 at 8:00

Li-ions self-discharge, although very slowly. If you leave it for a very long time (probably many months) it could discharge so far that its "electronic fuse" will open. Once that happens, it's a paperweight.

It probably came to you with a charge in the 40 to 60% range, as that is supposedly the most stable for storage.

If you're not going to use it, I would check it every month or so. If it's dropped below about 20%, then charge it to bring it back up to 60% or so before storing it again.

If it were me, I'd switch to the new one and keep the old as a "just in case" spare. The new one should give you better runtime.

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  • This answer is more or less right but just a nitpick; it's a more of a chemical fuse. – ACD Sep 25 '14 at 13:02
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    In a way, it's both. In listings for individual cells you will sometimes see notations of "with chip" or "without chip" - the "chip" is the electronic fuse. If you get "without chip" cells you're supposed to use them in a pack that has the "fuse" circuit for the whole pack. The point at which your laptop will shut itself off is about 5% above the "fuse" point, so you can't trigger the "fuse" by ordinary operation. There IS a chemical component, but it's what makes it dangerous to recharge a low-voltage cell, and it's why the electronic fuse is there. – Jamie Hanrahan Sep 25 '14 at 16:59
  • Per this data batteryuniversity.com/learn/article/… it's also helpful to store the battery in a refrigerator to keep temperature low. – Jeff Atwood Oct 2 '14 at 20:44
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    So-called "battery university" is not a reliable source. That's not to say that everything on their site is wrong, of course. It's true that low temperatures will slow down chemical reactions, and this effect is proportional to the ratio of temperatures. The catch is that you have to use a 0-based temp scale such as Kelvin or Rankine to calculate your ratio. 40F is 94% of 70F on such scales; this won't matter much for extending shelf life. Then there is the need to avoid condensation when you want to use the cold battery. All in all, I don't think it's worth the bother. – Jamie Hanrahan Oct 3 '14 at 3:05
  • @JamieHanrahan, I don't quite understand your last comment " The new one should give you better runtime.". What do you mean by "runtime" here? Also, are you a physics or EE guy? – Pacerier Apr 11 '15 at 11:44

In my opinion - you should swap these batteries once in a month and discharge battery to 40-60% before storage.

Lithium Ion batteries "go bad" when they are stored in discharged state.

It is all about battery voltage. If voltage is too low - undesireable chemical reactions will happen and battery will degrade.

If battery is not empty and not used for long time - it will be fine. However batteries are not perfect and they slowly discharge without load. If you leave full battery for few months - it may self-discharge and when voltage drop to "almost empty voltage" - it will start degrading and loosing capacity.

If it is stored near empty state - it will degrade and loose capacity.

More about battery storage (including Li-Ion):

BU-702: How to Store Batteries (at batteryuniversity.com)

(added later: batteryuniversity.com is a website created by some company, do not consider this as 100% reliable source of scientific informations)

There are many opinions about "ideal" charge for battery storage. Some people say 40% is the best, some people say 60%. In article linked above:

Lithium-ion must be stored in a charged state, ideally 40 percent. This assures that the battery will not drop below 2.50V/cell with self-discharge and fall asleep.

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    The "Battery University" site is not considered a reliable source. en.wikipedia.org/wiki/Talk:Lithium-ion_battery/… – Jamie Hanrahan Sep 25 '14 at 19:30
  • This is not wikipedia. It's just article. I have to use scientific or 100% reliable sources on superuser.com? I can't find any better source/website with these informations in one place and... for that particular purpose - I think that article is good enough. – Kamil Sep 25 '14 at 20:04
  • FWIW, I think the added disclaimer is sufficient :) – Doktor J Sep 26 '14 at 14:39

I would cycle them. Li-Ion batteries have a shelf-life, which can be extended by keeping them at 40% charge, but they will decay no matter what. Using the batteries gets the most work out of them before they finally die.

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I don't know the answer to this in general; however, here’s a relevant incident:

Last year (2016) I found myself using a very old Tablet PC (circa 2004) and decided to buy a secondary battery for it to maybe nudge its cord-free time up past the 2 hour mark. The secondary battery was one of those which slots into a modular CD/DVD bay, (remember those?).

I found it on eBay for $20 and while unboxing the obviously time-neglected unit, I thought, "Well, here goes nothin!"

I was happily surprised to discover that it was in fine working order and could hold a solid charge!

That thing had been on a shelf somewhere, untouched for around 12 years, and it effectively doubled the battery life of my old machine.

I don't know what that means for your question, but it's another data point to pin to the board, anyway.

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I think you're probably better off using both. But most importantly don't leave a battery without use for more than a week on either a full charge or an empty charge. 70% is best.

Also best way to keep a battery long is to rarely do a full cycle (down to 0%) but use the battery on a daily basis.

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