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I want to buy a 2nd battery for my i9100 because the phone is getting old and I don't know if parts will be easily available a couple of years on (don't want to upgrade, I like it too much), but I've heard reports of batteries dying after being left in storage for extended periods. Is this true? Should I just switch the 2 batteries around each time to preserve their life?

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Unlike Ni-Cd and Ni-Mh batteries, Li-ion batteries primarily lose their capacity by calender time rather than by charge/discharge cycles. It's simply a fact of the chemistry. From the time the cell is assembled, it will lose capacity over time, regardless of whether it's in active use or sitting in a warehouse.

Stored unused, you're looking at up to 15-20% loss of capacity per year (pg 4, figure 5b) with the battery just sitting on a shelf. Though this is more a worst-case scenario, as the battery is being stored at 35°.

To help prevent this capacity loss, you should store the battery cold. In the paper above, storing the battery at 5° C (a few degrees warmer than an average kitchen fridge, which is ideally about 1.6° C) reduced the capacity loss rate by about half.

Putting the battery in a nice airtight bag (a small ziplock is good) is highly recommended for fridge storage to prevent unfortunate incidents relating to spills and condensation.

  • Oh boy. Is that safe? Even in a airtight bag you will condensation all over the battery, isn't that even slightly detrimental to the battery or it's contacts? – warsong Jul 3 '13 at 15:45
  • @warsong - That's why I specified a small bag. Air actually contains very little water. A litre of air (at 20° C and 1 atmosphere) with 100% relative humidity contains about 12 micrograms of water. Simply removing most of the air from the bag should keep the amount of water low enough to prevent it from doing anything like shorting the contacts. If you're feeling paranoid, you might add a packet or two of desiccant (e.g. silica gel) to the bag, which is readily scavengable from vitamin bottles and whatnot. – Compro01 Jul 3 '13 at 17:16

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