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I own an old iPod Classic with original lithium-ion polymer battery and I use it primarily while running. Recently I discovered that when a temperature outside is low, usually below 5 C degrees, the battery goes flat really fast and I mean 10 minutes. It doesn't matter if it is fully charged or not, it always goes down faster than when it is 10 degrees or more outside. I know that the device is 10 years old so it doesn't work as good as when it was new, but I'm curious what is the physical reason of the battery going dead faster when in cold environment. I also noticed similar behavior of my laptop battery. Any idea why is that?

Edit:

Here I found some info:

"Cold temperature increases the internal resistance and diminishes the capacity. Batteries that would provide 100 percent capacity at 27°C (80°F) will typically deliver only 50 percent at –18°C (0°F). The capacity decrease is linear with temperature. The capacity decrease is momentary and the level of decline depends on the battery chemistry."

"The performance of all battery chemistries drops drastically at low temperatures. At –20°C (–4°F) most nickel-, lead- and lithium-based batteries stop functioning."

All wikipedia can say about battery capacity is:

"The fraction of the stored charge that a battery can deliver depends on multiple factors, including battery chemistry, the rate at which the charge is delivered (current), the required terminal voltage, the storage period, ambient temperature and other factors."

It dosen't say anything about how the capacity depends on the electrolyte's internal resistance.

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  • $\begingroup$ Doesn't this say something about how the capacity depends on internal resistance: "Cold temperature increases the internal resistance and diminishes the capacity."!!?? $\endgroup$ – Hasan May 27 '14 at 9:18
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It's been a while since I studied chemistry, but if I remember correctly: the charge/discharge cycle of a rechargeable battery involves the (mainly) reversible movement of positive ions from the cathode to the anode. In order to move and generate current, the ions must be released from the anode crystal structure and incorporated in to the cathode. In your case, the ions that are moving are Li+.

I'm hypothesizing that at low temperatures, this process takes longer as the ions possess less kinetic energy. That's not to say they'll never be able to make the move, just that they take a longer time to do so at low temperatures relative to higher temperatures. The current drops as a result of this reduced flow, and can't sustain the operation of your iPod.

Essentially, the dynamic operational range of the battery is reduced - initially the process is fast enough to generate sufficient current, but it drops off more quickly at lower temperatures.

Some cool recent research on battery structures is reported here.

I'll wait for someone with more recent knowledge to correct me!

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