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Long time reader, first time poster...

I have encountered an potential issue in regards to shipping Lithium-ion batteries in products over from China to the United Kingdom.

I have always factored in the standby battery consumption when calculating a products shelf life, but it has come to my attention that during transit in containers, these products can undergo heats of 60°C (140°F) for up to 28 days.

After this period the products will then be returned to "ambient" temperature and stored normally.

How can I factor this extreme temperature period into my calculation when calculating product shelf life?

Thanks in advance!

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    \$\begingroup\$ by standby battery consumption do you really mean "self-discharge"? \$\endgroup\$ – Steve G Aug 3 '16 at 8:01
  • \$\begingroup\$ Yes and no, due to the battery being connected to the circuit in the product it will draw a very small amount of current from the battery over time. \$\endgroup\$ – James Worrall Aug 3 '16 at 8:09
  • \$\begingroup\$ Ok, I can see that the self discharge will increase with temperature, but does the standby current increase too? \$\endgroup\$ – Steve G Aug 3 '16 at 8:14
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    \$\begingroup\$ It depends how the battery is connected into the circuit. If the battery is inside the circuit, but completely disconnected due to some type of switch, then you don't need to factor current draw from the circuit. The only way you can really calculate the minimum product shelf life would be to assume the worst case scenario of 60°C for 28 days. \$\endgroup\$ – Doodle Aug 3 '16 at 8:18
  • \$\begingroup\$ Steve - I don't believe the standby current would increase, just the self discharge as you have stated. \$\endgroup\$ – James Worrall Aug 3 '16 at 8:20
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I've found what is hopefully some relevant information over at batteryuniversity.com

Whilst I don't have any calculations it would seem that they have done some measurements of li-ion batteries

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Over the first 24 hours they will already be at 95% looking at the first table. So we can assume that they are at ~95% by the time they are put into the box ready for shipping.

Looking to the second table it would seem that they lose 35% of their charge per month if stored at 60°C whilst above 60% charge. So if we do some rounding of the time up (For ease let's just say that 28 days = 1 month). This means our 95% charged batteries lose another 35% whilst in 60°C transit. This puts our battery now at 60% charge.

So you can assume the batteries you receive to have retained >60% of their charge. I know this is all very rough estimate figures but hopefully this helps you if even just a bit.

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  • \$\begingroup\$ Well, you can't ship lithium ion batteries fully charged. I believe the standard is something like 35% now. This is to reduce the shipping hazard. \$\endgroup\$ – mkeith Aug 3 '16 at 15:47

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