ayumi/gist:97596b2efd32c5943126

## gistfile1.txt
http://www.helifreak.com/showthread.php?t=170184

pgoelz
Rochester MI

I too have researched the subject of LiPo storage and now store my packs in a small refrigerator when not in use. I make sure they are no more than 90% charged and try to store them 50% charged when possible.

Here is what I have found:

1. Cells degrade continuously from the day they are manufactured until the day they are considered dead. Rule of thumb seems to be about 3 years to 80% capacity UNDER IDEAL CONDITIONS and probably under 0.5C to 1C discharge conditions. This is the BEST you can expect.

2. This degradation increases with temperature and with cell voltage. Stored fully charged at room temperature, you can lose 6%/yr or more IN ADDITION TO any degradation from usage.

3. Degradation is reduced to a couple percent per year by storing at lower cell voltage and/or at lower temperature but it never ceases altogether.

4. The maximum cell voltage before permanent damage occurs is 4.2V at room temperature and about 4.1V at 0 degrees C. Storage at temperatures near freezing is perfectly OK and in fact is desirable PROVIDED the voltage is less than 4.1V/cell.

In general, it seems that most degradation is expressed in terms of discharge capacity at low (for our purposes) discharge currents. It does not seem to address the increase in internal cell resistance that also occurs and which further reduces the ability of the pack to fly the model.

It has been EXTREMELY difficult to get what I would consider to be first hand information regarding long term storage. Most of the information on the web (including this post) is second hand at best, paraphrased, word of mouth, opinion, etc. I do have access to a couple cell manufacturers professionally (although not Enerland or Kokam) and I still have not been able to get good data on long term storage / cell degradation.

Paul
Paul Goelz
Rochester MI USA
http://www.pgoelz.com
	http://www.helifreak.com/showthread.php?t=170184

	pgoelz
	Rochester MI

	I too have researched the subject of LiPo storage and now store my packs in a small refrigerator when not in use. I make sure they are no more than 90% charged and try to store them 50% charged when possible.

	Here is what I have found:

	1. Cells degrade continuously from the day they are manufactured until the day they are considered dead. Rule of thumb seems to be about 3 years to 80% capacity UNDER IDEAL CONDITIONS and probably under 0.5C to 1C discharge conditions. This is the BEST you can expect.

	2. This degradation increases with temperature and with cell voltage. Stored fully charged at room temperature, you can lose 6%/yr or more IN ADDITION TO any degradation from usage.

	3. Degradation is reduced to a couple percent per year by storing at lower cell voltage and/or at lower temperature but it never ceases altogether.

	4. The maximum cell voltage before permanent damage occurs is 4.2V at room temperature and about 4.1V at 0 degrees C. Storage at temperatures near freezing is perfectly OK and in fact is desirable PROVIDED the voltage is less than 4.1V/cell.

	In general, it seems that most degradation is expressed in terms of discharge capacity at low (for our purposes) discharge currents. It does not seem to address the increase in internal cell resistance that also occurs and which further reduces the ability of the pack to fly the model.

	It has been EXTREMELY difficult to get what I would consider to be first hand information regarding long term storage. Most of the information on the web (including this post) is second hand at best, paraphrased, word of mouth, opinion, etc. I do have access to a couple cell manufacturers professionally (although not Enerland or Kokam) and I still have not been able to get good data on long term storage / cell degradation.

	Paul
	Paul Goelz
	Rochester MI USA
	http://www.pgoelz.com