Self discharge rate for Li-ion cells?

geepondy

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How does that compare to nimh's? I want to take my spare digital camera which takes a proprietary Li-ion cell and basically leave it in the car's glove box and am wondering how long the cell will hold a charge.
 

SilverFox

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Hello Geepondy,

Bare cells have little self discharge, however the protection circuit can draw some power and who knows what else is drawing power in the camera.

I would start out with charging after 3 months and keep track of the time it takes to charge. From there I would go to 6 months, then 12 months.

You will find that your batteries will last longer if you store them at a lower voltage than full charge. 3.8-4.0 volts would be a good range to try for. When Li-Ion cells are stored at full charge, they loose capacity and it can not be recovered. When they are stored at a lower state of charge, they still loose some capacity, but it is not as drastic. I believe the numbers suggest that 1 year of room temperature storage with a fully charge cell will see around a 20% loss in capacity, where as the same storage conditions and time at a 40% (around 3.8 volts) state of charge will only see around a 4% loss in capacity.

You also need to keep temperature in mind. If you store at high temperatures the self discharge rate goes up as does the damaged to the cell when stored at full charge.

Tom
 

jar3ds

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so when you say 'loss in capacity' are you saying the cells life in general? or only the loss of energy during the storage condition...

in other words... storing @ high charge rates will damage the battery permantely?

Thanks
 
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jar3ds said:
so when you say 'loss in capacity' are you saying the cells life in general? or only the loss of energy during the storage condition...

in other words... storing @ high charge rates will damage the battery permantely?

Thanks

Basically
 

jar3ds

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Handlobraesing,

according to your post # count (above)... you better go see that movie that comes on on tuesday :devil:
 
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SilverFox

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Hello Jar3ds,

If you have a Li-Ion cell that has 750 mAh of capacity and you store it at room temperature for one year, you can expect it to only have 600 mAh. The loss in capacity is permanent and not recoverable. It is caused by oxidation within the cell. Li-Ion cells tend to be unstable at full charge and full discharge, but work quite nicely inbetween... This information is a few years old and I believe newer cells are doing a bit better, but I don't have any data on them.

Tom
 

wquiles

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So Tom, basically, what you are saying is that cell is aging, and that as part of the normal aging process the battery will loose capacity, right?

The other point that I got from this is that if I store (or not use the cell) at a lower voltage than full charge (4.20 v) that this aging process/capacity loss is not as bad?

Will
 

Brighteyez

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Check the operating temperature range for that camera. The ambient temperature inside of a car during summer (and in your area, during winter) may be outside of the operational temperature range for the camera. Same caveat goes for MP3 players and other similar digital devices.

geepondy said:
How does that compare to nimh's? I want to take my spare digital camera which takes a proprietary Li-ion cell and basically leave it in the car's glove box and am wondering how long the cell will hold a charge.
 

SilverFox

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Hello Will,

I think we are on the same page, but let me make sure...

Let's first define that the useful life of a Li-Ion cell ends when the cell drops to 80% of its initial capacity. In normal use you may get somewhere around 300 cycles of normal use before you reach this end point, or you can fully charge your cell up and leave it on the shelf at room temperature for 1 year.

Tom
 
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