Li-Ion -- Time to lose charge when not in use?

When stored at room temperature or in an unused light, how quickly do fully charged, high quality li-ion batteries lose their charge? I presume they lose a charge much faster than eneloops do, but how much faster?

I've heard they will lose 10% of their charge after sitting idle for 30 days .

torpeau said:

When stored at room temperature or in an unused light, how quickly do fully charged, high quality li-ion batteries lose their charge? I presume they lose a charge much faster than eneloops do, but how much faster?

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Actually they don't self discharge very much at all. Here is a thread where SilverFox had a battery in storage for over a year with almost no drop in voltage. Some protection circuits may cause what appears to be self discharge. Here is another good link on Li-Ion's from BatteryUniversity. Towards the bottom of BU's page in a section called, "Hints to long battery life", they mention not to keep a Li-Ion @ 4.2 volts (fully charged) for extended periods. Apparently it causes corrosion within the cells. Li-Ion's should be stored below 3.9 volts if you're not going to use them. But of course not too low. As SilverFox mentions, the point about cell damage if stored at full charge is somewhat debatable.

I just disasembel som laptop baterres pack not in use (so not recharged) for at least 4 years. I do not know what was the V value for years ago but today it was 2.5V.
Other packs have 1 years of not in use and was at 4V (but some pair of cells was at 1.85V).
Conclusion : I can't see any actual discharge of Li-Ion in practical use.

Hello Torpeau,

I see that Al found the thread on the measured self discharge...

Keep in mind that that test was done on an unprotected cell. The protection circuit draws some from the cell, so a protected cell will have a slightly higher self discharge rate.

As you can see, Li-Ion cells have a much lower self discharge rate than even Eneloop cells do.

Tom

SilverFox said:

Hello Torpeau,

I see that Al found the thread on the measured self discharge...

Keep in mind that that test was done on an unprotected cell. The protection circuit draws some from the cell, so a protected cell will have a slightly higher self discharge rate.

Click to expand...

Excellent. Thanks for the help.

SilverFox said:

Keep in mind that that test was done on an unprotected cell. The protection circuit draws some from the cell, so a protected cell will have a slightly higher self discharge rate.

As you can see, Li-Ion cells have a much lower self discharge rate than even Eneloop cells do.

Tom

Click to expand...

How does this apply to Li-Ion battery packs, such as a portable DVD player? Should they be kept only partially charged?

Interesting comments from Gold Peak Industries (link is to pdf file) about lithium-ion.

Summary:
- Lithium Ion basically doesn't self discharge like other rechargeable batteries. Losses in unprotected cells are based on irreversible capacity loss as the cell ages.
- Protection circuitry is the most important source of self discharge.

It's a little contradictory at points within the one paragraph (no self discharge but the circuitry is the most important?!?). It doesn't seem to agree with other common knowledge. Still it seems to point to the protection circuity power usage and permanent capacity loss as the drivers of most, if not all, losses.