Preserving Batteries

[Pete B]

I've been too busy to finish my Frankenpad and I've managed to get 3 good batteries
in the process of buying the parts that I'd like to keep as good batteries.
I'm not using my T60 or T61 so should I charge them to 70% and put them in the
refrigerator?
What's the best way to preserve them?
Suggestions?

[brchan]

I generally store and charge my batteries to 80%. So far the original sanyo 3 year old 9 cell battery in my W530 still has 99% of the original capacity (verified through linux acpi -V command). I don't use the battery often, but I still do use it.

[theterminator93]

A little detail on how Lithium batteries deteriorate... While Li cells do lose capacity over each recharge cycle, Lithium batteries lose permanent full charge capacity over time as well, whether they are in use or not, starting the moment the cells are manufactured. The rate at which they lose this capacity is increased by temperature and charge level. E.G. a fully charged battery stored at 25C will lose about 20% of its full capacity in a year. On the other hand, a battery stored at 40% charge at 25C will lose about 4% in a year... and one stored at 40C at a full charge will lose 35% in a year. I've set charge thresholds in power manager to charge under 40% and stop charging at 70%. I fully charge the battery when I know I'm going to need the full runtime, and I always plug in the computer if there's A/C available. As a result, my original T61p 6 cell battery still holds about 70% of its brand new full charge capacity after over 200 cycles and nearly 8 years of use. That averages out to just about 4% loss per year.

If you wanted to put the battery into cold storage, just be sure you keep it above freezing and keep the charge level somewhere around 50%. You'll be good for ~2% capacity loss annually this way.

[Pete B]

Thanks, perfect!

[p.art]

http://batteryuniversity.com/learn/ - Tons of knowledge about batteries.
Quick answer: Do not heat, do not freeze your battery. Keep it charged at 85-90% when used in your laptop. Store it at 40-60% of charge.

[precip9]

http://batteryuniversity.com/learn/ - Tons of knowledge about batteries.
Quick answer: Do not heat, do not freeze your battery. Keep it charged at 85-90% when used in your laptop. Store it at 40-60% of charge.

Some of the advice has been edited to protect the general public. If you are careful, you can do better:

A simple physical fact: the higher the state of charge, the more rapid the deterioration.
Freezing is better than refrigeration. However, charging a frozen battery can result in an explosion. The removal of advice to freeze the battery is to protect the user, not the battery.

The lower the state of charge, the better for battery storage. The reason 40% is given as the desirable is, once again, to protect the user. If the battery happens to drop "below zero", so that the keep-alive circuit is interrupted, the battery circuitry will permanently disable the battery.

Some batteries which I closely monitor are kept at ~20% charge. Because the laptops are woken up monthly to check for software updates, they are protected from the above.

[Cigarguy]

A time machine is the best device. Failing that use it, store it, stare at it at normal temperature knowing that time will eventually and more rapidly than we like will kill it. When it's no good anymore replace with new and repeat.