Lithium ion batteries – storage

It is significantly beneficial to avoid storing a lithium-ion battery at full charge. A Li-ion battery stored at 40% charge will last many times longer than one stored at 100% charge, particularly at higher temperatures.

If a Li-ion battery is stored with too low a charge, there is a risk of allowing the charge to drop below the battery’s low-voltage threshold, resulting in an unrecoverable dead battery. Once the charge has dropped to this level, recharging it can be dangerous. Some batteries therefore feature an internal safety circuit which will prevent charging in this state, and the battery will be for all practical purposes dead.

In circumstances where a second Li-ion battery is available for a given device, it is recommended that the unused battery be discharged to 40% and placed in the refrigerator to prolong its shelf life. While the battery can be used or charged immediately, some Li-ion batteries will provide more energy when brought to room temperature.

http://en.wikipedia.org/wiki/Lithium-ion_battery#Storage_temperature_and_charge

Lithium Ion batteries – storing with low charge means a dead battery

If a Li-ion battery is stored with too low a charge, there is a risk of allowing the charge to drop below the battery’s low-voltage threshold, resulting in an unrecoverable dead battery. Once the charge has dropped to this level, recharging it can be dangerous. Some batteries therefore feature an internal safety circuit which will prevent charging in this state, and the battery will be for all practical purposes dead.

http://en.wikipedia.org/wiki/Lithium-ion_battery#Storage_temperature_and_charge

Time Machine: Preparing backup for ages…

Since Leopard I’ve been getting “Preparing backup” messages that have lasted forever whenever I try to backup my system on to an external volume (i.e. my Time Machine disk).

Digging around in the system messages, I found this: “waiting for index to be ready” being repeated endlessly.

The fix appears to be to add your Time Machine disk to the Privacy settings of Spotlight so that it doesn’t get indexed and then reboot.

http://forums.macrumors.com/showthread.php?t=432893

 

Note: I had another issue adding my Time Machine disk to the Privacy settings of Spotlight which is discussed here: 

http://kenjun.wordpress.com/2008/07/18/privacy-list-error-spotlight/