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Batteries

Latest revision as of 02:51, 22 November 2011

All the Nokia tablets use lithium-ion batteries, which have specific requirements for care to maintain optimal battery longevity.

Warning: do not buy cheap replacement Nokia batteries from ebay or other such sites. Most of these batteries are fakes and come with a much lower capacity than advertised.

[edit] Li-ion Battery Summary

[edit] Charging, Storage and Usage

[edit] Memory Effect

Li-ion batteries do not suffer from the memory effect. They have a low self-discharge rate of approximately 5% per month, compared with over 30% per month in nickel metal hydride batteries and 10% per month in nickel cadmium batteries.

[edit] Lifetime & Capacity Loss

The battery can be charged and discharged hundreds of times but it will eventually wear out. When the operating time (talk-time and standby time) is noticeably shorter than normal, it is time to buy a new battery.

Capacity loss is a function of number of full-discharge cycles since manufacturing, and other stress factors, including over-/under-voltage, over-current, and over-/under-temperature.

[edit] Temperature

Leaving the battery in hot or cold places, such as in a closed car in summer or winter conditions, will reduce the capacity and lifetime of the battery. Always try to keep the battery between 15°C and 25°C (59°F and 77°F). A phone with a hot or cold battery may temporarily not work, even when the battery is fully charged.

Batteries' performance is particularly limited in temperatures well below freezing.

[edit] Storage

Heat affects capacity loss during storage. "Different storage temperatures produce different loss results: 6% loss at 0 °C/32 °F, 20% at 25 °C/77 °F, and 35% at 40 °C/104 °F. When stored at 40% charge level, these figures are reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively."

[edit] Voltage

Voltage ranges from 3.0V (discharged) to 4.2V (charged). 3.7V nominal voltage

[edit] Disposal

Dispose of batteries according to local regulations (e.g. recycling). Do not dispose as household waste.

[edit] Extend Battery Lifetime

• For good operation times with Li-Ion batteries, discharge the battery from time to time by leaving the product switched on until it turns itself off.
• Stay 40-60% charged for storage - around 3.6-3.8V. Unlike Ni-Cd batteries, lithium-ion batteries should be charged early and often. However, if they are not used for a longer time, they should be brought to a charge level of around 40%. Lithium-ion batteries should never be "deep-cycled" like Ni-Cd batteries
• Stay cool. Li-ion batteries should be kept cool. Ideally they are stored in a refrigerator. Aging will take its toll much faster at high temperatures. The high temperatures found in cars cause lithium-ion batteries to degrade rapidly.
• Only buy new batteries when you need them.
• When buying new batteries, try to check the manufacturing date to make sure they really are new.

[edit] Extend Device Run Time

See Make your battery last longer for tips on extending running time on your device.

[edit] Battery Status

There is much more information available about the battery than the charge indicator icon. To get a more precise description of the battery's charge, type

lshal | grep percentage

in the terminal (Open xterm with Ctrl-Shift-x). The lshal (list hardware abstraction layer) command returns a long printout of information about the hardware. Grep is a linux user command that searches input for a specific string and prints the line that it is found in.

To get any information about the battery, type:

lshal -u /org/freedesktop/Hal/devices/bme

The percentage that is returned is relative to the fullest charge the battery has ever sustained, so it will be less than 100 even after recharging, and the highest value it can reach will decrease over time as the battery wears.(See the comments.)